Rapid Visual Screening of Buildings for Potential Seismic Hazards

Rapid Visual Screening ofBuildings for PotentialSeismic HazardsA HandbookFEMA 154, Edition 2 / March 2002FEMA

NATIONAL EARTHQUAKE HAZARDS REDUCTION PROGRAMSecond EditionRAPID VISUAL SCREENING OF BUILDINGSFOR POTENTIAL SEISMIC HAZARDS:A HANDBOOKAPPLIED TECHNOLOGY COUNCIL555 Twin Dolphin Drive, Suite 550Redwood City, California 94065Funded byFEMAWashington, DC

FEMA ForewordThe Federal Emergency Management Agency(FEMA) is pleased to present the second edition ofthe widely used Rapid Visual Screening ofBuildings for Potential Seismic Hazards: AHandbook, and its companion, SupportingDocumentation. The policy of improving reportsand manuals that deal with the seismic safety ofexisting buildings as soon as new information andadequate resources are available is thus beingreaffirmed. Users should take note of some majordifferences between the two editions of theHandbook. The technical content of the newedition is based more on experiential data and lesson expert judgment than was the case in the earlieredition, as is explained in the SupportingDocumentation. From the presentational point ofview, the Handbook retains much of the materialof the earlier edition, but the material has beenrather thoroughly rearranged to further facilitatethe step-by-step process of conducting the rapidvisual screening of a building. By far the mostsignificant difference between the two editions,however, is the need for a higher level ofengineering understanding and expertise on thepart of the users of the second edition. This shifthas been caused primarily by the difficultyexperienced by users of the first edition inidentifying the lateral-force-resisting system of abuilding without entry—a critical decision of therapid visual screening process. The contents ofthe Supporting Documentation volume have alsobeen enriched to reflect the technical advances inthe Handbook.FEMA and the Project Officer wish to expresstheir gratitude to the members of the ProjectAdvisory Panel, to the technical and workshopconsultants, to the project management, and to thereport production and editing staff for theirexpertise and dedication in the upgrading of thesetwo volumes.The Federal Emergency Management AgencyFEMA 154 FEMA Foreword iii

PrefaceIn August 1999 the Federal EmergencyManagement Agency (FEMA) awarded theApplied Technology Council (ATC) a two-yearcontract to update the FEMA 154 report, RapidVisual Screening of Buildings for PotentialSeismic Hazards: A Handbook, and thecompanion FEMA-155 report, Rapid VisualScreening of Buildings for Potential SeismicHazards: Supporting Documentation, both ofwhich were originally published in 1988.The impetus for the project stemmed in partfrom the general recommendation in the FEMA315 report, Seismic Rehabilitation of Buildings:Strategic Plan 2005, to update periodically allexisting reports in the FEMA-developed series onthe seismic evaluation and rehabilitation ofexisting buildings. In addition, a vast amount ofinformation had been developed since 1988,including: (1) new knowledge about theperformance of buildings during damagingearthquakes, including the 1989 Loma Prieta and1994 Northridge earthquakes; (2) new knowledgeabout seismic hazards, including updated nationalseismic hazard maps published by the U. S.Geological Survey in 1996; (3) other new seismicevaluation and damage prediction tools, such asthe FEMA 310 report, Handbook for the SeismicEvaluation of Buildings – a Prestandard, (anupdated version of FEMA 178, NEHRP Handbookfor the Seismic Evaluation of Existing Buildings),and HAZUS, FEMA’s tool for estimating potentiallosses from natural disasters; and (4) experiencefrom the widespread use of the original FEMA154 Handbook by federal, state and municipalagencies, and others.The project included the following tasks:(1) an effort to obtain users feedback, which wasexecuted through the distribution of a voluntaryFEMA 154 Users Feedback Form to organizationsthat had ordered or were known to have usedFEMA 154 (the Feedback Form was also postedon ATC’s web site); (2) a review of availableinformation on the seismic performance ofbuildings, including a detailed review of theHAZUS fragility curves and an effort to correlatethe relationship between results from the use ofboth the FEMA 154 rapid visual screeningprocedure and the FEMA 178 detailed seismicevaluation procedures on the same buildings;(3) a Users Workshop midway in the project tolearn first hand the problems and successes oforganizations that had used the rapid visualscreening procedure on buildings under theirjurisdiction; (4) updating of the original FEMA154 Handbook to create the second edition; and(5) updating of the original FEMA 155 SupportingDocumentation report to create the second edition.This second edition of the FEMA 154Handbook provides a standard rapid visualscreening procedure to identify, inventory, andrank buildings that are potentially seismicallyhazardous. The scoring system has been revised,based on new information, and the Handbook hasbeen shortened and focused to facilitateimplementation. The technical basis for the rapidvisual screening procedure, including a summaryof results from the efforts to solicit user feedback,is documented in the companion second edition ofthe FEMA 155 report, Rapid Visual Screening ofBuildings for Potential Seismic Hazards:Supporting Documentation.ATC gratefully acknowledges the personnelinvolved in developing the second editions of theFEMA 154 and FEMA 155 reports. CharlesScawthorn served as Co-Principal Investigator andProject Director. He was assisted by Kent David,Vincent Prabis, Richard A. Ranous, and NileshShome, who served as Technical Consultants.Members of the Project Advisory Panel, whoprovided overall review and guidance for theproject, were: Thalia Anagnos, John Baals, JamesR. Cagley (ATC Board Representative), MelvynGreen, Terry Hughes, Anne S. Kiremidjian, JoanMacQuarrie, Chris D. Poland, Lawrence D.Reaveley, Doug Smits, and Ted Winstead.William T. Holmes served as facilitator for theUsers Workshop, and Keith Porter served asrecorder. Stephanie A. King verified the BasicStructural Hazard Scores and the Score Modifiers.A. Gerald Brady, Peter N. Mork, and MichelleSchwartzbach provided report editing andproduction services. The affiliations of theseindividuals are provided in the list of projectparticipants.ATC also gratefully acknowledges thevaluable assistance, support, and cooperationprovided by Ugo Morelli, FEMA Project Officer.In addition, ATC acknowledges participants in theFEMA 154 Preface v

FEMA 154 Users Workshop, which included, inaddition to the project personnel listed above, thefollowing individuals: Al Berstein, U. S. Bureauof Reclamation; Amitabha Datta, General ServicesAdministration; Ben Emam, Amazon.com;Richard K. Eisner, California Office of EmergencyServices; Ali Fattah, City of San Diego; BrianKehoe, Wiss Janney Elstner Associates, Inc.;David Leung, City and County of San Francisco;Douglas McCall, Marx/Okubo; Richard Silva,National Park Service; Howard Simpson, SimpsonGumpertz & Heger Inc.; Steven Sweeney, U. S.Army Civil Engineering Research Laboratory;Christine Theodooropoulos, University of Oregon;and Zan Turner, City and County of SanFrancisco. Those persons who responded toATC’s request to complete the voluntary FEMA154 Users Feedback form are also gratefullyacknowledged.Christopher Rojahn, Principal InvestigatorATC Executive Directorvi Preface FEMA 154

Summary and ApplicationThis FEMA 154 Report, Rapid Visual Screeningof Buildings for Potential Seismic Hazards: AHandbook, is the first of a two-volume publicationon a recommended methodology for rapid visualscreening of buildings for potential seismichazards. The technical basis for the methodology,including the scoring system and its development,are contained in the companion FEMA 155 report,Rapid Visual Screening of Buildings for PotentialSeismic Hazards: Supporting Documentation.Both this document and the companion documentare second editions of similar documentspublished by FEMA in 1988.The rapid visual screening procedure (RVS)has been developed for a broad audience,including building officials and inspectors, andgovernment agency and private-sector buildingowners (hereinafter, the "RVS authority"), toidentify, inventory, and rank buildings that arepotentially seismically hazardous. Although RVSis applicable to all buildings, its principal purposeis to identify (1) older buildings designed andconstructed before the adoption of adequateseismic design and detailing requirements, (2)buildings on soft or poor soils, or (3) buildingshaving performance characteristics that negativelyinfluence their seismic response. Once identifiedas potentially hazardous, such buildings should befurther evaluated by a design professionalexperienced in seismic design to determine if, infact, they are seismically hazardous.The RVS uses a methodology based on a“sidewalk survey” of a building and a DataCollection Form, which the person conducting thesurvey (hereafter referred to as the screener)completes, based on visual observation of thebuilding from the exterior, and if possible, theinterior. The Data Collection Form includes spacefor documenting building identificationinformation, including its use and size, aphotograph of the building, sketches, anddocumentation of pertinent data related to seismicperformance, including the development of anumeric seismic hazard score.Once the decision to conduct rapid visualscreening for a community or group of buildingshas been made by the RVS authority, thescreening effort can be expedited by pre-planning,including the training of screeners, and carefuloverall management of the process.Completion of the Data Collection Form in thefield begins with identifying the primary structurallateral-load-resisting system and structuralmaterials of the building. Basic Structural HazardScores for various building types are provided onthe form, and the screener circles the appropriateone. For many buildings, viewed only from theexterior, this important decision requires thescreener to be trained and experienced in buildingconstruction. The screener modifies the BasicStructural Hazard Score by identifying andcircling Score Modifiers, which are related toobserved performance attributes, and which arethen added (or subtracted) to the Basic StructuralHazard Score to arrive at a final Structural Score,S. The Basic Structural Hazard Score, ScoreModifiers, and final Structural Score, S, all relateto the probability of building collapse, shouldsevere ground shaking occur (that is, a groundshaking level equivalent to that currently used inthe seismic design of new buildings). Final Sscores typically range from 0 to 7, with higher Sscores corresponding to better expected seismicperformance.Use of the RVS on a community-wide basisenables the RVS authority to divide screenedbuildings into two categories: those that areexpected to have acceptable seismic performance,and those that may be seismically hazardous andshould be studied further. An S score of 2 issuggested as a “cut-off”, based on present seismicdesign criteria. Using this cut-off level, buildingshaving an S score of 2 or less should beinvestigated by a design professional experiencedin seismic design.The procedure presented in this Handbook ismeant to be the preliminary screening phase of amulti-phase procedure for identifying potentiallyhazardous buildings. Buildings identified by thisprocedure must be analyzed in more detail by anexperienced seismic design professional. Becauserapid visual screening is designed to be performedfrom the street, with interior inspection not alwayspossible, hazardous details will not always bevisible, and seismically hazardous buildings maynot be identified as such. Conversely, buildingsinitially identified as potentially hazardous byRVS may prove to be adequate.FEMA 154 Summary and Application vii

ContentsFEMA Foreword................................................................................................................................................ iiiPreface .................................................................................................................................................................vSummary and Application ................................................................................................................................ viiList of Figures.................................................................................................................................................. xiiiList of Tables ....................................................................................................................................................xixIllustration Credits ............................................................................................................................................xxi1. Introduction ...................................................................................................................................................11.1 Background..........................................................................................................................................11.2 Screening Procedure Purpose, Overview, and Scope..........................................................................21.3 Companion FEMA 155 Report............................................................................................................31.4 Relationship of FEMA 154 to Other Documents in the FEMA Existing Building Series ..................41.5 Uses of RVS Survey Results ...............................................................................................................41.6 How to Use this Handbook..................................................................................................................42. Planning and Managing Rapid Visual Screening..........................................................................................52.1 Screening Implementation Sequence...................................................................................................52.2 Budget Development and Cost Estimation..........................................................................................62.3 Pre-Field Planning ...............................................................................................................................62.4 Selection and Review of the Data Collection Form ............................................................................72.4.1 Determination of Seismicity Region ......................................................................................82.4.2 Determination of Key Seismic Code Adoption Dates and Other Considerations ..................82.4.3 Determination of Cut-Off Score ...........................................................................................102.5 Qualifications and Training for Screeners.........................................................................................112.6 Acquisition and Review of Pre-Field Data........................................................................................112.6.1 Assessor’s Files ....................................................................................................................112.6.2 Building Department Files....................................................................................................122.6.3 Sanborn Maps.......................................................................................................................122.6.4 Municipal Databases.............................................................................................................152.6.5 Previous Studies ...................................................................................................................152.6.6 Soils Information ..................................................................................................................152.7 Review of Construction Documents..................................................................................................172.8 Field Screening of Buildings .............................................................................................................182.9 Checking the Quality and Filing the Field Data in the Record-Keeping System ..............................183. Completing the Data Collection Form ........................................................................................................193.1 Introduction .......................................................................................................................................193.2 Verifying and Updating the Building Identification Information......................................................203.2.1 Number of Stories.................................................................................................................203.2.2 Year Built .............................................................................................................................203.2.3 Screener Identification..........................................................................................................203.2.4 Total Floor Area ...................................................................................................................213.3 Sketching the Plan and Elevation Views ...........................................................................................213.4 Determining Soil Type ......................................................................................................................213.5 Determining and Documenting Occupancy.......................................................................................223.5.1 Occupancy ............................................................................................................................223.5.2 Occupancy Load...................................................................................................................23FEMA 154 Contents ix

3.6 Identifying Potential Nonstructural Falling Hazards.........................................................................233.7 Identifying the Lateral-Load-Resisting System and Documenting the Related BasicStructural Score .................................................................................................................................243.7.1 Fifteen Building Types Considered by the RVS Procedure and Related BasicStructural Scores...................................................................................................................243.7.2 Identifying the Lateral-Force-Resisting System...................................................................253.7.3 Interior Inspections...............................................................................................................363.7.4 Screening Buildings with More Than One Lateral-Force Resisting System........................373.8 Identifying Seismic Performance Attributes and Recording Score Modifiers ..................................383.8.1 Mid-Rise Buildings...............................................................................................................383.8.2 High-Rise Buildings .............................................................................................................383.8.3 Vertical Irregularity ..............................................................................................................383.8.4 Plan Irregularity....................................................................................................................403.8.5 Pre-Code ...............................................................................................................................403.8.6 Post-Benchmark....................................................................................................................413.8.7 Soil Type C, D, or E .............................................................................................................413.9 Determining the Final Score..............................................................................................................413.10 Photographing the Building...............................................................................................................423.11 Comments Section.............................................................................................................................424. Using the RVS Procedure Results...............................................................................................................434.1 Interpretation of RVS Score ..............................................................................................................434.2 Selection of RVS “Cut-Off” Score....................................................................................................434.3 Prior Uses of the RVS Procedure ......................................................................................................444.4 Other Possible Uses of the RVS Procedure.......................................................................................454.4.1 Using RVS Scores as a Basis for Hazardous Building Mitigation Programs.......................454.4.2 Using RVS Data in Community Building Inventory Development .....................................464.4.3 Using RVS Data to Plan Postearthquake Building-Safety-Evaluation Efforts.....................464.4.4 Resources Needed for the Various Uses of the RVS Procedure...........................................465. Example Application of Rapid Visual Screening........................................................................................495.1 Step 1: Budget and Cost Estimation .................................................................................................495.2 Step 2: Pre-Field Planning................................................................................................................505.3 Step 3: Selection and Review of the Data Collection Form .............................................................505.4 Step 4: Qualifications and Training for Screeners............................................................................515.5 Step 5: Acquisition and Review of Pre-Field Data...........................................................................515.6 Step 6: Review of Construction Documents.....................................................................................555.7 Step 7: Field Screening of Buildings................................................................................................555.8 Step 8: Transferring the RVS Field Data to the Electronic Building RVS Database .......................64Appendix A: Maps Showing Seismicity Regions.............................................................................................65Appendix B: Data Collection Forms and Quick Reference Guide ...................................................................77Appendix C: Review of Design and Construction Drawings ...........................................................................83Appendix D: Exterior Screening for Seismic System and Age ........................................................................85D.1 Introduction .......................................................................................................................................85D.2 What to Look for and How to Find It................................................................................................85D.3 Identification of Building Age...........................................................................................................85D.4 Identification of Structural Type .......................................................................................................88D.5 Characteristics of Exposed Construction Materials...........................................................................95Appendix E: Characteristics and Earthquake Performance of RVS Building Types........................................99E.1 Introduction .......................................................................................................................................99E.2 Wood Frame (W1, W2) .....................................................................................................................99x Contents FEMA 154

E.2.1 Characteristics ......................................................................................................................99E.2.2 Typical Earthquake Damage ..............................................................................................100E.2.3 Common Rehabilitation Techniques ..................................................................................102E.3 Steel Frames (S1, S2) ......................................................................................................................103E.3.1 Characteristics ....................................................................................................................103E.3.2 Typical Earthquake Damage ..............................................................................................105E.3.3 Common Rehabilitation Techniques ..................................................................................105E.4 Light Metal (S3) ..............................................................................................................................106E.4.1 Characteristics ....................................................................................................................106E.4.2 Typical Earthquake Damage ..............................................................................................107E.5 Steel Frame with Concrete Shear Wall (S4)....................................................................................107E.5.1 Characteristics ....................................................................................................................107E.5.2 Typical Earthquake Damage ..............................................................................................108E.6 Steel Frame with Unreinforced Masonry Infill (S5)........................................................................108E.6.1 Characteristics ....................................................................................................................108E.6.2 Typical Earthquake Damage ..............................................................................................109E.6.3 Common Rehabilitation Techniques ..................................................................................110E.7 Concrete Moment-Resisting Frame (C1).........................................................................................110E.7.1 Characteristics ....................................................................................................................110E.7.2 Typical Earthquake Damage ..............................................................................................112E.7.3 Common Rehabilitation Techniques ..................................................................................113E.8 Concrete Shear Wall (C2)................................................................................................................113E.8.1 Characteristics ....................................................................................................................113E.8.2 Typical Types of Earthquake Damage ...............................................................................114E.8.3 Common Rehabilitation......................................................................................................114E.9 Concrete Frame with Unreinforced Masonry Infill (C3).................................................................114E.9.1 Characteristics ....................................................................................................................114E.9.2 Typical Earthquake Damage ..............................................................................................116E.9.3 Common Rehabilitation Techniques ..................................................................................116E.10 Tilt-up Structures (PC1) ..................................................................................................................116E.10.1 Characteristics ....................................................................................................................116E.10.2 Typical Earthquake Damage ..............................................................................................117E.10.3 Common Rehabilitation Techniques ..................................................................................118E.11 Precast Concrete Frame (PC2).........................................................................................................118E.11.1 Characteristics ....................................................................................................................118E.11.2 Typical Earthquake Damage ..............................................................................................120E.11.3 Common Rehabilitation Techniques ..................................................................................120E.12 Reinforced Masonry (RM1 and RM2) ............................................................................................121E.12.1 Characteristics ....................................................................................................................121E.12.2 Typical Earthquake Damage ..............................................................................................121E.12.3 Common Rehabilitation Techniques ..................................................................................121E.13 Unreinforced Masonry (URM)........................................................................................................122E.13.1 Characteristics ....................................................................................................................122E.13.2 Typical Earthquake Damage ..............................................................................................126E.13.3 Common Rehabilitation Techniques ..................................................................................126Appendix F: Earthquakes and How Buildings Resist Them...........................................................................129F.1 The Nature of Earthquakes ..............................................................................................................129F.2 Seismicity of the United States........................................................................................................130F.3 Earthquake Effects...........................................................................................................................131F.4 How Buildings Resist Earthquakes .................................................................................................134References........................................................................................................................................................137Project Participants ..........................................................................................................................................139FEMA 154 Contents xi

List of FiguresFigure 1-1Figure 1-2High, moderate, and low seismicity regions of the conterminous United States. Adifferent RVS Data Collection Form has been developed for each of these regions.................1Data Collection Forms for the three designated seismicity regions (low, moderate,and high). ...................................................................................................................................3Figure 2-1 Rapid visual screening implementation sequence. ....................................................................5Figure 2-2Figure 2-3Figure 2-4Example RVS Data Collection Form (high seismicity).............................................................7Sections 1 and 2 of Quick Reference Guide (for use with Data Collection Form)..................10Building identification portion of RVS Data Collection Form................................................11Figure 2-5 Example Sanborn map showing building information for a city block. ..................................12Figure 2-6 Key to Sanborn map symbols. ...............................................................................................13Figure 2-7Sanborn map and corresponding aerial photograph of a city block.........................................14Figure 2-8 Photographs of elevation views of buildings shown in Figure 2-7..........................................15Figure 2-9Figure 2-10Figure 3-1Examples of in-house screen displays of municipal databases................................................16Location on Data Collection Form where soil type information is recorded...........................17Example RVS Data Collection Form (high seismicity)...........................................................19Figure 3-2 Portion of Data Collection Form for documenting building identification. ............................20Figure 3-3Figure 3-4Figure 3-5Sample Data Collection Form showing location for sketches of building plan andelevation views. .......................................................................................................................21Location on Data Collection Form where soil type information is documented (circled).......21Occupancy portion of Data Collection Form...........................................................................22Figure 3-6 Portion of Data Collection Form for documenting nonstructural falling hazards. ..................23Figure 3-7 Portion of Data Collection Form containing Basic Structural Hazard Scores. ........................25Figure 3-8Figure 3-9Typical frame structure. Features include: large window spans, window openings onmany sides, and clearly visible column-beam grid pattern......................................................35Typical bearing wall structure. Features include small window span, at least twomostly solid walls, and thick load-bearing walls. ....................................................................35Figure 3-10 Frame and bearing wall structures ...........................................................................................36Figure 3-11Interior view showing fireproofed columns and beams, which indicate a steel building(S1, S2, or S4)..........................................................................................................................37FEMA 154 List of Figures xiii

Figure 3-12Figure 3-13Figure 3-14Interior view showing concrete columns and girders, which indicate a concrete momentframe (C1). .............................................................................................................................. 37Portion of Data Collection Form containing attributes that modify performance andassociated score modifiers....................................................................................................... 38Elevation views showing vertical irregularities, with arrows indicating locationsof particular concern................................................................................................................ 39Figure 3-15 Example of setbacks and a soft first story ............................................................................... 39Figure 3-16Figure 3-17Example of soft story conditions, where parking requirements result in largeweak openings. ........................................................................................................................ 40Plan views of various building configurations showing plan irregularities; arrowsindicate possible areas of damage. .......................................................................................... 40Figure 3-18 Example of a building, with a plan irregularity, with two wings meeting at right angles....... 41Figure 3-19 Example of a building, triangular in plan, subject to torsion. ................................................. 41Figure 3-20Figure 5-1Location on Data Collection Form where the final score, comments, and an indicationif the building needs detailed evaluation are documented....................................................... 42Screen capture of USGS web page showing SA values for 0.2 sec and 1.0 sec for groundmotions having 2% probability of being exceeded in 50 years............................................... 50Figure 5-2 High seismicity Data Collection Form selected for Anyplace, USA ...................................... 52Figure 5-3Quick Reference Guide for Anyplace USA showing entries for years in which seismiccodes were first adopted and enforced and benchmark years. ................................................ 53Figure 5-4 Property information at example site in city’s geographic information system...................... 54Figure 5-5 Exterior view of 3703 Roxbury Street .................................................................................... 56Figure 5-6 Close-up view of 3703 Roxbury Street exterior showing perimeter braced steel framing...... 56Figure 5-7 Building identification portion of Data Collection Form for Example 1,3703 Roxbury Street................................................................................................................ 56Figure 5-8 Completed Data Collection Form for Example 1, 3703 Roxbury Street................................. 57Figure 5-9 Exterior view of 3711 Roxbury............................................................................................... 58Figure 5-10Close-up view of 3711 Roxbury Street building exterior showing infillframe construction................................................................................................................... 58Figure 5-11 Completed Data Collection Form for Example 2, 3711 Roxbury Street................................. 59Figure 5-12 Exterior view of 5020 Ebony Drive ........................................................................................ 60Figure 5-13 Completed Data Collection Form for Example 3, 5020 Ebony Drive .................................... 61Figure 5-14 Exterior view of 1450 Addison Avenue.................................................................................. 62xiv List of Figures FEMA 154

Figure 5-15Building identification portion of Data Collection Form for Example 4, 1450 AddisonAvenue.....................................................................................................................................62Figure 5-16 Completed Data Collection Form for Example 4, 1450 Addison Avenue ..............................62Figure A-1 Seismicity Regions of the Conterminous United States ..........................................................66Figure A-2Figure A-3Figure A-4Figure A-5Figure A-6Seismicity Regions in California, Idaho, Nevada, Oregon, and Washington..........................67Seismicity Regions in Arizona, Montana, Utah, and Wyoming..............................................68Seismicity Regions in Colorado, Kansas, New Mexico, Oklahoma, and Texas......................69Seismicity Regions in Iowa, Michigan, Minnesota, Nebraska, North Dakota,South Dakota and Wisconsin...................................................................................................70Seismicity Regions in Illinois, Indiana, Kentucky, Missouri, and Ohio..................................71Figure A-7 Seismicity Regions in Alabama, Arkansas, Louisiana, Mississippi, and Tennessee ...............72Figure A-8Figure A-9Seismicity Regions in Connecticut, Maine, Massachusetts, New Hampshire, RhodeIsland, and Vermont.................................................................................................................73Seismicity Regions in Delaware, Maryland, New Jersey, Pennsylvania, Virginia, andWest Virginia...........................................................................................................................74Figure A-10 Seismicity Regions in Florida, Georgia, North Carolina, and South Carolina ........................75Figure A-11 Seismicity Regions in Alaska and Hawaii ...............................................................................76Figure D-1Figure D-2Photos showing basic construction, in steel-frame buildings and reinforcedconcrete-frame buildings. ........................................................................................................91Building with exterior columns covered with a façade material..............................................94Figure D-3 Detail of the column façade of Figure D-2. .............................................................................94Figure D-4 Building with both shear walls (in the short direction) and frames (in the long direction) .....94Figure D-5 Regular, full-height joints in a building’s wall indicate a concrete tilt-up. .............................95Figure D-6 Reinforced masonry wall showing no course of header bricks (a row of visible brick ends). 95Figure D-7Figure D-8Reinforced masonry building with exterior wall of concrete masonry units, or concreteblocks.......................................................................................................................................95A 1970s renovated façade hides a URM bearing-wall structure..............................................95Figure D-9 A concrete shear-wall structure with a 1960s renovated façade. .............................................96Figure D-10Figure D-11URM wall showing header courses (identified by arrows) and two washer platesindicating wall anchors. ...........................................................................................................96Drawing of two types of masonry pattern showing header bricks...........................................96FEMA 154 List of Figures xv

Figure D-12Diagram of common reinforced masonry construction. Bricks are left out of the bottomcourse at intervals to create cleanout holes, then inserted before grouting ............................. 97Figure D-13 Brick veneer panels. ................................................................................................................ 97Figure D-14 Hollow clay tile wall with punctured tiles............................................................................... 97Figure D-15 Sheet metal siding with masonry pattern................................................................................. 97Figure D-16 Asphalt siding with brick pattern. ........................................................................................... 98Figure D-17 Pre-1940 cast-in-place concrete with formwork pattern. ........................................................ 98Figure E-1Figure E-2Single family residence (an example of the W1 identifier, light wood-frame residentialand commercial buildings less than 5000 square feet). ........................................................... 99Larger wood-framed structure, typically with room-width spans (W2, light, wood-framebuildings greater than 5000 square feet). ................................................................................ 99Figure E-3 Drawing of wood stud frame construction. ........................................................................... 100Figure E-4 Stud wall, wood-framed house.............................................................................................. 101Figure E-5 Drawing of timber pole framed house................................................................................... 101Figure E-6 Timber pole framed house..................................................................................................... 101Figure E-7 House off its foundation, 1983 Coalinga earthquake. ........................................................... 101Figure E-8 Failed cripple stud wall, 1992 Big Bear earthquake.............................................................. 102Figure E-9 Failure of post and pier foundation, Humbolt County. ......................................................... 102Figure E-10 Seismic strengthening of a cripple wall, with plywood sheathing. ....................................... 103Figure E-11 Drawing of steel moment-resisting frame building............................................................... 103Figure E-12 Braced frame configurations. ................................................................................................ 104Figure E-13Braced steel frame, with chevron and diagonal braces. The braces and steel frames areusually covered by finish material after the steel is erected. ................................................. 104Figure E-14 Chevron bracing in steel building under construction........................................................... 104Figure E-15 Rehabilitation of a concrete parking structure using exterior X-braced steel frames............ 105Figure E-16 Use of a braced frame to rehabilitate an unreinforced masonry building.............................. 106Figure E-17 Drawing of light metal construction...................................................................................... 106Figure E-18 Connection of metal siding to light metal frame with rows of screws (encircled)................ 107Figure E-19 Prefabricated metal building (S3, light metal building). ....................................................... 107Figure E-20 Drawing of steel frame with interior concrete shear-walls.................................................... 108xvi List of Figures FEMA 154

Figure E-21 Concrete shear wall on building exterior. ..............................................................................108Figure E-22Figure E-23Close-up of exterior shear wall damage during a major earthquake......................................108Drawing of steel frame with URM infill................................................................................109Figure E-24 Example of steel frame with URM infill walls (S5). .............................................................110Figure E-25 Drawing of concrete moment-resisting frame building .........................................................111Figure E-26 Extreme example of ductility in concrete, 1994 Northridge earthquake. ..............................111Figure E-27Figure E-28Figure E-29Figure E-30Figure E-31Figure E-32Figure E-33Figure E-34Figure E-35Example of ductile reinforced concrete column, 1994 Northridge earthquake; horizontalties would need to be closer for greater demands. .................................................................112Concrete moment-resisting frame building (C1) with exposed concrete, deep beams,wide columns (and with architectural window framing) .......................................................112Locations of failures at beam-to-column joints in nonductile frames, 1994 Northridgeearthquake..............................................................................................................................113Drawing of concrete shear-wall building...............................................................................114Tall concrete shear-wall building: walls connected by damaged spandrel beams................115Shear-wall damage, 1989 Loma Prieta earthquake................................................................115Concrete frame with URM infill............................................................................................115Blow-up (lower photo) of distant view of C3 building (upper photo) showing concreteframe with URM infill (left wall), and face brick (right wall)...............................................115Drawing of tilt-up construction typical of the western United States. Tilt-upconstruction in the eastern United States may incorporate a steel frame...............................116Figure E-36 Tilt-up industrial building, 1970s. .........................................................................................117Figure E-37Figure E-38Figure E-39Tilt-up industrial building, mid- to late 1980s.......................................................................117Tilt-up construction anchorage failure...................................................................................117Result of failure of the roof beam anchorage to the wall in tilt-up building..........................117Figure E-40 Newly installed anchorage of roof beam to wall in tilt-up building. .....................................118Figure E-41Drawing of precast concrete frame building..........................................................................119Figure E-42 Typical precast column cover on a steel or concrete moment frame. ....................................120Figure E-43Figure E-44Exposed precast double-T sections and overlapping beams are indicative ofprecast frames ........................................................................................................................120Example of precast double-T section during installation.......................................................120FEMA 154 List of Figures xvii

Figure E-45Precast structural cross; installation joints are at sections where bending is minimumduring high seismic demand.................................................................................................. 120Figure E-46 Modern reinforced brick masonry......................................................................................... 121Figure E-47 Drawing of unreinforced masonry bearing-wall building, 2-story........................................ 122Figure E-48 Drawing of unreinforced masonry bearing-wall building, 4-story........................................ 123Figure E-49 Drawing of unreinforced masonry bearing-wall building, 6-story........................................ 124Figure E-50 East coast URM bearing-wall building. ................................................................................ 124Figure E-51 West coast URM bearing-wall building................................................................................ 124Figure E-52 Drawings of typical window head features in URM bearing-wall buildings. ....................... 125Figure E-53Parapet failure leaving an uneven roof line, due to inadequate anchorage, 1989 LomaPrieta earthquake. .................................................................................................................. 126Figure E-54 Damaged URM building, 1992 Big Bear earthquake............................................................ 126Figure E-55Figure F-1Figure F-2Figure F-3Upper: Two existing anchors above three new wall anchors at floor line usingdecorative washer plates. Lower: Rehabilitation techniques include closely spacedanchors at floor and roof levels. ............................................................................................ 127The separate tectonic plates comprising the earth’s crust superimposed on a map ofthe world................................................................................................................................ 129Seismicity of the conterminous United States 1977-1997. This reproduction showsearthquake locations without regard to magnitude or depth. The San Andreas fault andother plate boundaries are indicated with white lines............................................................ 131Seismicity of Alaska 1977 – 1997. The white line close to most of the earthquakes isthe plate boundary, on the ocean floor, between the Pacific and North America plates. ...... 132Figure F-4 Seismicity of Hawaii 1977 – 1997. ...................................................................................... 132.Figure F-5 Mid-rise building collapse, 1985 Mexico City earthquake. .................................................. 133Figure F-6Near-field effects, 1992 Landers earthquake, showing house (white arrow) close tosurface faulting (black arrow); the insert shows a house interior.......................................... 134Figure F-7 Collapsed chimney with damaged roof, 1987 Whittier Narrows earthquake........................ 134Figure F-8 House that slid off foundation, 1994 Northridge earthquake. ............................................... 135Figure F-9Collapsed cripple stud walls dropped this house to the ground, 1992 Landers and BigBear earthquakes. .................................................................................................................. 135Figure F-10 This house has settled to the ground due to collapse of its post and pier foundation............ 135Figure F-11 Collapse of unreinforced masonry bearing wall, 1933 Long Beach earthquake................... 135Figure F-12 Collapse of a tilt-up bearing wall, 1994 Northridge earthquake. .......................................... 135xviii List of Figures FEMA 154

List of TablesTable 2-1Regions of Seismicity with Corresponding Spectral Acceleration Response(from FEMA 310)......................................................................................................................8Table 2-2 Benchmark Years for RVS Procedure Building Types (from FEMA 310). ..............................9Table 2-3Table 2-4Table 3-1Table 4-1Table D-1Checklist of Issues to be Considered During Pre-Field Work Review of the DataCollection Form .......................................................................................................................10Checklist of Field Equipment Needed for Rapid Visual Screening.........................................18Build Type Descriptions, Basic Structural Hazard Scores, and Performance in PastEarthquakes..............................................................................................................................26Matrix of Personnel and Material Resources Needed for Various FEMA 154 RVSApplications.............................................................................................................................47Photographs, Architectural Characteristics, and Age of Residential Buildings.......................86Table D-2 Illustrations, Architectural Characteristics, and Age of Commercial Structures .....................87Table D-3Photographs, Architectural Characteristics, and Age of Miscellaneous Structures.................90Table D-4 Most Likely Structural Types for Pre-1930 Buildings ............................................................92Table D-5Table D-6Table D-7Most Likely Structural Types for 1930-1945 Buildings..........................................................92Most Likely Structural Types for 1945-1960 Buildings..........................................................93Most Likely Structural Types for Post-1960 Buildings...........................................................93FEMA 154 List of Tables xix

Illustration CreditsFiguresCredit1-1, A-1 to 11 Maps credited to Nilesh Shome / ABS Consulting / EQE Engineers / USGS5-5, 6, 12, 14, F-11 Richard Ranous / ABS Consulting / EQE Engineers2-1,8;Charles Scawthorn / ABS Consulting / EQE Engineers3-10 to 12, 15, 16, 18, 19;Table 3-1, Building TypeW1, W2, S1 to S5, C1 toC3, PC1 (top), PC2,RM1, RM2, URM;5-9, 10,D-1 to 5;E-1, 2, 4, 6 to 10, 13 to 16,17 to 19, 21, 22, 24, 26 to29, 32 to 34, 36 to 40, 42,44, 46, 50, 51, 53 to 55;F-5 to 10, 12;Table D-1c to e; Table D-2b to o; Table D-3a to e, h2-5, 6, 7 Sanborn Maps2-9 Oakland, California and Mecklenberg County, North Carolina, web pages3-8, 9; E-43, 45 Drawings by Kit Wong5-1, F-1 to 4 USGS web site5-3 Los Angeles/San Pedro, California; city GISD-6, 8, 9, 10Photographs by Kit WongD-13 to 17; Table D-1a, b;Table D-3f, gD-7 Robert BruceD-11, 12Allen, E., 1985, Fundamentals of Building Construction and Methods, JohnWiley and sons, New York.E-3, 23, 25,30;E-35, 41, 47, 48, 49E-5, 12E-11, 20Lagorio, H., Friedman, H., and K. Wong (1986). Issues for SeismicStrengthening of Existing Buildings: A Practical Guide for Architects.Center for Environmental Design, University of California at Berkeley.Drawing from National Multihazard Survey Instructions. FEMA, TR-84.Steinbrugge, K. (1982). Earthquakes, Volcanoes, and Tsunamis, AnAnatomy of Hazards. Skandia American Group, New York.E-31 James StrattaE-52 Ramsay/Sleeper Architectural Graphic Standards, Seventh Edition (1981).R.T. Packard, AIA, ed., John Wiley & Sons, New York.Table D-2aA Field Guide to American Architecture (1980), The New AmericanLibrary, Inc., New York.Table 3-1, Building Type Earthquake Engineering Research Institute.PC1 (lower)E-39 Anonymous, but greatly appreciatedFEMA-154 Illustration Credits xxi

Chapter 1Introduction1.1 BackgroundRapid visual screening of buildings for potentialseismic hazards, as described herein, originated in1988 with the publication of the FEMA 154Report, Rapid Visual Screening of Buildings forPotential Seismic Hazards: A Handbook. Writtenfor a broad audience ranging from engineers andbuilding officials to appropriately trainednonprofessionals, the Handbook provided a“sidewalk survey” approach that enabled users toclassify surveyed buildings into two categories:those acceptable as to risk to life safety or thosethat may be seismically hazardous and should beevaluated in more detail by a design professionalexperienced in seismic design.During the decade following publication of thefirst edition of the FEMA 154 Handbook, the rapidvisual screening (RVS) procedure was used byprivate-sector organizations and governmentagencies to evaluate more than 70,000 buildingsnationwide (ATC, 2002). This widespreadapplication provided important information aboutthe purposes for which the documentwas used, the ease-of-use of thedocument, and perspectives on theaccuracy of the scoring system uponwhich the procedure was based.Concurrent with the widespreaduse of the document, damagingearthquakes occurred in Californiaand elsewhere, and extensiveresearch and development effortswere carried out under the NationalEarthquake Hazards ReductionProgram (NEHRP). These effortsyielded important new data on theperformance of buildings inearthquakes, and on the expecteddistribution, severity, and occurrenceof earthquake-induced groundshaking.The data and informationgathered during the first decade afterpublication (experience in applyingthe original Handbook, new buildingearthquake performance data, andnew ground shaking information)Figure 1-1have been used to update and improve the rapidvisual screening procedure provided in this secondedition of the FEMA 154 Report, Rapid VisualScreening of Buildings for Potential SeismicHazards: A Handbook. The revised RVSprocedure retains the same framework andapproach of the original procedure, butincorporates a revised scoring system compatiblewith the ground motion criteria in the FEMA 310Report, Handbook for Seismic Evaluation ofBuildings—A Prestandard (ASCE, 1998), and thedamage estimation data provided in the recentlydeveloped FEMA-funded HAZUS damage andloss estimation methodology (NIBS, 1999). As inthe original Handbook, a Data Collection Form isprovided for each of three seismicity regions: low,moderate, and high. However, the boundaries ofthe low, moderate, and high seismicity regions inthe original Handbook have been modified (Figure1-1), reflecting new knowledge on the expecteddistribution, severity, and occurrence ofearthquake ground shaking, and a change in theNote: Seismicity regions are based on ground motions havinga 2% probability of exceedance in 50 years.High, moderate, and low seismicity regions of the conterminousUnited States. A different RVS Data Collection Form has beendeveloped for each of these regions. Enlarged maps are availablein Appendix A.FEMA-154 1: Introduction 1

ecurrence interval considered, from a 475-yearaverage return period (corresponding to groundmotions having a 10% probability of exceedancein 50 years) to a 2475-year average return period(corresponding to ground motions having a 2%probability of excedance in 50 years).This second edition of the FEMA 154Handbook has been shortened and focused tofacilitate implementation. Other improvementsinclude:• guidance on planning and managing an RVSsurvey, including the training of screeners andthe acquisition of data from assessor files andother sources to obtain more reliableinformation on age, structural system, andoccupancy;• more guidance for identifying the structural(lateral-load-resisting) system in the field;• the use of interior inspection or pre-surveyreviews of building plans to identify (orverify) a building’s lateral-load-resistingsystem;• updated Basic Structural Hazard Scores andScore Modifiers that are derived fromanalytical calculations and recently developedHAZUS fragility curves for the modelbuilding types considered by the RVSmethodology;• the use of new seismic hazard information thatis compatible with seismic hazard criteriaspecified in other related FEMA documents(see Section 1.4 below); and• a revised Data Collection Form that providesspace for documenting soil type, additionaloptions for documenting falling hazards, andan expanded list of occupancy types.1.2 Screening Procedure Purpose,Overview, and ScopeThe RVS procedure presented in this Handbookhas been formulated to identify, inventory, andrank buildings that are potentially seismicallyhazardous. Developed for a broad audience thatincludes building officials and inspectors,government agencies, design professionals,private-sector building owners (particularly thosethat own or operate clusters or groups ofbuildings), faculty members who use the RVSprocedure as a training tool, and informedappropriately trained, members of the public, theRVS procedure can be implemented relativelyquickly and inexpensively to develop a list ofpotentially hazardous buildings without the highcost of a detailed seismic analysis of individualbuildings. If a building receives a high score (i.e.,above a specified cut-off score, as discussed laterin this Handbook), the building is considered tohave adequate seismic resistance. If a buildingreceives a low score on the basis of this RVSprocedure, it should be evaluated by a professionalengineer having experience or training in seismicdesign. On the basis of this detailed inspection,engineering analyses, and other detailedprocedures, a final determination of the seismicadequacy and need for rehabilitation can be made.During the planning stage, which is discussedin Chapter 2, the organization that is conductingthe RVS procedure (hereinafter, the “RVSauthority”) will need to specify how the resultsfrom the survey will be used. If the RVS authoritydetermines that a low score automatically requiresthat further study be performed by a professionalengineer, then some acceptable level ofqualification held by the inspectors performing thescreening will be necessary. RVS projects have awide range of goals and they have constraints onbudget, completion date and accuracy, which mustbe considered by the RVS authority as it selectsqualification requirements of the screeningpersonnel. Under most circumstances, a wellplannedand thorough RVS project will requireengineers to perform the inspections. In any case,the program should be overseen by a designprofessional knowledgeable in seismic design forquality assurance purposes.The RVS procedure in this Handbook isdesigned to be implemented without performingstructural analysis calculations. The RVSprocedure utilizes a scoring system that requiresthe user to (1) identify the primary structurallateral-load-resisting system; and (2) identifybuilding attributes that modify the seismicperformance expected of this lateral-load-resistingsystem. The inspection, data collection, anddecision-making process typically will occur at thebuilding site, taking an average of 15 to 30minutes per building (30 minutes to one hour ifaccess to the interior is available). Results arerecorded on one of three Data Collection Forms(Figure 1-2), depending on the seismicity of theregion being surveyed. The Data Collection Form,described in greater detail in Chapter 3, includesspace for documenting building identificationinformation, including its use and size, aphotograph of the building, sketches, anddocumentation of pertinent data related to seismicperformance, including the development of a2 1: Introduction FEMA 154

numeric seismic hazard score.The scores are based on averageexpected ground shaking levels forthe seismicity region as well as theseismic design and constructionpractices for that region 1 .Buildings may be reviewed fromthe sidewalk without the benefit ofbuilding entry, structuraldrawings, or structuralcalculations. Reliability andconfidence in building attributedetermination are increased,however, if the structural framingsystem can be verified duringinterior inspection, or on the basisof a review of constructiondocuments.The RVS procedure isintended to be applicablenationwide, for all conventionalbuilding types. Bridges, largetowers, and other non-buildingstructure types, however, are notcovered by the procedure. Due tobudget or other constraints, someRVS authorities may wish torestrict their RVS to identifyingbuilding types that they considerthe most hazardous, such asunreinforced masonry ornonductile concrete buildings.However, it is recommended, atleast initially, that all conventionalbuilding types be considered, andthat elimination of certain buildingtypes from the screening be welldocumented and supported with Figure 1-2office calculations and fieldsurvey data that justify theirelimination. It is possible that, in some cases,even buildings designed to modern codes, such asthose with configurations that induce extremetorsional response and those with abrupt changesin stiffness, may be potentially hazardous.1 Seismic design and construction practices vary byseismicity region, with little or no seismic designrequirements in low seismicity regions, moderateseismic design requirements in moderate seismicityregions, and extensive seismic design requirements inhigh seismicity regions. The requirements also varywith time, and are routinely updated to reflect newknowledge about building seismic performance.Data Collection Forms for the three designatedseismicity regions (low, moderate, and high).1.3 Companion FEMA 155 ReportA companion volume to this report, Rapid VisualScreening of Buildings for Potential SeismicHazards: Supporting Documentation (secondedition) (FEMA 155) documents the technicalbasis for the RVS procedure described in thisHandbook, including the method for calculatingthe Basic Structural Scores and Score Modifiers.The FEMA 155 report (ATC, 2002) alsosummarizes other information considered duringdevelopment of this Handbook, including theefforts to solicit user feedback and a FEMA 154Users Workshop held in September 2000. TheFEMA 155 document is available from FEMA byFEMA 154 1: Introduction 3

dialing 1-800-480-2520 and should be consultedfor any needed or desired supportingdocumentation.1.4 Relationship of FEMA 154 toOther Documents in the FEMAExisting Building SeriesThe FEMA 154 Handbook has been developed asan integral and fundamental part of the FEMAreport series on seismic safety of existingbuildings. It is intended for use by designprofessionals and others to mitigate the damagingeffects of earthquakes on existing buildings. Theseries includes:• FEMA 154 (this handbook), which provides aprocedure that can be rapidly implemented toidentify buildings that are potentiallyseismically hazardous.• FEMA 310, Handbook for Seismic Evaluationof Buildings—A Prestandard (ASCE, 1998),which provides a procedure to inspect in detaila given building to evaluate its seismicresisting capacity (an updated version of theFEMA 178 NEHRP Handbook for the SeismicEvaluation of Existing Buildings [BSSC,1992]). The FEMA 310 Handbook is ideallysuited for use on those buildings identified bythe FEMA 154 RVS procedure as potentiallyhazardous.FEMA 310 is expected to be superseded in2002 by ASCE 31, a standard of the AmericanSociety of Civil Engineers approved by theAmerican National Standards Institute(ANSI). References in this Handbook toFEMA 310 should then refer to ASCE 31.• FEMA 356, Prestandard and Commentary forthe Seismic Rehabilitation of Buildings(ASCE, 2000), which provides recommendedprocedures for the seismic rehabilitation ofbuildings with inadequate seismic capacity, asdetermined, for example, by a FEMA 310 (orFEMA 178) evaluation. The FEMA 356Prestandard is based on the guidance providedin the FEMA 273 NEHRP Guidelines for theSeismic Rehabilitation of Buildings (ATC,1997a), and companion FEMA 274Commentary on the NEHRP Guidelines forthe Seismic Rehabilitation of Buildings (ATC,1997b).1.5 Uses of RVS Survey ResultsWhile the principal purpose of the RVS procedureis to identify potentially seismically hazardousbuildings needing further evaluation, results fromRVS surveys can also be used for other purposes.These include: (1) ranking a community’s (oragency’s) seismic rehabilitation needs; (2)designing seismic hazard mitigation programs fora community (or agency); (3) developinginventories of buildings for use in regionalearthquake damage and loss impact assessments;(4) planning postearthquake building safetyevaluation efforts; and (5) developing buildingspecificseismic vulnerability information forpurposes such as insurance rating, decisionmaking during building ownership transfers, andpossible triggering of remodeling requirementsduring the permitting process. Additionaldiscussion on the use of RVS survey results isprovided in Chapter 4.1.6 How to Use this HandbookThe Handbook has been designed to facilitate theplanning and execution of rapid visual screening.It is assumed that the RVS authority has alreadydecided to conduct the survey, and that detailedguidance is needed for all aspects of the surveyingprocess. Therefore, the main body of theHandbook focuses on the three principal activitiesin the RVS: planning, execution, and datainterpretation. Chapter 2 contains detailedinformation on planning and managing an RVS.Chapter 3 describes in detail how the DataCollection Form should be completed, andChapter 4 provides guidance on interpreting andusing the results from the RVS. Finally, Chapter 5provides several example applications of the RVSprocedure on real buildings.Relevant seismic hazard maps, full-sized DataCollection Forms, including a Quick ReferenceGuide for RVS implementation, guidance forreviewing design and construction drawings, andadditional guidance for identifying a building’sseismic lateral-load-resisting system from thestreet are provided in Appendices A, B, C, and D,respectively. Appendix E provides additionalinformation on the building types considered inthe RVS procedure, and Appendix F provides anoverview of earthquake fundamentals, theseismicity of the United States, and earthquakeeffects.4 1: Introduction FEMA 154

Chapter 2Planning and ManagingRapid Visual ScreeningOnce the decision to conduct rapid visualscreening (RVS) for a community or group ofbuildings has been made by the RVS authority, thescreening effort can be expedited by pre-planningand careful overall management of theprocess. This chapter describes the overallscreening implementation sequence andprovides detailed information on importantpre-planning and management aspects.Instructions on how to complete the DataCollection Form are provided in Chapter 3.screened, selection and development of arecord-keeping system, and compilation anddevelopment of maps that document localseismic hazard information;Develop budgetand cost estimatePre-plan field survey andidentify the area to bescreened2.1 Screening ImplementationSequenceThere are several steps involved inplanning and performing an RVS ofpotentially seismically hazardous buildings.As a first step, if it is to be a public orcommunity project, the local governingbody and local building officials shouldformally approve of the general procedure.Second, the public or the members of thecommunity should be informed about thepurpose of the screening process and how itwill be carried out. There are also otherdecisions to be made, such as use of thescreening results, responsibilities of thebuilding owners and the community, andactions to be taken. Some of thesedecisions are specific to each communityand therefore are not discussed in thisHandbook.The general sequence of implementingthe RVS procedure is depicted in Figure2-1. The implementation sequenceincludes:• Budget development and costestimation, recognizing the expectedextent of the screening and further useof the gathered data;• Pre-field planning, including selectionof the area to be surveyed,identification of building types to beChoose your screeners, trainthem and make assignmentsAcquire and reviewpre-field data,including existingbuilding files,databases, and soiltypes for thesurveyed areaIf you have accessto the interior, verifyconstruction typeand planirregularitiesPhotograph the building withinstant or digital cameraReview existingconstructiondrawings, ifavailable to verifyage, size,construction type,and irregularitiesCheck forquality andfile the fielddata in therecord keepingsystemSelect and reviewData CollectionFormScreen the buildingfrom the exterior onall available sides;sketch the plan andelevationFigure 2-1 Rapid visual screening implementation sequence.FEMA 154 2: Planning and Managing Rapid Visual Screening 5

• Selection and review of the Data CollectionForm;• Selection and training of screening personnel;• Acquisition and review of pre-field data;including review of existing building files anddatabases to document information identifyingbuildings to be screened (e.g., address, lotnumber, number of stories, design date) andidentifying soil types for the survey area;• Review of existing building plans, if available;• Field screening of individual buildings (seeChapter 3 for details), which consists of:1. Verifying and updating buildingidentification information,2. Walking around the building andsketching a plan and elevation view on theData Collection Form,3. Determining occupancy (that is, thebuilding use and number of occupants),4. Determining soil type, if not identifiedduring the pre-planning process,5. Identifying potential nonstructural fallinghazards,6. Identifying the seismic-lateral-loadresistingsystem (entering the building, ifpossible, to facilitate this process) andcircling the Basic Structural Hazard Scoreon the Data Collection Form,7. Identifying and circling the appropriateseismic performance attribute ScoreModifiers (e.g., number of stories, designdate, and soil type) on the Data CollectionForm,8. Determining the Final Score, S (byadjusting the Basic Structural HazardScore with the Score Modifiers identifiedin Step 7), and deciding if a detailedevaluation is required, and9. Photographing the building; and• Checking the quality and filing the screeningdata in the record-keeping system, or database.2.2 Budget Development and CostEstimationMany of the decisions that are made about thelevel of detail documented during the rapid visualscreening procedure will depend upon budgetconstraints. Although the RVS procedure isdesigned so field screening of each buildingshould take no more than 15 to 30 minutes (30minutes to one hour if access to the interior isobtained), time and funds should also be allocatedfor pre-field data collection. Pre-field datacollection can be time consuming (10 to 30minutes per building depending on the type ofsupplemental data available). However, it can beextremely useful in reducing the total field timeand can increase the reliability of data collected inthe field. A good example of this is the age, ordesign date, of a building. This might be readilyavailable from building department files but ismuch more difficult to estimate from the street.Another issue to consider is travel time, if thedistance between buildings to be screened is large.Because pre-field data collection and travel timecould be a significant factor in budget allocations,it should be considered in the planning phase.Other factors that should be considered in costestimation are training of personnel and thedevelopment and administration of a recordkeepingsystem for the screening process. Thetype of record keeping system selected will be afunction of existing procedures and availablefunds as well as the ultimate goal of the screening.For example, if the screening is to be used solelyfor potential seismic damage estimation purposes,administrative costs will be different from those ofa screening in which owners of low-scoringbuildings must subsequently be notified, andcompliance with ordinances is required.2.3 Pre-Field PlanningThe RVS authority may decide due to budget, timeor other types of constraints, that priorities shouldbe set and certain areas within the region shouldbe surveyed immediately, whereas other areas canbe surveyed at a later time because they areassumed to be less hazardous. An area may beselected because it is older and may have a higherdensity of potentially seismically hazardousbuildings relative to other areas. For example anolder part of the RVS authority region that consistsmainly of commercial unreinforced masonrybuildings may be of higher priority than a newerarea with mostly warehouse facilities, or aresidential section of a city consisting of woodframesingle-family dwellings.Compiling and developing maps for thesurveyed region is important in the initial planningphase as well as in scheduling of screeners. Mapsof soil profiles, although limited, will be directlyuseful in the screening, and maps of landslidepotential, liquefaction potential, and active faults6 2: Planning and Managing Rapid Visual Screening FEMA 154

provide useful background information about therelative hazard in different areas. Maps of lotswill be useful in scheduling screeners and, as dataare collected, in identifying areas with largenumbers of potentially hazardous buildings.Another important phase of pre-field planningis interaction with the local design profession andbuilding officials. Discussions should includeverification of when certain aspects of seismicdesign and detailing were adopted and enforced.This will be used in adjusting the scoring systemfor local practices and specifying benchmarkyears.The record-keeping system will vary amongRVS authorities, depending on needs, goals,budgets and other constraints, and may in factconsist of several systems. Part of this planningphase may include deciding how buildings are tobe identified. Some suggestions are street address,assessor’s parcel number, census tract, and lotnumber or owner. Consideration should be givento developing a computerized database containinglocation and other building information, whichcould easily be used to generate peel-off labelsfor the Data Collection Form, or to generateforms that incorporate unique information foreach building.The advantage of using a computerizedrecord generation and collection system is thatgraphical data, such as sketches andphotographs, are increasingly more easilyconverted to digital form and stored on thecomputer, especially if they are collected indigital format in the field. This can befacilitated through the use of personal digitalassistants (PDAs), which would require thedevelopment of a FEMA 154 application, andthe use of digital cameras.If a computerized database is not used,microfilm is a good storage medium fororiginal hard copy, because photographs,building plans, screening forms and subsequentfollow-up documentation can be kept togetherand easily copied. Another method that hasbeen used is to generate a separate hard-copyfile for each building as it is screened. In fact,the screening form can be reproduced on alarge envelope and all supporting material andphotographs stored inside. This solves anyproblems associated with attaching multiplesketches and photographs, but the files growrapidly and may become unmanageable.2.4 Selection and Review of theData Collection FormThere are three Data Collection Forms, one foreach of the following three regions of seismicity:low (L), moderate (M), and high (H). Full-sizedversions of each form are provided in Appendix B,along with a Quick Reference Guide that containsdefinitions and explanations for terms used on theData Collection Form. Each Data Collection Form(see example, Figure 2-2) provides space torecord the building identification information,draw a sketch of the building (plan andelevation views), attach a photograph of thebuilding, indicate the occupancy, indicate the soiltype, document the existence of falling hazards,develop a Final Structural Score, S, for thebuilding, indicate if a detailed evaluation isrequired, and provide additional comments. Thestructural scoring system consists of a matrix ofBasic Structural Hazard Scores (one for eachbuilding type and its associated seismic lateralforce-resistingsystem) and Score Modifiers toFigure 2-2Example RVS Data Collection Form (highseismicity).FEMA 154 2: Planning and Managing Rapid Visual Screening 7

account for observed attributes that modifyseismic performance. The Basic Structural HazardScores and Score Modifiers are based on (1)design and construction practices in the region, (2)attributes known to decrease or increase seismicresistance capacity, and (3) maximum consideredground motions for the seismicity region underconsideration. The Basic Structural Hazard Score,Score Modifiers, and Final Structural Score, S, allrelate to the probability of building collapse,should the maximum ground motions consideredby the RVS procedure occur at the site. Final Sscores typically range from 0 to 7, with higher Sscores corresponding to better seismicperformance.The maximum ground motions considered inthe scoring system of the RVS procedure areconsistent with those specified for detailedbuilding seismic evaluation in the FEMA 310Report, Handbook for the Seismic Evaluation ofBuildings—A Prestandard. Such ground motionsgenerally have a 2% chance of being exceeded in50 years, and are multiplied by a 2/3 factor in theFEMA 310 evaluation procedures and in thedesign requirements for new buildings in FEMA302, Recommended Provisions for SeismicRegulations for New Buildings and OtherStructures (BSSC, 1997). (Ground motions havinga 2% probability of being exceeded in 50 years arecommonly referred to as the maximum consideredearthquake (MCE) ground motions.)2.4.1 Determination of Seismicity RegionTo select the appropriate Data Collection Form,it is first necessary to determine the seismicityregion in which the area to be screened is located.The seismicity region (H, M, or L) for the screeningarea can be determined by one of two methods:1. Find the location of the surveyed region on theseismicity map of Figure 1-1, or one of theenlarged seismicity maps provided in AppendixA, and identify the corresponding seismicityregion, or;2. Access the U.S. Geological Survey web page(http://geohazards.cr.usgs.gov/eq/), select“Hazard by Zip Code” or “Hazard by Lat/Long”under the “Seismic Hazard” heading, enter theappropriate values of zip code or latitude andlongitude, select the spectral acceleration value(SA) for a period of 0.2 seconds and the SAvalue for a period of 1.0 second, multiply the SAvalues by 2/3, and use the criteria of Table 2-1 toselect the appropriate seismicity region,assuming that the highest seismicity leveldefined by the parameters in Table 2-1 shallgovern.Use more recent additions of these maps whenthey become available.The web site approach of Method 2, which usesseismicity region definitions used in other recentlydeveloped FEMA documents, is preferred as itenables the user to determine seismicity based on amore precisely specified location. In contrast, eachcounty shown in Figure 1-1 is assigned its seismicityon the basis of the highest seismicity in that county,even though it may only apply to a small portion ofthe county.Table 2-1Region ofSeismicityLowModerateRegions of Seismicity withCorresponding Spectral AccelerationResponse (from FEMA 310)Spectral AccelerationResponse, SA (shortperiod,or 0.2 sec)less than 0.167 g (inhorizontal direction)greater than or equalto 0.167 g but lessthan 0.500 g (inhorizontal direction)High greater than or equalto 0.500 g (inhorizontal direction)Notes: g = acceleration of gravitySpectral AccelerationResponse, SA (longperiodor 1.0 sec)less than 0.067 g (inhorizontal direction)greater than or equalto 0.067 g but lessthan 0.200 g (inhorizontal direction)greater than or equalto 0.200 g (inhorizontal direction)2.4.2 Determination of Key Seismic CodeAdoption Dates and OtherConsiderationsThe Data Collection Form is meant to be amodel that may be adopted and used as it ispresented in this Handbook. The form may also bemodified according to the needs of the RVSauthority. Therefore, another aspect of thescreening planning process is to review the DataCollection Form to determine if all required dataare represented or if modifications should be madeto reflect the needs and special circumstances ofthe authority. For example, an RVS authority maychoose to define additional occupancy classes suchas “parking structure” or “multi-familyresidential.”One of the key issues that must be addressedin the planning process is the determination of (1)the year in which seismic codes were initially8 2: Planning and Managing Rapid Visual Screening FEMA 154

Table 2-2. Benchmark Years for RVS Procedure Building Types (based on FEMA 310)Model Building Seismic Design ProvisionsBuilding Type BOCA SBCC UBC NEHRPW1: Light wood-frame residential and commercial buildingssmaller than or equal to 5,000 square feet1992 1993 1976 1985W2: Light wood-frame buildings larger than 5,000 squarefeet1992 1993 1976 1985S1: Steel moment-resisting frame buildings ** ** 1994 **S2: Braced steel frame buildings 1992 1993 1988 1991S3: Light metal buildings * * * *S4: Steel frame buildings with cast-in-place concrete shearwalls1992 1993 1976 1985S5: Steel frame buildings with unreinforced masonry infillwalls* * * *C1: Concrete moment-resisting frame buildings 1992 1993 1976 1985C2: Concrete shear-wall buildings 1992 1993 1976 1985C3: Concrete frame buildings with unreinforced masonryinfill walls* * * *PC1: Tilt-up buildings * * 1997 *PC2: Precast concrete frame buildings * * * *RM1: Reinforced masonry buildings with flexible floor androof diaphragms* * 1997 *RM2: Reinforced masonry buildings with rigid floor and roofdiaphragms1992 1993 1976 1985URM: Unreinforced masonry bearing-wall buildings * * 1991 **No benchmark year; **contact local building department for benchmark year.BOCA: Building Officials and Code Administrators, National Building CodeSBCC: Southern Building Code Congress, Standard Building Code.UBC: International Conference of Building Officials, Uniform Building CodeNEHRP: National Earthquake Hazard Reduction Program, FEMA 302 Recommended Provisions for the Development of SeismicRegulations for New Buildingsadopted and enforced by the local jurisdiction, and(2) the year in which significantly improvedseismic codes were adopted and enforced (thislatter year is known as the benchmark year). Inhigh and moderate seismicity regions, the BasicStructural Hazard Scores for the various buildingtypes are calculated for buildings built after theinitial adoption of seismic codes, but beforesubstantially improved codes were adopted. Forthese regions, Score Modifiers designated as “PreCode” and “Post Benchmark” are provided,respectively, for buildings built before theadoption of codes and for buildings built after theadoption of substantially improved codes. In lowseismicity regions, the Basic Structural HazardScores are calculated for buildings built before theinitial adoption of seismic codes. For buildings inthese regions, the Score Modifier designated as“Pre Code” is not applicable (N/A), and the ScoreModifier designated as “Post Benchmark” isapplicable for buildings built after the adoption ofseismic codes.Therefore, as part of this review process, theRVS authority should identify (1) the year inwhich seismic codes were first adopted andenforced in the area to be screened, (2) the“benchmark” year in which significantly improvedseismic code requirements were adopted for eachbuilding type considered by the RVS procedure(see Table 2-2), and (3) the year in which thecommunity adopted seismic anchoragerequirements for heavy cladding. If the RVSauthority in high and moderate seismicity regionsis unsure of the year(s) in which codes wereinitially adopted, the default year for all but onebuilding type is 1941 (the default year specified inthe HAZUS criteria; NIBS, 1999). The oneexception is PC1 (tilt-up) buildings, for which it isassumed that seismic codes were initially adoptedin 1973, the year in which wall-diaphragm (ledger)connection requirements first appeared in theUniform Building Code (ICBO, 1973).During the review of the Data CollectionForm, the RVS authority should confer with theFEMA 154 2: Planning and Managing Rapid Visual Screening 9

1. Model Building Types and Critical Code Adoptionand Enforcement Dates Year Seismic Codes BenchmarkInitially Adopted Year WhenStructure Types and Enforced* Codes ImprovedW1 Light wood frame, residential or commercial, < 5000 square feet _______ _______W2 Wood frame buildings, > 5000 square feet _______ _______S1 Steel moment-resisting frame _______ _______S2 Steel braced frame _______ _______S3 Light metal frame _______ _______S4 Steel frame with cast-in-place concrete shear walls _______ _______S5 Steel frame with unreinforced masonry infill _______ _______C1 Concrete moment-resisting frame _______ _______C2 Concrete shear wall _______ _______C3 Concrete frame with unreinforced masonry infill _______ _______PC1 Tilt-up construction _______ _______PC2 Precast concrete frame _______ _______RM1 Reinforced masonry with flexible floor and roof diaphragms _______ _______RM2 Reinforced masonry with rigid diaphragms _______ _______URM Unreinforced masonry bearing-wall buildings _______ _______*Not applicable in regions of low seismicity2. Anchorage of Heavy CladdingYear in which seismic anchorage requirements were adopted:_______Figure 2-3 Sections 1 and 2 of Quick Reference Guide (for use with Data Collection Form).chief building official, plan checkers, and otherdesign professionals experienced in seismic designto identify the years in which the affectedjurisdiction initially adopted and enforced seismiccodes (if ever) for the building lateral-forceresistingstructural systems considered by the RVSprocedure. Since municipal codes are generallyadopted by the city council, another source for thisinformation, in many municipalities, is the cityclerk’s office. In addition to determining the yearin which seismic codes were initially adopted andenforced, the RVS authority should also determine(1) the benchmark years in which substantiallyimproved seismic codes were adopted andenforced for the various lateral-load-resistingsystems and (2) the year in which anchoragerequirements for cladding were adopted andenforced. These dates should be inserted on theQuick Reference Guide (Appendix B) that hasbeen created to facilitate the use of the DataCollection Form (see Figure 2-3).During the Data Collection Form reviewprocess, it is critically important that the BasicStructural Hazard Scores and Score Modifiers,which are described in detail in Chapter 3, not bechanged without input from professional engineersfamiliar with earthquake-resistant design andconstruction practices of the local community. Achecklist of issues to be considered whenreviewing the Data Collection Form is provided inTable 2-3.Table 2-3 Checklist of Issues to be ConsideredDuring Pre-Field Work Review of theData Collection FormEvaluate completeness of occupancy categoriesand appropriateness of occupancy loadsDetermine year in which seismic codes wereinitially adopted in the jurisdictionDetermine “benchmark” years in which thejurisdiction adopted and enforced significantlyimproved seismic codes for the various buildingtypes considered by the RVS procedureDetermine year in which the jurisdictionadopted and enforced anchorage requirementsfor heavy cladding2.4.3 Determination of Cut-Off ScoreUse of the RVS on a community-wide basisenables the RVS authority to divide screenedbuildings into two categories: those that areexpected to have acceptable seismic performance,and those that may be seismically hazardous and10 2: Planning and Managing Rapid Visual Screening FEMA 154

should be studied further. This requires that theRVS authority determine, preferably as part of thepre-planning process, an appropriate “cut-off”score.An S score of 2 is suggested as a “cut-off”,based on present seismic design criteria. Usingthis cut-off level, buildings having an S score of 2or less should be investigated by a designprofessional experienced in seismic design (seeSection 3.9, 4.1 and 4.2 for additional informationon this issue).2.5 Qualifications and Training forScreenersIt is anticipated that a training program will berequired to ensure a consistent, high quality of thedata and uniformity of decisions among screeners.Training should include discussions of lateralforce-resistingsystems and how they behave whensubjected to seismic loads, hw to use the DataCollection Form, what to look for in the field, andhow to account for uncertainty. In conjunctionwith a professional engineer experienced inseismic design, screeners should simultaneouslyconsider and score buildings of several differenttypes and compare results. This will serve as a“calibration” for the screeners.This process can easily be accomplished in aclassroom setting with photographs of actualbuildings to use as examples. Prospectivescreeners review the photographs and perform theRVS procedure as though they were on thesidewalk. Upon completion, the class discussesthe results and students can compare how they didin relation to the rest of the class.2.6 Acquisition and Review of Pre-Field DataInformation on the structural system, age oroccupancy (that is, use) may be available fromsupplemental sources. These data, from assessorand building department files, insurance (Sanborn)maps, and previous studies, should be reviewedand collated for a given area before commencingthe field survey for that area. It is recommendedthat this supplemental information either bewritten directly on the Data Collection Forms as itis retrieved or be entered into a computerizeddatabase. The advantage of a database is thatselected information can be printed in a reportformat that can be taken into the field, or printedonto peel-off labels that can be affixed to the DataCollection Form (see Figure 2-4). In addition,screening data can be added to the databases andFigure 2-4 Building identification portion of RVSData Collection Form.used to generate maps and reports. Some sourcesof supplemental information are described inSections 2.6.1 through 2.6.5.2.6.1 Assessor’s FilesAlthough assessor’s files may contain informationabout the age of the building, the floor area andthe number of stories, most information relates toownership and assessed value of the land andimprovements, and thus is of relatively little valuefor RVS purposes. The construction typeindicated is often incorrect and in most casesshould not be used. In addition, the age of abuilding retrieved from assessor’s files may not,and most likely is not, the year that the structurewas built. Usually assessor’s files contain the yearthat the building was first eligible for taxation.Because the criteria for this may vary, the datemay be several years after the building wasdesigned or constructed. If no other source ofinformation is available this will give a goodestimate of the period during which the buildingFEMA 154 2: Planning and Managing Rapid Visual Screening 11

was constructed. However, this date should not beused to establish conclusively the code underwhich the a building was designed. Assessor’soffices may have parcel or lot maps, which may beuseful for locating sites or may be used as atemplate for sketching building adjacencies on aparticular city block.2.6.2 Building Department FilesThe extent and completeness of information inbuilding department files will vary fromjurisdiction to jurisdiction. For example, in somelocations all old files have been removed ordestroyed, so there is no information on olderbuildings. In general, files (or microfilm) maycontain permits, plans and structural calculationsrequired by the city.Sometimes there isoccupancy and useinformation, but littleinformation aboutstructural type will befound except from thereview of plans orcalculations.Information found on a Sanborn map includes:• height of building,• number of stories,• year built,• thickness of walls,• building size (square feet),• type of roof (tile, shingle, composite),• building use (dwelling, store, apartment),• presence of garage under structure, and• structural type (wood frame, fireproofconstruction, adobe, stone, concrete).2.6.3 Sanborn MapsThese maps, publishedprimarily for theinsurance industry sincethe late 1800s, exist forabout 22,000communities in theUnited States. TheSanborn Map Companystopped routinelyupdating these maps inthe early 1960s, and manycommunities have notkept these maps up-todate.Thus they may notbe useful for newerconstruction. However,the maps may containuseful data for olderconstruction. They can befound at the library or insome cases in buildingdepartment offices. Figure2-5 provides an exampleof an up-to-date Sanbornmap Figure 2-6 shows akey to identifiers onSanborn maps.Figure 2-5Example Sanborn map showing building information for a city block.12 2: Planning and Managing Rapid Visual Screening FEMA 154

Figure 2-6Key to Sanborn map symbols. Also, see the Internet, www.sanbornmap.com.Parcel maps are also available and contain lotdimensions. If building size information cannot beobtained from another source such as theassessor’s file, the parcel maps are particularlyhelpful for determining building dimensions inurban areas where buildings cover the entire lot.However, even if the building does not cover theentire lot, it will be easier to estimate buildingdimensions if the lot dimensions are known.Figures 2-7 and 2-8 show a Sanborn map andphotographs of a city block. Building descriptionsobtained from the Sanborn maps are also included.FEMA 154 2: Planning and Managing Rapid Visual Screening 13

1. 10 story commercial office2. 3 story commercial, built 19133. 2 story commercial4. 3 story commercial, reinforced concrete frame, built 19065. 7 story commercial office, reinforced concrete frame, built 19236. 2 story commercial, reinforced concrete7. 5 story commercial office, reinforced concrete8. 20 story commercial office, steel frame with reinforced concrete, built 19149. 4 story commercial, built 196610. 40 story commercial office, built 1965-66, concrete and glass exteriorFigure 2-7Sanborn map and corresponding aerial photograph of a city block.14 2: Planning and Managing Rapid Visual Screening FEMA 154

Although the information onSanborn maps may be useful,it is the responsibility of thescreener to verify it in thefield.2.6.4 MunicipalDatabasesWith the widespread use ofthe internet, manyjurisdictions are creating “online”electronic databases foruse by the general public.These databases providegeneral information on thevarious building sites withinthe jurisdiction. Thesedatabases are not detailedenough at this point in time toprovide specific informationabout the buildings; they do,however, provide some gooddemographic information thatcould be of use. As themunicipalities develop morecomprehensive information,these databases will becomemore useful to the RVSscreening. Figure 2-9 showsexamples of the databasesfrom two municipalities in theUnited States.2.6.5 Previous StudiesIn a few cases, previousbuilding inventories or studiesof hazardous buildings orhazardous nonstructuralelements (e.g.,parapets) may have beenperformed. These studies may be limited to aparticular structural or occupancy class, but theymay contain useful maps or other relevantstructural information and should be reviewed.Other important studies might address relatedseismic hazard issues such as liquefaction orlandslide potential. Local historical societies mayhave published books or reports about olderbuildings in the community. Fire departments areoften aware of the overall condition andcomposition of building interiors.Figure 2-8 Photographs of elevation views of buildings shown in Figure 2-7.2.6.6 Soils InformationSoil type has a major influence on amplitude andduration of shaking, and thus structural damage.Generally speaking, the deeper the soils at a site, themore damaging the earthquake motion will be. Thesix soil types considered in the RVS procedure arethe same as those specified in the FEMA 302 report,NEHRP Recommended Provisions for the SeismicDesign of New Buildings and Other Structures(BSSC, 1997): hard rock (type A); average rock(type B); dense soil (type C), stiff soil (type D); softsoil (type E), and poor soil (type F). Additionalinformation on these soil types and how to identifyFEMA 154 2: Planning and Managing Rapid Visual Screening 15

City of Oakland, CaliforniaMecklenburg County, North CarolinaFigure 2-9Examples of in-house screen displays of municipal databases.16 2: Planning and Managing Rapid Visual Screening FEMA 154

Figure 2-10 Location on Data Collection Formwhere soil type information isrecorded.them are provided in the side bar. Buildings onsoil type F cannot be screened effectively by theRVS procedure, other than to recommend thatbuildings on this soil type be further evaluated bya geotechnical engineer and design professionalexperienced in seismic design.Since soil conditions cannot be readilyidentified by visual methods in the field, geologicand geotechnical maps and other informationshould be collected during the planning stage andput into a readily usable map format for use duringRVS. During the screening, or the planning stage,this soil type should also be documented on theData Collection Form by circling the correct soiltype, as designated by the letters A through F, (seeFigure 2-10). If sufficient guidance or data are notavailable during the planning stage to classify thesoil type as A through E, a soil type E should beassumed. However, for one-story or two-storybuildings with a roof height equal to or less than25 feet, a class D soil type may be assumed whensite conditions are not known. (See the note inpreceding paragraph regarding soil type F.)2.7 Review of ConstructionDocumentsWhenever possible, design and constructiondocuments should be reviewed prior to theSoil Type Definitions and Related ParametersThe six soil types, with measurable parameters thatdefine each type, are:Type A (hard rock): measured shear wave velocity, v s> 5000 ft/sec.Type B (rock): v s between 2500 and 5000 ft/sec.Type C (soft rock and very dense soil): v s between1200 and 2500 ft/sec, or standard blow count N > 50, orundrained shear strength s u > 2000 psf.Type D (stiff soil): v s between 600 and 1200 ft/sec, orstandard blow count N between 15 and 50, or undrainedshear strength, s u between 1000 and 2000 psf.Type E (soft soil): More than 100 feet of soft soil withplasticity index PI > 20, water content w > 40%, ands u < 500 psf; or a soil with v s ≤ 600 ft/sec.Type F (poor soil): Soils requiring site-specificevaluations:• Soils vulnerable to potential failure or collapseunder seismic loading, such as liquefiable soils,quick and highly-sensitive clays, collapsibleweakly-cemented soils.• Peats or highly organic clays (H > 10 feet of peator highly organic clay, where H = thickness ofsoil.).• Very high plasticity clays (H > 25 feet withPI > 75).• More than 120 ft of soft or medium stiff clays.The parameters v s , N, and s u are, respectively, theaverage values (often shown with a bar above) of shearwave velocity, Standard Penetration Test (SPT) blowcount and undrained shear strength of the upper 100feet of soils at the site.conduct of field work to help the screener identifythe type of lateral-force- resisting system for eachbuilding. The review of construction documentsto identify the building type substantially improvesthe confidence in this determination. As describedin Section 3.7, the RVS procedure requires thateach building be identified as one of 15 modelbuilding types 2 . Guidance for reviewing designand construction drawings is provided inAppendix C.2 The 15 model building types used in FEMA 154 are anabbreviated list of the 22 types now considered standardby FEMA; excluded from the FEMA 154 list are subclassificationsof certain framing types that specify thatthe roof and floor diaphragms are either rigid orflexible.FEMA 154 2: Planning and Managing Rapid Visual Screening 17

2.8 Field Screening of BuildingsRVS screening of buildings in the field should becarried out by teams consisting of two individuals.Teams of two are recommended to provide anopportunity to discuss issues requiring judgmentand to facilitate the data collection process. If atall possible, one of the team members should be adesign professional who can identify lateral-forceresistingsystems.Relatively few tools or equipment are needed.Table 2-4 contains a checklist of items that may beneeded in performing an RVS as described in thisHandbook.2.9 Checking the Quality and Filingthe Field Data in the Record-Keeping SystemThe last step in the implementation of rapid visualscreening is checking the quality and filing theRVS data in the record-keeping system establishedfor this purpose. If the data are to be stored in filefolders or envelopes containing data for eachbuilding that was screened, or on microfilm, theprocess is straightforward, and requires carefulorganization. If the data are to be stored in digitalform, it is important that the data input andverification process include either double entry ofall data, or systematic in-depth review of print outs(item by item review) of all entered data.It is also recommended that the quality reviewbe performed under the oversight of a designprofessional with significant experience in seismicdesign.Table 2-4Checklist of Field EquipmentNeeded for Rapid Visual ScreeningBinoculars, if high-rise buildings are to beevaluatedCamera, preferably instant or digitalClipboard for holding Data Collection FormsCopy of the FEMA 154 HandbookLaminated version of the Quick Reference Guidedefining terms used on the Data Collection Form(see Appendix B)Pen or pencilStraight edge (optional for drawing sketches)Tape or stapler, for affixing photo if instantcamera is used18 2: Planning and Managing Rapid Visual Screening FEMA 154

Chapter 3Completing theData Collection Form3.1 IntroductionThis chapter provides instructions on how tocomplete the Data Collection Form (Figure3-1). It is assumed that the Data CollectionForm has already been selected, based on theseismicity level of the area to be screened (asper Chapter 2). The Data Collection Form iscompleted for each building screened throughexecution of the following steps:1. Verifying and updating the buildingidentification information;2. Walking around the building to identify itssize and shape, and sketching a plan andelevation view on the Data CollectionForm;3. Determining and documenting occupancy;4. Determining soil type, if not identifiedduring the pre-planning process;5. Identifying potential nonstructural fallinghazards, if any, and indicating theirexistence on the Data Collection Form;6. Identifying the seismic lateral-loadresisting system (entering the building, ifpossible, to facilitate this process) andcircling the related Basic Structural HazardScore on the Data Collection Form;7. Identifying and circling the appropriateseismic performance attribute ScoreFigure 3-1 Example RVS Data Collection Form (high seismicity).Modifiers (e.g., number of stories, designdate, and soil type) on the Data Collectionused), or indicating a photo reference numberForm;on the form (if a digital camera is used).8. Determining the Final Score, S (by adjustingFull-sized copies of the Data Collection Formsthe Basic Structural Hazard Score with the(one for each seismicity region) are provided inScore Modifiers identified in Step 7), andAppendix B, along with a Quick Reference Guidedeciding if a detailed evaluation is required; defining terms used on the Data Collection Form.andThe form has been designed to be filled out in aprogressive manner, with a minimum of writing9. Photographing the building and attaching the(most items simply can be circled).photo to the form (if an instant camera isFollowing are detailed instructions andguidance for each of the nine steps above.FEMA 154 3: Completing the Data Collection Form 19

3.2 Verifying and Updating theBuilding IdentificationInformationSpace is provided in the upper right-hand portionof the Data Collection Form (see Figure 3-2) todocument building identification information (i.e.,address, name, number of stories, year built, andother data). As indicated in Chapter 2, it isdesirable to develop and document thisinformation during the pre-planning stage, if at allpossible. This information may be enteredmanually, or be printed on a peel-off label.Proper identification and location of thebuilding is critically important for subsequent usein hazard assessment and mitigation by the RVSauthority. As described in Chapter 2, the authoritymay prefer to identify and file structures by streetaddress, parcel number, building owner, or someother scheme. However, it is recommended that asa minimum the street address and zip code berecorded on the form. Zip code is importantbecause it is universal to all municipalities, is anespecially useful item for later collation andsummary analyses. Assessor parcel number or lotnumber is also useful for jurisdictional recordkeepingpurposes.Assuming the identification information isprovided on a peel-off label, which is then affixedto the form, or preprinted directly on the form,such information should be verified in the field. Ifthe building identification data are not developedduring the pre-planning stage, it must becompleted in the field. Documentation of thebuilding address information and name, if it exists,is straightforward. Following is guidance anddiscussion pertaining to number of stories, yearbuilt, identification of the screener, and estimationof total floor area.3.2.1 Number of StoriesThe height of a structure is sometimes related tothe amount of damage it may sustain. On softsoils, a tall building may experience considerablystronger and longer duration shaking than a shorterbuilding of the same type. The number of storiesis a good indicator of the height of a building(approximately 9-to-10 feet per story forresidential, 12 feet per story for commercial oroffice).Counting the number of stories may not be astraightforward issue if the building is constructedon a hill or if it has several different roof levels.As a general rule, use the largest number (that is,Figure 3-2 Portion of Data Collection Form fordocumenting buildingidentification.count floors from the downhill side to the roof).In addition, the number of stories may not beunique. A building may be stepped or have atower. Use the comment section and the sketch toindicate variations in the number of stories.3.2.2 Year BuiltThis information is one of the key elements of theRVS procedure. Building age is tied directly todesign and construction practices. Therefore, agecan be a factor in determining building type andthus can affect the final scores. This informationis not typically available at the site and thus shouldbe included in pre-field data collection.There may be no single “year built.” Certainportions of the structure may have been designedand constructed before others. If this should bethe case, the construction dates for each portioncan be indicated in the comment section or on thesketch (see Section 3.3). Caution should also beused when interpreting design practices from dateof construction. The building may have beendesigned several years before it was constructedand thus designed to an earlier code with differentrequirements for seismic detailing.If information on “year built” is not availableduring the RVS pre-field data acquisition stage(see Section 2.6), a rough estimate of age will bemade on the basis of architectural style andbuilding use. This is discussed in more detail inAppendix D, which provides additional guidanceon determining building attributes from streetside.If the year built is only an approximation, anasterisk is used to indicate the entry is estimated.3.2.3 Screener IdentificationThe screener should be identified, by name,initials, or some other type of code. At some latertime it may be important to know who the screenerwas for a particular building, so this informationshould not be omitted.20 3: Completing the Data Collection Form FEMA 154

Figure 3-3SKETCHESSample Data Collection Formshowing location for sketches ofbuilding plan and elevation views.made. In other words, it forces the screener tosystematically view all aspects of the building.The plan sketch should include the location of thebuilding on the site and distance to adjacentbuildings. One suggestion is to make the plansketch from a Sanborn map as part of pre-fieldwork (see Chapter 2), and then verify it in thefield. This is especially valuable when accessbetween buildings is not available. If all sides ofthe building are different, an elevation should besketched for each side. Otherwise indicate that thesketch is typical of all sides. The sketch shouldnote and emphasize special features such asexisting significant cracks or configurationproblems.Dimensions should be included. As indicatedin the previous section, the length and width of thebuilding can be paced off or estimated (during theplanning stage) from Sanborn or other parcelmaps.3.4 Determining Soil TypeAs indicated in Section 2.6.6, soil type should beidentified and documented on the Data CollectionForm (see Figure 3-4) during the pre-field soilsdata acquisition and review phase. If soil type hasnot been determined as part of that process, itneeds to be identified by the screener during the3.2.4 Total Floor AreaThe total floor area, in some cases available frombuilding department or assessor files (see Section2.6), will most likely be estimated by multiplyingthe estimated area of one story by the total numberof stories in the building. The length and width ofthe building can be paced off or estimated (duringthe planning stage) from Sanborn or other parcelmaps. Total floor area is useful for estimatingoccupancy load (see Section 3.5.2) and may beuseful at a later time for estimating the value of thebuilding. Indicate with an asterisk when totalfloor area is estimated.3.3 Sketching the Plan andElevation ViewsAs a minimum, a sketch of the plan of the buildingshould be drawn on the Data Collection Form (seeFigure 3-3). An elevation may also be useful inindicating significant features. The sketches areespecially important, as they reveal many of thebuilding’s attributes to the screener as the sketch isFigure 3-4Location on Data Collection Formwhere soil type information isdocumented (circled).FEMA 154 3: Completing the Data Collection Form 21

uilding site visit. If there is no basis forclassifying the soil type, a soil type E should beassumed. However, for one-story or two-storybuildings with a roof height equal to or less than25 feet, a class D soil type may be assumed whensite conditions are not known.3.5 Determining and DocumentingOccupancyTwo sets of information are needed relative tooccupancy: (1) building use, and (2) estimatednumber of persons occupying the building.3.5.1 OccupancyOccupancy-related information is indicated bycircling the appropriate information in the leftcenterportion of the form (see Figure 3-5). Theoccupancy of a building refers to its use, whereasthe occupancy load is the number of people in thebuilding (see Section 3.5.2). Although usually notbearing directly on the structural hazard orprobability of sustaining major damage, theoccupancy of a building is of interest and usewhen determining priorities for mitigation.Nine general occupancy classes that are easyto recognize have been defined. They are listed onthe form as Assembly, Commercial, EmergencyServices (Emer. Services), Government (Govt),Historic, Industrial, Office, Residential, Schoolbuildings. These are the same classes used in thefirst edition of FEMA 154. They have beenretained in this edition for consistency, they areeasily identifiable from the street, they generallyrepresent the broad spectrum of building uses inthe United States, and they are similar to theoccupancy categories in the Uniform BuildingCode (ICBO, 1997).The occupancy class that best describes thebuilding being evaluated should be circled on theform. If there are several types of uses in thebuilding, such as commercial and residential, bothshould be circled. The actual use of the buildingmay be written in the upper right hand portion ofthe form. For example, one might indicate thatthe building is a post office or a library on the linetitled “use” in the upper right of the form (seeFigure 3-2). In both of these cases, one would alsocircle “Govt”. If none of the defined classes seemto fit the building, indicate the use in the upperright portion of the form (the buildingidentification area) or include an explanation inthe comments section. The nine occupancyclasses are described below (with generalindications of occupancy load):• Assembly. Places of public assembly are thosewhere 300 or more people might be gatheredin one room at the same time. Examples aretheaters, auditoriums, community centers,performance halls, and churches. (Occupancyload varies greatly and can be as much as 1person per 10 sq. ft. of floor area, dependingprimarily on the condition of the seating—fixed versus moveable).• Commercial. The commercial occupancyclass refers to retail and wholesale businesses,financial institutions, restaurants, parkingstructures and light warehouses. (Occupancyload varies; use 1 person per 50 to 200 sq. ft.).• Emergency Services. The emergency servicesclass is defined as any facility that wouldlikely be needed in a major catastrophe. Theseinclude police and fire stations, hospitals, andcommunications centers. (Occupancy load istypically 1 person per 100 sq. ft.).• Government. This class includes local, stateand federal non-emergency related buildings(Occupancy load varies; use 1 person per 100to 200 sq. ft.).• Historic. This class will vary from communityto community. It is included because historicbuildings may be subjected to specificordinances and codes.22 3: Completing the Data Collection Form FEMA 154

• Industrial. Included in the industrialoccupancy class are factories, assembly plants,large warehouses and heavy manufacturingfacilities. (Typically, use 1 person per 200 sq.ft. except warehouses, which are perhaps 1person per 500 sq. ft.).• Office. Typical office buildings house clericaland management occupancies (use 1 personper 100 to 200 sq. ft.).• Residential. This occupancy class refers toresidential buildings such as houses,townhouses, dormitories, motels, hotels,apartments and condominiums, and residencesfor the aged or disabled. (The number ofpersons for residential occupancies variesfrom about 1 person per 300 sq. ft. of floorarea in dwellings, to perhaps 1 person per 200sq. ft. in hotels and apartments, to 1 per 100sq. ft. in dormitories).• School. This occupancy class includes allpublic and private educational facilities fromnursery school to university level.(Occupancy load varies; use 1 person per 50 to100 sq. ft.).When occupancy is used by a community as abasis for setting priorities for hazard mitigationpurposes, the upgrade of emergency servicesbuildings is often of highest priority. Somecommunities may have special design criteriagoverning buildings for emergency services. Thisinformation may be used to add a special ScoreModifier to increase the score for speciallydesigned emergency buildings.3.6 Identifying PotentialNonstructural Falling HazardsNonstructural falling hazards such as chimneys,parapets, cornices, veneers, overhangs and heavycladding can pose life-safety hazards if notadequately anchored to the building. Althoughthese hazards may be present, the basic lateralloadsystem for the building may be adequate andrequire no further review. A series of four boxeshave been included to indicate the presence ofnonstructural falling hazards (see Figure 3-6). Thefalling hazards of major concern are:• Unreinforced Chimneys. Unreinforcedmasonry chimneys are common in oldermasonry and wood-frame dwellings. They areoften inadequately tied to the house and fallwhen strongly shaken. If in doubt as towhether a chimney is reinforced orunreinforced, assume it is unreinforced.• Parapets. Unbraced parapets are difficult toidentify from the street as it is sometimesdifficult to tell if a facade projects above theroofline. Parapets often exist on three sides ofthe building, and their height may be visiblefrom the back of the structure.• Heavy Cladding. Large heavy claddingelements, usually precast concrete or cut3.5.2 Occupancy LoadLike the occupancy class or use of the building,the occupancy load may be used by an RVSauthority in setting priorities for hazard mitigationplans. The community may wish to upgradebuildings with more occupants first. As can beseen from the form (Figure 3-5), the occupancyload is defined in ranges such as 1-10, 11-100,101-1000, and 1000+ occupants. The range thatbest describes the average occupancy of thebuilding is circled. For example, if an officebuilding appears to have a daytime occupancy of200 persons, and an occupancy of only one or twopersons otherwise, the maximum occupancy loadis 101-1000 persons. If the occupancy load isestimated from building size and use, an insertedasterisk will automatically indicate that these areapproximate data.Figure 3-6Portion of Data Collection Form fordocumenting nonstructural fallinghazards.FEMA 154 3: Completing the Data Collection Form 23

stone, may fall off the building during anearthquake if improperly anchored. The lossof panels may also create major changes to thebuilding stiffness (the elements are considerednonstructural but often contribute substantialstiffness to a building), thus setting up planirregularities or torsion when only some fall.(Glass curtain walls are not considered asheavy cladding in the RVS procedure.) Theexistence of heavy cladding is of concern ifthe connections were designed and installedbefore the jurisdiction adopted seismicanchorage requirements (normally twice thatfor gravity loads). The date of such codeadoption will vary with jurisdiction and shouldbe established by an experienced designprofessional in the planning stages of the RVSprocess (see Section 2.4.2).If any of the above nonstructural fallinghazards exist, the appropriate box should bechecked. If there are any other falling hazards, the“Other” box should be checked, and the type ofhazard indicated on the line beneath this box. Usethe comments section if additional space isrequired.The RVS authority may later use thisinformation as a basis for notifying the owner ofpotential problems.3.7 Identifying the Lateral-Load-Resisting System andDocumenting the Related BasicStructural ScoreThe RVS procedure is based on the premise thatthe screener will be able to determine thebuilding’s lateral-load-resisting system from thestreet, or to eliminate all those that it cannotpossibly be. It is further assumed that the lateralload-resistingsystem is one of fifteen types thathave been observed to be prevalent, based onstudies of building stock in the United States. Thefifteen types are consistent with the modelbuilding types identified in the FEMA 310 Reportand the predecessor documents that haveaddressed seismic evaluation of buildings (e.g.,ATC, 1987; BSSC, 1992)). The fifteen modelbuilding types used in this document, however, arean abbreviated subset of the 22 types nowconsidered standard by FEMA; excluded from theFEMA 154 list are sub-classifications of certainframing types that specify that the roof and floordiaphragms are either rigid or flexible.3.7.1 Fifteen Building Types Consideredby the RVS Procedure and RelatedBasic Structural ScoresFollowing are the fifteen building types used in theRVS procedure. Alpha-numeric reference codesused on the Data Collection Form are shown inparentheses.1. Light wood-frame residential and commercialbuildings smaller than or equal to 5,000 squarefeet (W1)2. Light wood-frame buildings larger than 5,000square feet (W2)3. Steel moment-resisting frame buildings (S1)4. Braced steel frame buildings (S2)5. Light metal buildings (S3)6. Steel frame buildings with cast-in-placeconcrete shear walls (S4)7. Steel frame buildings with unreinforcedmasonry infill walls (S5)8. Concrete moment-resisting frame buildings(C1)9. Concrete shear-wall buildings (C2)10. Concrete frame buildings with unreinforcedmasonry infill walls (C3)11. Tilt-up buildings (PC1)12. Precast concrete frame buildings (PC2)13. Reinforced masonry buildings with flexiblefloor and roof diaphragms (RM1)14. Reinforced masonry buildings with rigid floorand roof diaphragms (RM2)15. Unreinforced masonry bearing-wall buildings(URM)For each of these fifteen model building types,a Basic Structural Hazard Score has beencomputed that reflects the estimated likelihoodthat building collapse will occur if the building issubjected to the maximum considered earthquakeground motions for the region. The BasicStructural Hazard Scores are based on the damageand loss estimation functions provided in theFEMA-funded HAZUS damage and lossestimation methodology (NIBS, 1999). For moreinformation about the development of the BasicStructural Hazard Scores, see the companionFEMA 155 report (ATC, 2002).The Basic Structural Scores are provided oneach Data Collection Form in the first row of the24 3: Completing the Data Collection Form FEMA 154

the fifteen model building types, along with aphotograph of a sample exterior view, and theBasic Structural Scores for regions of low (L),moderate (M), and high (H) seismicity areprovided in Table 3-1.Additional background information on thephysical characteristics and earthquakeperformance of these building types, not essentialto the RVS procedure, is provided in Appendix E.Figure 3-7.Portion of Data CollectionForm containing BasicStructural Hazard Scores.structural scoring matrix in the lower portion ofthe Data Collection Form (see Figure 3-7). In highand moderate seismicity regions, these scoresapply to buildings built after the initial adoptionand enforcement of seismic codes, but before therelatively recent significant improvement of codes(that is, before the applicable benchmark year, asdefined in Table 2-2). In low seismicity regions,they apply to all buildings except those designedand constructed after the applicable benchmarkyear, as defined in Table 2-2.A key issue to be addressed in the planningstage (as recommended in Section 2.4.2) is theidentification of those years in which seismiccodes were initially adopted and later significantlyimproved. If the RVS authority in high andmoderate seismicity regions is unsure of theyear(s) in which codes were initially adopted, thedefault year for all but PC1 (tiltup) buildings is1941, (the default year specified in the HAZUScriteria, NIBS, 1999). For PC1 (tiltup) buildings,the initial year in which effective seismic codeswere specified is 1973 (ICBO, 1973). Asdescribed in Sections 3.8.5 and 3.8.6, the DataCollection Form includes Score Modifiers thatprovide a means for modifying the BasicStructural Hazard Score as a function of designand construction date.Brief summaries of the physical characteristicsand expected earthquake performance of each of3.7.2 Identifying the Lateral-Force-Resisting SystemAt the heart of the RVS procedure is the task ofidentifying the lateral-force-resisting system fromthe street. Once the lateral-force-resisting systemis identified, the screener finds the appropriatealpha-numeric code on the Data Collection Formand circles the Basic Structural Hazard Scoreimmediately beneath it (see Figure 3-7).Ideally, the lateral-force-resisting system foreach building to be screened would be identifiedprior to field work through the review andinterpretation of construction documents for eachbuilding (i.e., during the planning stage, asdiscussed in Section 2.7).If prior determination of the lateral-forceresistingsystem is not possible through the reviewof building plans, which is the most likelyscenario, this determination must be made in thefield. In this case, the screener reviews spacingand size of windows, and the apparentconstruction materials to determine the lateralforceresisting system. If the screener cannotidentify with complete assuredness the lateralforce-resistingsystem from the street, the screenershould enter the building interior to verify thebuilding type selected (see Section 3.7.3 foradditional information on this issue.)If the screener cannot determine the lateralforce-resistingsystem, and access to the interior isnot possible, the screener should eliminate thoselateral-force-resisting systems that are not possibleand assume that any of the others are possible. Inthis case the Basic Structural Hazard Scores for allpossible lateral-force-resisting systems would becircled on the Data Collection Form. Moreguidance and options pertaining to this issue areprovided in Section 3.9.FEMA 154 3: Completing the Data Collection Form 25

Table 3-1Build Type Descriptions, Basic Structural Hazard Scores, and Performance in Past EarthquakesBuildingIdentifierPhotographBasic StructuralHazard ScoreCharacteristics and PerformanceW1Light woodframe residentialandcommercialbuildingsequal to orsmaller than5,000 squarefeetH = 2.8M = 5.2L = 7.4●●●Wood stud walls are typicallyconstructed of 2-inch by 4-inch vertical wood membersset about 16 inches apart (2-inch by 6-inch for multiplestories).Most common exterior finishmaterials are wood siding,metal siding, or stucco.Buildings of this type performedvery well in past earthquakesdue to inherentqualities of the structural systemand because they arelightweight and low rise.●Earthquake-induced cracks inthe plaster and stucco (if any)may appear, but are classifiedas non-structural damage.●The most common type ofstructural damage in olderbuildings results from a lack ofconnection between thesuperstructure and the foundation,and inadequate chimneysupport.W2Light woodframe buildingsgreaterthan 5,000square feetH = 3.8M =4.8L = 6.0●These are large apartmentbuildings, commercial buildingsor industrial structuresusually of one to three stories,and, rarely, as tall as six stories.26 3: Completing the Data Collection Form FEMA 154

Table 3-1BuildingIdentifierS1SteelmomentresistingframeS2Braced steelframeBuild Type Descriptions, Basic Structural Hazard Scores, and Performance in Past Earthquakes(Continued)PhotographBasic StructuralHazard ScoreH = 2.8M = 3.6L = 4.6H = 3.0M = 3.6L = 4.8Characteristics and PerformanceTypical steel moment-resistingframe structures usuallyhave similar bay widths inboth the transverse and longitudinaldirections, around20-30 ft.The floor diaphragms are usuallyconcrete, sometimes oversteel decking. This structuraltype is used for commercial,institutional and public buildings.The 1994 Northridge and1995 Kobe earthquakesshowed that the welds in steelmoment- frame buildingswere vulnerable to severedamage. The damage took theform of broken connectionsbetween the beams and columns.These buildings are bracedwith diagonal members,which usually cannot bedetected from the buildingexterior.Braced frames are sometimesused for long and narrowbuildings because of their stiffness.From the building exterior, it isdifficult to tell the differencebetween steel momentframes, steel braced frames,and steel frames with interiorconcrete shear walls.In recent earthquakes, bracedframes were found to havedamage to brace connections,especially at the lowerlevels.●●●●●●●Zoom-in of upper photoFEMA 154 3: Completing the Data Collection Form 27

Table 3-1BuildingIdentifierS3Light metalbuildingBuild Type Descriptions, Basic Structural Hazard Scores, and Performance in Past Earthquakes(Continued)PhotographBasic StructuralHazard ScoreH = 3.2M = 3.8L = 4.6Characteristics and PerformanceThe structural system usuallyconsists of moment frames inthe transverse direction andbraced frames in the longitudinaldirection, with corrugatedsheet-metal siding. Insome regions, light metalbuildings may have partialheightmasonry walls.The interiors of most of thesebuildings do not have interiorfinishes and their structuralskeleton can be seeneasily.Insufficient capacity of tensionbraces can lead to their elongationand consequent buildingdamage duringearthquakes.Inadequate connection to aslab foundation can allow thebuilding columns to slide onthe slab.Loss of the cladding canoccur.●●●●●S4Steel frameswith cast-inplaceconcreteshearwallsH = 2.8M = 3.6L = 4.8●●●Lateral loads are resisted byshear walls, which usually surroundelevator cores and stairwells,and are covered byfinish materials.An interior investigation willpermit a wall thickness check.More than six inches in thicknessusually indicates a concretewall.Shear cracking and distresscan occur around openings inconcrete shear walls duringearthquakes.●Wall construction joints canbe weak planes, resulting inwall shear failure belowexpected capacity.28 3: Completing the Data Collection Form FEMA 154

Table 3-1BuildingIdentifierS5Steel frameswith unreinforcedmasonry infillwallsBuild Type Descriptions, Basic Structural Hazard Scores, and Performance in Past Earthquakes(Continued)PhotographBasic StructuralHazard ScoreH = 2.0M = 3.6L = 5.0Characteristics and PerformanceSteel columns are relativelythin and may be hidden inwalls.Usually masonry is exposedon exterior with narrow piers(less than 4 ft wide) betweenwindows.Portions of solid walls willalign vertically.Infill walls are usually two tothree wythes thick.Veneer masonry around columnsor beams is usuallypoorly anchored and detacheseasily.●●●●●●All exposed concrete framesare reinforced concrete (notsteel frames encased in concrete).C1ConcretemomentresistingframesH = 2.5M = 3.0L = 4.4●●A fundamental factor governingthe performance of concretemoment-resisting framesis the level of ductile detailing.Large spacing of ties in columnscan lead to a lack ofconcrete confinement andshear failure.●Lack of continuous beam reinforcementcan result in hingeformation during load reversal.●The relatively low stiffness ofthe frame can lead to substantialnonstructural damage.●Column damage due topounding with adjacent buildingscan occur.FEMA 154 3: Completing the Data Collection Form 29

Table 3-1BuildingIdentifierC2Concreteshear wallbuildingsBuild Type Descriptions, Basic Structural Hazard Scores, and Performance in Past Earthquakes(Continued)PhotographBasic StructuralHazard ScoreH = 2.8M = 3.6L = 4.8Characteristics and PerformanceConcrete shear-wall buildingsare usually cast in place, andshow typical signs of cast-inplaceconcrete.Shear-wall thickness rangesfrom 6 to 10 inches.These buildings generally performbetter than concreteframe buildings.They are heavier than steelframebuildings but more rigiddue to the shear walls.Damage commonly observedin taller buildings is caused byvertical discontinuities,pounding, and irregular configuration.●●●●●C3Concreteframes withunreinforcedmasonry infillwallsH =1.6M = 3.2L = 4.4●●●●Concrete columns and beamsmay be full wall thickness andmay be exposed for viewingon the sides and rear of thebuilding.Usually masonry is exposedon the exterior with narrowpiers (less than 4 ft wide)between windows.Portions of solid walls willalign vertically.This type of construction wasgenerally built before 1940 inhigh-seismicity regions butcontinues to be built in otherregions.●Infill walls tend to buckle andfall out-of-plane when subjectedto strong lateral out-ofplaneforces.●Veneer masonry around columnsor beams is usuallypoorly anchored and detacheseasily.30 3: Completing the Data Collection Form FEMA 154

Table 3-1BuildingIdentifierPC1Tilt-up buildingsBuild Type Descriptions, Basic Structural Hazard Scores, and Performance in Past Earthquakes(Continued)PhotographBasic StructuralHazard ScoreH = 2.6M = 3.2L = 4.4Characteristics and PerformanceTilt-ups are typically one ortwo stories high and are basicallyrectangular in plan.Exterior walls were traditionallyformed and cast on theground adjacent to their finalposition, and then “tilted-up”and attached to the floor slab.The roof can be a plywooddiaphragm carried on woodpurlins and glulam beams or alight steel deck and joist system,supported in the interiorof the building on steel pipecolumns.Weak diaphragm-to-wallanchorage results in the wallpanels falling and the collapseof the supported diaphragm(or roof).●●●●Partial roof collapse due to failed diaphragm-to-wallconnectionFEMA 154 3: Completing the Data Collection Form 31

Table 3-1BuildingIdentifierPC2Precast concreteframebuildingsBuild Type Descriptions, Basic Structural Hazard Scores, and Performance in Past Earthquakes(Continued)PhotographBuilding under constructionBasic StructuralHazard ScoreH = 2.4M = 3.2L = 4.6●●●●●●●Characteristics and PerformancePrecast concrete frames are,in essence, post and beamconstruction in concrete.Structures often employ concreteor reinforced masonry(brick or block) shear walls.The performance varieswidely and is sometimes poor.They experience the sametypes of damage as shear wallbuildings (C2).Poorly designed connectionsbetween prefabricated elementscan fail.Loss of vertical support canoccur due to inadequate bearingarea and insufficient connectionbetween floorelements and columns.Corrosion of metal connectorsbetween prefabricated elementscan occur.Detail of the precast componentsBuilding nearing completion32 3: Completing the Data Collection Form FEMA 154

Table 3-1BuildingIdentifierRM1Reinforcedmasonrybuildings withflexible diaphragmsBuild Type Descriptions, Basic Structural Hazard Scores, and Performance in Past Earthquakes(Continued)PhotographBasic StructuralHazard ScoreH = 2.8M = 3.6L = 4.8Characteristics and Performance● Walls are either brick or concreteblock.● Wall thickness is usually 8inches to 12 inches.● Interior inspection is requiredto determine if diaphragmsare flexible or rigid.● The most common floor androof systems are wood, lightsteel, or precast concrete.● These buildings can performwell in moderate earthquakesif they are adequately reinforcedand grouted, with sufficientdiaphragm anchorage.● Poor construction practice canresult in ungrouted and unreinforcedwalls, which will faileasily.Truss-joists support plywood and lightweightconcrete slabDetail showing reinforced masonryFEMA 154 3: Completing the Data Collection Form 33

Table 3-1BuildingIdentifierRM2Reinforcedmasonrybuildings withrigid diaphramsBuild Type Descriptions, Basic Structural Hazard Scores, and Performance in Past Earthquakes(Continued)PhotographBasic StructuralHazard ScoreH = 2.8M = 3.4L = 4.6Characteristics and Performance● Walls are either brick or concreteblock.● Wall thickness is usually 8inches to 12 inches.● Interior inspection is requiredto determine if diaphragmsare flexible or rigid.● The most common floor androof systems are wood, lightsteel, or precast concrete.● These buildings can performwell in moderate earthquakesif they are adequately reinforcedand grouted, with sufficientdiaphragm anchorage.● Poor construction practice canresult in ungrouted and unreinforcedwalls, which will faileasily.●These buildings often usedweak lime mortar to bond themasonry units together.URMUnreinforcedmasonrybuildingsH = 1.8M = 3.4L = 4.6●●Arches are often an architecturalcharacteristic of olderbrick bearing wall buildings.Other methods of spanningare also used, including steeland stone lintels.●Unreinforced masonry usuallyshows header bricks in thewall surface.●The performance of this typeof construction is poor due tolack of anchorage of walls tofloors and roof, soft mortar,and narrow piers betweenwindow openings.34 3: Completing the Data Collection Form FEMA 154

Determining the lateral-force-resistingsystem in the field is often difficult. A usefulfirst step is to determine if the building structureis a frame or a bearing wall. Examples of framestructures and bearing wall structures are shownin Figure 3-8, 3-9, and 3-10.Information to assist the screener indistinguishing if the building is a bearing wallor frame structure is provided in the side bar.Once this determination has been made and theFigure 3-8Figure 3-9Typical frame structure. Featuresinclude: large window spans,window openings on manysides, and clearly visible columnbeamgrid pattern.Typical bearing wall structure.Features include small windowspan, at least two mostly solid walls,and thick load-bearing walls.Distinguishing Between Frame and Bearing Wall BuildingSystems.A frame structure (for example, S1, S2, S3, S4, C1, PC2) is madeup of beams and columns throughout the entire structure, resistingboth vertical and lateral loads. A bearing wall structure (forexample, PC1 and URM) uses vertical-load-bearing walls, whichare more or less solid, to resist the vertical and lateral loads.When a building has large openings on all sides, it isprobably a frame structure as opposed to a bearing wall structure.A common characteristic of a frame structure is the rectangulargrid patterns of the facade, indicating the location of the columnsand girders behind the finish material. This is particularlyrevealing when windows occupy the entire opening in the frame,and no infill wall is used. A newer multistory commercialbuilding should be assumed to be a frame structure, even thoughthere may exist interior shear walls carrying the lateral loads (thiswould be a frame structure with shear walls).Bearing wall systems carry vertical and lateral loads withwalls rather than solely with columns. Structural floor memberssuch as slabs, joists, and beams, are supported by load-bearingwalls. A bearing wall system is thus characterized by more or lesssolid walls and, as a rule of thumb, a load-bearing wall will havemore solid areas than openings. It also will have no wideopenings, unless a structural lintel is used.Some bearing-wall structures incorporate structural columns,or are partly frame structures. This is especially popular inmultistory commercial buildings in urban lots where girders andcolumns are used in the ground floor of a bearing wall structure toprovide larger openings for retail spaces. Another example iswhere the loads are carried by both interior columns and aperimeter wall. Both of these examples should be considered asbearing wall structures, because lateral loads are resisted by thebearing walls. Bearing wall structures sometimes utilize only twowalls for load bearing. The other walls are non-load-bearing andthus may have large openings. Therefore, the openness of thefront elevation should not be used to determine the structure type.The screener should also look at the side and rear facades. If atleast two of the four exterior walls appear to be solid then it islikely that it is a bearing wall structure.Window openings in older frame structures can sometimes bemisleading. Since wide windows were excessively costly andfragile until relatively recently, several narrow windows separatedby thin mullions are often seen in older buildings. These thinmullions are usually not load bearing. When the narrow windowsare close together, they constitute a large opening typical of aframe structure, or a window in a bearing wall structure with steellintels.Whereas open facades on all sides clearly indicate a framestructure, solid walls may be indicative of a bearing wall structureor a frame structure with solid infill walls. Bearing walls areusually much thicker than infill walls, and increase in thickness inthe lower stories of multi-story buildings. This increase in wallthickness can be detected by comparing the wall thickness atwindows on different floors. Thus, solid walls can be identifiedas bearing or non-bearing walls according to their thickness, if thestructural material is known.A bearing wall system is sometimes called a box system.FEMA 154 3: Completing the Data Collection Form 35

lateral-force-resisting systems that are not possibleand assume that any of the others are possible.Example of a Frame BuildingExample of a Bearing Wall StructureFigure 3-10 Frame and bearing wall structuresprincipal structural material is identified, theessential information for determining the lateralforce-resistingsystem has been established. It isthen useful to know that:• unreinforced masonry and tilt-up buildings areusually bearing-wall type,• steel buildings and pre-cast concrete buildingsare usually frame type, and• concrete and reinforced masonry buildingsmay be either type.A careful review of Table 3-1 and theinformation provided in Appendices D and E,along with training by knowledgeable buildingdesign professionals, should assist the screener inthe determination of lateral-force-resistingsystems. There will be some buildings for whichthe lateral-force-resisting system cannot beidentified because of their facade treatment. Inthis case, the screener should eliminate those3.7.3 Interior InspectionsIdeally, whenever possible, the screener shouldseek access to the interior of the building toidentify, or verify, the lateral-force-resistingsystem for the building. In the case of reinforcedmasonry buildings, entry is particularly importantso that the screener can distinguish between RM1buildings, which have flexible floor and roofdiaphragms, and RM2 buildings, which have rigidfloor and roof diaphragms.As with the exterior inspection, the interiorprocess should be performed in a logical manner,either from the basement to the roof, or roof tobasement. The screener should look at each floorthoroughly.The RVS procedure does not require theremoval of finish materials that are otherwisepermanently affixed to the structure. There are anumber of places within a building where it ispossible to see the exposed structure. Thefollowing are some ways to determine thestructure type.1. If the building has a basement that is notoccupied, the first-floor framing may beexposed. The framing will usually berepresentative of the floor framing throughoutthe building.2. If the structural system is a steel or concreteframe, the columns and beams will often beexposed in the basement. The basement wallswill likely be concrete, but this does not meanthat they are concrete all the way to the roof.3. High and mid-rise structures usually have oneor more levels of parking below the building.When fireproofed steel columns and girdersare seen, the screener can be fairly certain thatthe structure is a steel building (S1, S2, or S4see Figure 3-11).4. If the columns and beams are constructed ofconcrete, the structure type is most likely aconcrete moment-frame building (C1, seeFigure 3-12). However, this is not guaranteedas some buildings will use steel framing abovethe ground floor. To ascertain the buildingtype, the screener will need to look at thecolumns above the first floor.5. If there is no basement, the mechanicalequipment rooms may show what the framingis for the floor above.36 3: Completing the Data Collection Form FEMA 154

Figure 3-11 Interior view showing fireproofedcolumns and beams,which indicate a steelbuilding (S1, S2, or S4).6. If suspended ceilings are used, one of theceiling tiles can be lifted and simply pushedback. In many cases, the floor framing willthen be exposed. Caution should be used inidentifying the framing materials, becauseprior to about 1960, steel beams were encasedin concrete to provide fireproofing. If steelframing is seen with what appears to beconcrete beams, most likely these are steelbeams encased in concrete.7. If plastered ceilings are observed abovesuspended ceilings, the screener will not beable to identify the framing materials;however, post-1960 buildings can beeliminated as a possibility because thesebuildings do not use plaster for ceilings.8. At the exterior walls, if the structural system isa frame system, there will be regularly spacedfurred out places. These are the buildingcolumns. If the exterior walls between thecolumns are constructed of brick masonry andthe thickness of the wall is 9 inches or more,the structure type is either steel frame withunreinforced masonry infill (S5) or concreteframe with unreinforced masonry infill (C3).9. Pre-1930 brick masonry buildings that are sixstories or less in height and that have woodfloorframing supported on masonry ledges inpockets formed in the wall are unreinforcedmasonry bearing-wall buildings (URM).3.7.4 Screening Buildings with More ThanOne Lateral-Force-Resisting SystemIn some cases, the screener may observe buildingshaving more than one lateral-force-resistingsystem. Examples might include a wood-framebuilding atop a precast concrete parking garage, ora building with reinforced concrete shear walls inone direction and a reinforced moment-resistingframe in the other.Buildings that incorporate more than onelateral-force-resisting system should be evaluatedfor all observed types of structural systems, andthe lowest Final Structural Score, S, shouldgovern.Figure 3-12 Interior view showing concrete columns and girders, which indicate a concrete moment frame (C1).FEMA 154 3: Completing the Data Collection Form 37

Score Modifiercircled in the appropriate column (i.e., under thereference code for the identified lateral-forceresistingsystem for that building).Following are descriptions of eachperformance attribute, along with guidance onhow to recognize each from the street. If aperformance attribute does not apply to a givenbuilding type, the Score Modifier is indicated with“N/A”, which indicates “not applicable.”3.8.1 Mid-Rise BuildingsIf the building has 4 to 7 stories, it is considered amid-rise building, and the score modifierassociated with this attribute should be circled.Figure 3-13.Portion of Data Collection Formcontaining attributes that modifyperformance and associated scoremodifiers.3.8 Identifying Seismic PerformanceAttributes and Recording ScoreModifiersThis section discusses major factors thatsignificantly impact structural performance duringearthquakes, and the assignment of ScoreModifiers related to each of these factors(attributes). The severity of the impact onstructural performance varies with the type oflateral-force-resisting system; thus the assignedScore Modifiers depend on building type. ScoreModifiers associated with each performanceattribute are indicated in the scoring matrix on theData Collection Form (see Figure 3-13). ScoreModifiers for the building being screened are3.8.2 High-Rise BuildingsIf the building has 8 or more stories, it isconsidered a high-rise building, and the scoremodifier associated with this attribute should becircled.3.8.3 Vertical IrregularityThis performance attribute applies to all buildingtypes. Examples of vertical irregularity includebuildings with setbacks, hillside buildings, andbuildings with soft stories (see illustrations ofexample vertical irregularities in Figure 3-14).If the building is irregularly shaped inelevation, or if some walls are not vertical, thenapply the modifier (see example in Figure 3-15).If the building is on a steep hill so that overthe up-slope dimension of the building the hillrises at least one story height, a problem may existbecause the horizontal stiffness along the lowerside may be different from the uphill side. Inaddition, in the up-slope direction, the stiff shortcolumns attract the seismic shear forces and mayfail. In this case the performance modifier isapplicable. See Figure 3-14 for an example.38 3: Completing the Data Collection Form FEMA 154

Figure 3-14SetbacksHillsideSoft StoryElevation views showing vertical irregularities, with arrows indicating locations of particular concern.A soft story exists if the stiffness of one storyis dramatically less than that of most of the others(see Figure 3-15). Examples are shear walls orinfill walls not continuous to the foundation. Softstories are difficult to verify without knowledge ofhow the building was designed and how the lateralforces are to be transferred from story to story. Inother words, there may be shear walls in thebuilding that are not visible from the street.However, if there is doubt, it is best to beconservative and indicate the existence of a softstory by circling the vertical irregularity ScoreModifier. Use an asterisk and the commentsection to explain the source of uncertainty. Inmany commercial buildings, the first story is softdue to large window openings for displaypurposes. If one story is particularly tall or haswindows on all sides, and if the stories above havefewer windows, then it is probably a soft story.A building may be adequate in one directionbut be “soft” in the perpendicular direction. Forexample, the front and back walls may be open butthe side walls may be solid. Another commonexample of soft story is “tuck under” parkingcommonly found in apartment buildings (seeFigure 3-16). Several past earthquakes inCalifornia have shown the vulnerability of thistype of construction.Vertical irregularity is a difficult characteristicto define, and considerable judgment andexperience are required for identification purposes.SetbackSoft StoryFigure 3-15Example of setbacks (see Figure 3-14) and a soft first story.FEMA 154 3: Completing the Data Collection Form 39

Figure 3-163.8.4 Plan IrregularityExample of soft story conditions,where parking requirements resultin large weak openings.If a building has a vertical or plan irregularity, asdescribed below, this modifier applies. Planirregularity can affect all building types.Examples of plan irregularity include buildingswith re-entrant corners, where damage is likely tooccur; buildings with good lateral-load resistancein one direction but not in the other; and buildingswith major stiffness eccentricities in the lateralforce-resistingsystem, which may cause twisting(torsion) around a vertical axis.Buildings with re-entrant corners include thosewith long wings that are E, L, T, U, or + shaped(see Figures 3-17 and 3-18). See SEAOC (1996)for further discussion of this issue.)Plan irregularities causing torsion areespecially prevalent among corner buildings, inwhich the two adjacent street sides of the buildingare largely windowed and open, whereas the othertwo sides are generally solid. Wedge-shapedbuildings, triangular in plan, on corners of streetsnot meeting at 90°, are similarly susceptible (seeFigure 3-19).Although plan irregularity can occur in allbuilding types, primary concern lies with wood,tilt-up, pre-cast frame, reinforced masonry andunreinforced masonry construction. Damage atconnections may significantly reduce the capacityof a vertical-load-carrying element, leading topartial or total collapse.3.8.5 Pre-CodeThis Score Modifier applies for buildings in highand moderate seismicity regions and is applicableif the building being screened was designed andconstructed prior to the initial adoption andenforcement of seismic codes applicable for thatbuilding type (e.g., steel moment frame, S1). Theyear(s) in which seismic codes were initiallyadopted and enforced for the various modelbuilding types should have been identified as partL-Shaped T-Shaped U-ShapedWeak Link Between LargerLarge OpeningBuilding Plan AreasFigure 3-17 Plan views of various building configurations showing plan irregularities; arrows indicate possibleareas of damage.40 3: Completing the Data Collection Form FEMA 154

Figure 3-18 Example of a building, with a planirregularity, with two wings meeting atright angles.of the Data Collection Form review process duringthe pre-planning stage (as recommended inSection 2.4.2). If this determination was not madeduring the planning stage, the default year is 1941,for all building types except PC1, in which case itis 1973. Because of the method used to calculatethe Basic Structural Hazard Scores, this modifierdoes not apply to buildings in the low seismicityregion.3.8.6 Post-BenchmarkThis Score Modifier is applicable if the buildingbeing screened was designed and constructed aftersignificantly improved seismic codes applicablefor that building type (e.g., concrete momentframe, C1) were adopted and enforced by the localjurisdiction. The year in which suchimprovements were adopted is termed the“benchmark” year. Benchmark year(s) for thevarious model building types should have beenidentified as part of the Data Collection Formreview process during the pre-planning stage (asrecommended in Section 2.4.2). Benchmark yearsfor the various building types (designed inaccordance with various model codes) areprovided in Table 2-2.3.8.7 Soil Type C, D, or EScore Modifiers are provided for Soil Type C,Type D, and Type E. The appropriate modifiershould be circled if one of these soil types exists atthe site (see Section 3.4 for additional discussionregarding the determination of soil type). Ifsufficient guidance or data are not available duringthe planning stage to classify the soil type as AFigure 3-19 Example of a building, triangular inplan, subject to torsion.through E, a soil type E should be assumed.However, for one- or two-story buildings with aroof height equal to or less than 25 feet, a class Dsoil type may be assumed if the actual siteconditions are not known.There is no Score Modifier for Type F soilbecause buildings on soil type F cannot bescreened effectively by the RVS procedure. Ageotechnical engineer is required to confirm thesoil type F and an experienced professionalengineer is required for building evaluation.3.9 Determining the Final ScoreThe Final Structural Score, S, is determined for agiven building by adding (or subtracting) theScore Modifiers for that building to the BasicStructural Hazard Score for the building. Theresult is documented in the section of the formentitled Final Score (see Figure 3-20). Based onthis information, and the “cut-off” score selectedduring the pre-planning process (see Section2.4.3), the screener then decides if a detailedevaluation is required for the building and circles“YES” or “NO” in the lower right-hand box (seeFigure 3-20). Additional guidance on this issue isprovided in Sections 4.1, and 4.2.When the screener is uncertain of the buildingtype, an attempt should be made to eliminate allunlikely building types. If the screener is still leftwith several choices, computation of the FinalStructural Score S may be treated several ways:1. The screener may calculate S for all theremaining options and choose the lowestFEMA 154 3: Completing the Data Collection Form 41

detailed field inspection would includeentering the building, and examining thebasement, roof, and all structural elements.Which of these two options the RVS authoritywishes to adopt should be decided in the RVSplanning phase (see Section 2.3).Figure 3-20 Location on Data Collection Formwhere the final score, comments, andan indication if the building needsdetailed evaluation are documented.score. This is a conservative approach, andhas the disadvantage that it may be tooconservative and the assigned score mayindicate that the building presents a greaterrisk than it actually does. This conservativeapproach will not pose problems in caseswhere all the possible remaining buildingtypes result in scores below the cut-off value.In all these cases the building hascharacteristics that justify further reviewanyway by a design professional experiencedin seismic design.2. If the screener has little or no confidenceabout any choice for the structural system, thescreener should write DNK below the word“Building Type” (see Figure 3-7), whichindicates the screener does not know. In thiscase there should be an automatic default tothe need for a detailed review of the buildingby an experienced design professional. A more3.10 Photographing the BuildingAt least one photograph of the building should betaken for identification purposes. The screener isnot limited to one photograph. A photographcontains much more information, although perhapsless emphasized, than the elevation sketch. Largebuildings are difficult to photograph from thestreet and the camera lens introduces distortion forhigh-rise buildings. If possible, the photographshould be taken from a sufficient distance toinclude the whole building, and such that adjacentfaces are included. A wide angle or a zoom lensmay be helpful. Strong sunlit facades should beavoided, as harsh contrasts between shadows andsunlit portions of the facade will be introduced.Lastly, if possible, the front of the building shouldnot be obscured by trees, vehicles or other objects,as they obscure the lower (and often the mostimportant) stories.3.11 Comments SectionThis last section of the form (see Figure 3-20) isfor recording any comments the screener maywish to make regarding the building, occupancy,condition, quality of the data or unusualcircumstances of any type. For example, if not allsignificant details can be effectively photographedor drawn, the screener could describe additionalimportant information in the comments area.Comments may be made on the strength of mortarused in a masonry wall, or building features thatcan be seen at or through window openings. Otherexamples where comments are helpful aredescribed throughout Chapter 3.42 3: Completing the Data Collection Form FEMA 154

Chapter 4Using the RVS Procedure ResultsThe rapid visual screening procedure presented inthis Handbook is meant to be the preliminaryscreening phase of a multi-phase procedure foridentifying earthquake-hazardous buildings.Buildings identified by this procedure aspotentially hazardous must be analyzed in moredetail by an experienced seismic designprofessional. Because rapid visual screening isdesigned to be performed from the street, withinterior inspection not always possible, hazardousdetails will not always be visible, and seismicallyhazardous buildings may not be identified as such.Conversely, buildings identified as potentiallyhazardous may prove to be adequate.Since the original publication of FEMA 154 in1988, the RVS procedure has been widely used bylocal communities and government agencies. Acritical issue in the implementation of FEMA 154has been the interpretation of the Final StructuralScore, S, and the selection of a “cut-off” score,below which a detailed seismic evaluation of thebuilding by a design professional in seismic designis required.Following are discussions on: (1) interpretationand selection of the “cut-off” score; (2) prioruses of the FEMA 154 RVS procedure, includingdecisions regarding the “cut-off” score; and (3)other possible uses of the FEMA 154 RVSprocedure, including resources needed for thevarious possible uses. These discussions areintended to illuminate both the limitations andpotential applications of the RVS procedure.4.1 Interpretation of RVS ScoreHaving employed the RVS procedure anddetermined the building’s Final Structural Score,S, which is based on the Basic Structural HazardScore and Score Modifiers associated with thevarious performance attributes, the RVS authorityis naturally faced with the question of what these Sscores mean. Fundamentally, the final S score isan estimate of the probability (or chance) that thebuilding will collapse if ground motions occur thatequal or exceed the maximum consideredearthquake (MCE) ground motions (the currentFEMA 310 ground motion specification fordetailed seismic evaluation of buildings). Theseestimates of the score are based on limitedobserved and analytical data, and the probabilityof collapse is therefore approximate. For example,a final score of S = 3 implies there is a chance of 1in 10 3 , or 1 in 1000, that the building will collapseif such ground motions occur. A final score of S =2 implies there is a chance of 1 in 10 2 , or 1 in 100,that the building will collapse if such groundmotions occur. (Additional information about thebasis for the RVS scoring system is provided inthe second edition of the companion FEMA 155Report, Rapid Visual Screening of Buildings forPotential Seismic Hazards: SupportingDocumentation.) An understanding andappreciation of the physical essence of the scoringsystem, as described above, will facilitate theinterpretation of results from implementation ofthe RVS procedure.4.2 Selection of RVS “Cut-Off” ScoreOne of the most difficult issues pertaining to rapidvisual screening is answering the question, “Whatis an acceptable S?” This is a question for thecommunity that involves the costs of safety versusthe benefits. The costs of safety include:• the costs of reviewing and investigating indetail hundreds or thousands of buildings inorder to identify some fraction of those thatwould actually sustain major damage in anearthquake; and• the costs associated with rehabilitating thosebuildings finally determined to beunacceptably weak.The most compelling benefit is the saving of livesand prevention of injuries due to reduced damagein those buildings that are rehabilitated. Thisreduced damage includes not only less materialdamage, but fewer major disruptions to daily livesand businesses. The identification of hazardousbuildings and the mitigation of their hazards arecritical because there are thousands of existingbuildings in all parts of the United States that maysuffer severe damage or possible collapse in theevent of strong ground shaking. Such damage orFEMA-154 4: Using the RVS Procedure Results 43

collapse can be accompanied by loss of life andserious injury. In a great earthquake deaths couldnumber in the thousands.Each community needs to engage in someconsideration of these costs and benefits ofseismic safety, and decide what value of S is anappropriate “cut-off’ for their situation. The finaldecision involves many non-technical factors, andis not straightforward. Perhaps the bestquantification of the risk inherent in modernbuilding codes was a study regarding designpractice by the National Bureau of Standards(NBS, 1980), which observed:In selecting the target reliability it wasdecided, after carefully examining theresulting reliability indices for the manydesign situations, that a β 0 =3 is arepresentative average value for manyfrequently used structural elements when theyare subjected to gravity loading, while β 0=2.5 and β 0 = 1.75 are representative valuesfor loads that include wind and earthquake,respectively 3 .In other words, present design practice is suchthat a value of S of about 3 is appropriate for dayto-dayloadings, and a value of about 2, orsomewhat less, is appropriate for infrequent, butpossible, earthquake loadings.More recently, recommendations for seismicdesign criteria for new steel moment-framebuildings (SAC, 2000) concluded that:…it is believed that…structures designed inaccordance with [these recommendations]provide in excess of 90% confidence of beingable to withstand [shaking that has a 2%probability of exceedance in 50 years] withoutglobal collapse….This statement can be shown to be equivalent tothe findings in the NBS (1980) study.Unless a community itself considers the costand benefit aspects of seismic safety, an S value ofabout 2.0 is a reasonable preliminary value to usewithin the context of RVS to differentiateadequate buildings from those potentiallyinadequate and thus requiring detailed review. Useof a higher cut-off S value implies greater desiredsafety but increased community-wide costs forevaluations and rehabilitation; use of a lower valueof S equates to increased seismic risk and lower3 β 0 as used in the National Bureau of Standards studyis approximately equivalent to S as used herein.short-term community-wide costs for evaluationsand rehabilitation (prior to an earthquake).Further guidance on cost and other societalimplications of seismic rehabilitation of hazardousbuildings is available in other publications of theFEMA report series on existing buildings (seeFEMA-156 and FEMA-157, Typical Costs forSeismic Rehabilitation of Buildings, 2 nd Edition,Volumes 1 and 2, and FEMA-255 and FEMA-256,Seismic Rehabilitation of Federal Buildings – ABenefit/Cost Model, Volumes 1 and 2 (VSP,1994).4.3 Prior Uses of the RVS ProcedureDuring the decade following publication of thefirst edition of the FEMA 154 Handbook, the rapidvisual screening procedure was used by privatesectororganizations and government agencies toevaluate more than 70,000 buildings nationwide(ATC, 2002). As reported at the FEMA 154 UsersWorkshop in San Francisco in September 2000(see second edition of FEMA 155 report foradditional information), these applicationsincluded surveys of (1) commercial buildings inBeverly Hills, California, (2) National ParkService facilities, (3) pubic buildings anddesignated shelters in southern Illinois; (4) U. S.Army facilities, (5) facilities of the U. S.Department of the Interior and (6) buildings inother local communities and for other governmentagencies. The results from some of these effortsare described below.In its screening of 11,500 buildings using theFEMA 154 RVS procedure, the U. S. Army Corpsof Engineers Civil Engineering ResearchLaboratory (CERL) used a cut-off score of 2.5,rather than 2.0 (S. Sweeney, oral communication,September 2000), with the specific intent of usinga more conservative approach. As a result of theFEMA 154 screening, approximately 5,000buildings had final S scores less than 2.5. Thesebuildings, along with a subset of buildings that hadFEMA 154 scores higher than 2.5, but were ofconcern for other reasons, were further evaluatedin detail using the FEMA 178 NEHRP Handbookfor the Seismic Evaluation of Existing Buildings[BSSC, 1992]). Results from the subsequentFEMA 178 evaluations indicated that somebuildings that failed the FEMA 154 RVSprocedure (that is, had scores less than 2.5) did notfail the FEMA 178 evaluations and that some thatpassed the FEMA 154 RVS procedure (withscores higher than 2.5) did not pass the FEMA 178evaluation (that is, were found to have inadequateseismic resistance). This finding emphasizes the44 4: Using the RVS Procedure Results FEMA-154

concern identified at the beginning of this chapterthat the use of FEMA 154 may not identifypotentially earthquake hazardous buildings assuch, and that buildings identified as potentiallyhazardous may prove to be adequate.Other conclusions and recommendationspertaining to the use of the FEMA 154 RVSprocedure that emanated from these applicationsincluded the following:• Involve design professionals in RVSimplementation whenever possible to ensurethat the lateral-force-resisting structuralsystems are correctly identified (suchidentification is particularly difficult inbuildings that have been remodeled and addedto over the years);• Conduct intensive training for screeners sothat they fully understand how to implementthe methodology, in all of its aspects;• Inspect both the exterior and, if at all possible,the interior of the building;• Review construction drawings as part of thescreening process;• Review soils information prior toimplementation of the methodology in thefield; and• Interpret the results from FEMA 154screenings in a manner consistent with thelevel of resources available for the screening(for example, cut-off scores may be dictatedby budget constraints).Most of these recommendations were incorporatedin the updated RVS procedure described in thisHandbook.4.4 Other Possible Uses of the RVSProcedureIn addition to identifying potentiallyseismically hazardous buildings needing furtherevaluation, results from RVS surveys can also beused for other purposes, including: (1) designingseismic hazard mitigation programs for acommunity (or agency); (2) ranking acommunity’s (or agency’s) seismic rehabilitationneeds; (3) developing inventories of buildings foruse in regional earthquake damage and loss impactassessments; (4) developing inventories ofbuildings for use in planning postearthquakebuilding safety evaluation efforts; and (5)developing building-specific seismic vulnerabilityinformation for purposes such as insurance rating,decision making during building ownershiptransfers, and possible triggering of remodelingrequirements during the permitting process.Following are descriptions of how RVS resultscould be used for several of these purposes.4.4.1 Using RVS Scores as a Basis forHazardous Building MitigationProgramsCommunities need to develop hazard mitigationplans to establish a solid foundation for thedetailed seismic evaluation and rehabilitation ofbuildings. In developing any hazardous buildingsmitigation program, the cost effectiveness of theseismic evaluation and rehabilitation work must bedetermined. The costs should be evaluated againstthe direct benefits of the seismic rehabilitationprogram (that is, reduced physical damage,reduced injuries and loss of life). Additionally,secondary benefits to the community should beconsidered with the direct benefits. Thesesecondary benefits are difficult to quantify indollars, but must be considered. Secondarybenefits are those that apply to the community as awhole. Examples include:• reduced interruption to business;• reduced potential for secondary damage (forexample, fires) that could impact otherwiseundamaged structures;• reduced potential for traffic flow problemsaround areas of significant damage; and• other reduced economic impacts.The process of selecting buildings to berehabilitated begins with the determination of thecut-off Structural Score, S, below which detailedbuilding seismic evaluation is required (e.g., byuse of the FEMA 310 procedures). Such adetermination allows estimates to be made on thecosts of additional seismic evaluation andrehabilitation work. From this the benefits aredetermined. The most cost-effective solution willbe the one where the least amount is spent in directcosts to gain the greatest direct and secondarybenefits.After the RVS authority establishes theappropriate cut-off score and completes thescreening process, it needs to determine the bestway to notify building owners of the need formore review of buildings that score less than thecut-off (if the authority is not the owner of thebuildings being screened). At the same time thecommunity needs to develop the appropriatestandards (for example, adoption of FEMA 356,FEMA 154 4: Using the RVS Procedure Results 45

Prestandard and Commentary on the SeismicRehabilitation of Buildings [ASCE, 2000]) toaccomplish the goal of the mitigation program.Ultimately, the mitigation program needs toaddress those buildings that represent the largestpotential threat to life safety and the community.Timelines for compliance with the new standardsand the mitigation program should be developedon a priority basis, such that the first priorityactions relate to those buildings posing the mostsignificant risk, after which those posing a lesserrisk are addressed.4.4.2 Using RVS Data in CommunityBuilding Inventory DevelopmentRVS data can be used to establish buildinginventories that characterize a community’sseismic risk. For example, RVS data could beused to improve the HAZUS (NIBS, 1999)characterization of the local inventory, which has adefault level based on population, economicfactors, and regional trends. Similarly, RVS couldbe incorporated directly into a community’sGeographic Information System (GIS), allowingthe community to generate electronic and papermaps that reflect the building stock of thecommunity. Electronic color coding of the varioustypes of buildings under the RVS authority, basedon their ultimate vulnerability, allows thecommunity to see at a glance where the vulnerableareas of the community are found.4.4.3 Using RVS Data to Plan PostearthquakeBuilding-Safety-Evaluation EffortsIn a postearthquake environment one of the initialresponse priorities is to determine rapidly thesafety of buildings for continued occupancy. Theprocedure most often used is that represented inthe ATC-20 Report, Procedures forPostearthquake Safety Evaluation of Buildings(ATC, 1989, 1995). This procedure is similar innature to that of the RVS procedure in that initialrapid evaluations are performed to find thosebuildings that are obviously unsafe (Red placard)and those that have no damage or damage thatdoes not pose a threat to continued occupancy(Green placard). All other buildings fall into acondition where occupancy will need to berestricted in some form (Yellow placard).The database developed following thecompletion of the RVS process in a givencommunity will be valuable in setting thepriorities of where safety evaluation will beperformed first, after a damaging earthquake. Forexample, a community could use HAZUSsoftware, in combination with RVS-basedinventory information, to determine areas wheresignificant damage may exist for variousearthquake scenarios. Similarly, a communitycould use an existing GIS containing RVSinventory data and computer-generated maps ofstrong ground shaking, such as the ShakeMapsdeveloped by the USGS (ATC, in progress), toestimate the location and distribution of damagedbuildings. With such information, communityofficials would be able to determine those areaswhere building safety evaluations should beconducted.Later, the data collected during thepostearthquake building safety evaluations couldbe added to the RVS authority’s RVS-basedbuilding inventory database. Using GIS, maps canthen be prepared showing the damage distributionwithin the community based on actual buildingdamage. Building locations could beelectronically color-coded in accordance with thecolor of the safety-evaluation placard that isplaced on the building: Green, Yellow, or Red.4.4.4 Resources Needed for the VariousUses of the RVS ProcedureFor most applications of the RVS procedure,the resources needed to implement the process aresimilar, consisting principally of an RVS manager(the RVS authority), technical specialists to trainscreeners, a team of screeners, materials to betaken into the field (e.g., the Handbook and otheritems listed in Section 2.8), and buildingconstruction drawings. Most applications areassisted by the development and maintenance of acomputerized database for recordkeeping and theuse of geographic information systems (GIS). Amatrix showing recommended resources forvarious FEMA 154 RVS applications is providedin Table 4-1.46 4: Using the RVS Procedure Results FEMA-154

Table 4-1Application1. Rankingseismicrehabilitationneeds2. Designingseismic hazardmitigationprograms3. Developinginventories forregionalearthquakedamage andloss studies4. Planningpostearthquakebuilding safetyevaluationeffortsMatrix of Recommended Personnel and Material Resources for Various FEMA 154 RVSApplications*RVSManagerRVSTrainerScreenersResourcesScreeningEquipmentandSuppliesBuildingDrawingsComputerizedRecordKeepingSystemX X X X X X XX X X X X X XX X X X X X XX X X X X X X5. DevelopingbuildingspecificX X X X Xvulnerabilityinformation*It is recommended that rapid visual screening projects be carried out under the oversight of a design professionalwith significant experience in seismic design.GISFEMA 154 4: Using the RVS Procedure Results 47

Chapter 5Example Applicationof Rapid Visual ScreeningPresented in this chapter is an illustrativeapplication of the rapid visual screening procedurein the hypothetical community of Anyplace USA.The RVS implementation process (as depicted inFigure 2-1) is described, from budget developmentto selection of the appropriate Data CollectionForm, to the screening of individual buildings inthe field. Prior to implementation of the RVSprocedure, the RVS authority (the Building andPlanning Department of Anyplace) has reviewedthe Handbook and established the purpose for theRVS.5.1 Step 1: Budget and CostEstimationThe RVS authority has been instructed by the citycouncil to conduct the RVS process to identify allbuildings in the city, excluding detached singlefamilyand two-family dwellings, that arepotentially earthquake hazardous and that shouldbe further evaluated by a design professionalexperienced in seismic design (the principalpurpose of the RVS procedure). It is understoodthat, depending on the results of the RVS, the citycouncil may adopt future ordinances that establishpolicy on when, how and by whom low-scoringbuildings should be evaluated and on futureseismic rehabilitation requirements. It is alsodesired that the results from the RVS beincorporated in the geographic information systemthat the city recently installed to map and describefacilities throughout the city, including allbuildings and utility systems within the city limits.The RVS authority has determined there areapproximately 1,000 buildings in the city that arenot detached single-family or two-familydwellings and that some of the buildings are atleast 100 years old. The RVS authority plans(1) to conduct a pre-field data collection andevaluation process to examine and assessinformation in its existing files and to documentbuilding location, size, use, and other informationon the Data Collection Forms prior to fieldscreening; (2) to review available building plansprior to field screening; (3) to inspect the interiorsof buildings whenever possible; (4) to establish anelectronic RVS record-keeping system that iscompatible with its GIS; and (5) to train screenersprior to sending them into the field.Costs to conduct these activities have beenestimated, assuming an average of $40 per hour(salary plus benefits) for personnel who performdata evaluation, screening, and recordmanagement. Costs are in 2001 dollars. It isassumed that three persons will carry out the prefielddata collection and evaluation process, thatfour two-person teams of design professionals willconduct the review of building plans and the fieldscreening, that two persons will file all screeningdata, and that the entire RVS process will takeapproximately six months. Based on these ratesand assumed times to conduct the variousactivities, the following RVS budget has beenestablished:1. Pre-field data collection, evaluation,and processing (1,000 buildings ×0.4 hr/building × $40/hr) $16,0002. Training, including trainer time(24 hours), screener time (8 hoursper screener), and materials 4,0003. Review of available building plans(500 plan sets × 0.75 hr/plan set× $40/hr) 15,0004. Field screening (1,000 buildings× 0.75 hr/building × $40/hr) 30,0005. Record-keeping systemdevelopment 5,0006. Electronic filing of Data CollectionForms, including verification ofdata input (1,000 forms ×0.75 hour/form × $40/hour) 30,0007. Subtotal $100,0008. Management (10% of item 7) 10,0009. Total $110,000FEMA 154 5: Example Application of Rapid Visual Screening 49

5.2 Step 2: Pre-Field PlanningDuring the pre-field planning process the RVSauthority confirmed that the existing geographicinformation system was capable of beingexpanded to include RVS-related information andresults. In addition, the RVS authority decidedthat sufficient soil information was available fromthe State Geologist to develop an overlay for theirGIS containing soils information for the entirecity. While not required as part of the RVSprocess, it was also determined that the cityincluded an area that had isolated pockets of lowliquefaction potential, and that there was no areawith landslide potential. Consequently the RVSauthority concluded that GIS overlays for liquefactionand landslide potential were not warranted.The RVS authority also verified that theexisting GIS had reference tables containingaddress information for most of the properties inthe city (developed earlier from the tax assessor’sfiles) and that these tables could be extracted andincluded in a new GIS-compatible electronicrelational database containing the RVS results. Itwas also determined that other building andplanning department’s files contained reliableinformation on building name, use, size (heightand area), structural system, and age for buildingsbuilt or remodeled within the last 30 years, andthat Sanborn maps, which contain size, age, andother building attribute information (see Section2.6.3) were available (at the local library) for mostof the downtown sector.Based on this information, the RVS authorityconfirmed its prior preliminary decision underStep 1 to develop an electronic RVS recordkeeping system (relational database) that could beimported into the existing GIS. The RVSauthority also decided to focus on the downtownsector of Anyplace during the initial phase of theRVS field work, and to expand to the outlyingareas later.5.3 Step 3: Selection and Review ofthe Data Collection FormTo choose the correct Data Collection Form, theRVS authority elected to establish the seismicityfor Anyplace USA by using Method 2 (see Section2.4.1), rather than by selecting the seismicityregion from the maps in Appendix A. Method 2,using the zip-code option, provides more precisionthan the Appendix A maps which use countyboundaries. Method 2 was executed by accessingthe USGS seismic hazard web site(http://geohazards.cr.usgs.gov/eq/), selectingHazard by Zip Code, entering the zip code, 91234,and obtaining spectral acceleration (SA) values for0.2 second and 1.0 second for ground motionshaving a 2% probability of being exceeded in 50years (see Figure 5-1). The values of 2.10 g and0.88 g for 0.2 second and 1.0 second, respectively,were multiplied by 2/3 to obtain the reducedvalues of 1.40 g and 0.59 g, respectively, for 0.2The input zip-code is 91234.ZIP CODE 91234LOCATION33.7754 Lat. -118.1860 Long.DISTANCE TO NEAREST GRID POINT 3.0229 kmsNEAREST GRID POINT33.8 Lat. -118.2 Long.Probabilistic ground motion values, in %g, at the Nearest Gridpoint are:10%PE in 50 yr 5%PE in 50 yr 2%PE in 50 yrPGA 51.809940 70.680931 96.4769590.2 sec SA 118.997299 157.833496 210.0034030.3 sec SA 114.200897 148.213104 194.6349951.0 sec SA 42.566330 60.786320 88.084427Figure 5-1 Screen capture of USGS web page showing SA values for 0.2 sec and 1.0 sec for groundmotions having 2% probability of being exceeded in 50 years (values shown in boxes).50 5: Example Application of Rapid Visual Screening FEMA 154

second and 1.0 second. These reduced values werecompared to the criteria in Table 2-1 to determinethat the reduced (using the 2/3 factor) USGSassigned motions met the “high seismicity” criteriafor both short-period and long-period motions(that is, 1.40 g is greater than 0.5 g for the 0.2second [short-period] motions, and 0.59 g isgreater than 0.2 g for the 1.0 second [long-period]motions). All other zip codes in Anyplace weresimilarly input to the USGS web site, and theresults indicated high seismicity in all cases. Onthis basis the RVS authority selected the DataCollection Form for high seismicity (Figure 5-2).Using the checklist of Table 2-3, the RVSauthority reviewed the Data Collection Form todetermine if the occupancy categories andoccupancy loads were useful for their purposesand evaluated other parameters on the form,deciding that no changes were needed. The RVSauthority also conferred with the chief buildingofficial, the department’s plan checkers, and localdesign professionals to establish key seismic codeadoption dates for the various building lateralload-resistingsystems considered by the RVS andfor anchorage of heavy cladding. It wasdetermined that Anyplace adopted seismic codesfor W1, W2, S1, S5, C1, C3, RM1, and RM2building types in 1933, and that seismic codeswere never adopted for URM buildings (after 1933they were no longer permitted to be built). For S2,S3, S4 and PC2 buildings, it was assumed forpurposes of the RVS procedure that seismic codeswere adopted in 1941, using the default yearrecommended in Section 2.4.2. For PC1buildings, it was assumed that seismic codes werefirst adopted in 1973 (per the guidance provided inSection 2.4.2). It was also determined thatseismically rehabilitated URM buildings should betreated as buildings designed in accordance with aseismic code (that is, treated as if they weredesigned in 1933 or thereafter). Because Anyplacehas been consistently adopting the UniformBuilding Code since the early 1960s, benchmarkyears for all building types, except URM, weretaken from the “UBC” column in Table 2-2. Theyear in which seismic anchorage requirements forheavy cladding was determined to be 1967. Thesefindings were indicated on the Quick ReferenceGuide (See Figure 5-3).5.4 Step 4: Qualifications andTraining for ScreenersAnyplace USA selected RVS screeners from twosources: the staff of the Department of Buildingand Planning, and junior-level engineers fromlocal engineering offices, who were hired on atemporary consulting basis. Training was carriedout by one of the department’s most experiencedplan checkers, who spent approximately 24 hoursreading the FEMA 154 Handbook and preparingtraining materials.As recommended in this Handbook, thetraining was conducted in a classroom setting andconsisted of: (1) discussions of lateral-forceresistingsystems and how they behave whensubjected to seismic loads; (2) how to use the DataCollection Form and the Quick Reference Guide;(3) a review of the Basic Structural Hazard Scoresand Score Modifiers; (4) what to look for in thefield; (5) how to account for uncertainty; and (6)an exercise in which screeners were shown interiorand exterior photographs of buildings and asked toidentify the lateral-load-resisting system andvertical and plan irregularities. The training classalso included focused group interaction sessions,principally in relation to the identification ofstructural systems and irregularities using exteriorand interior photographs. Screeners were alsoinstructed on items to take into the field.5.5 Step 5: Acquisition and Reviewof Pre-Field DataAs described in the Pre-Field Planning process(Step 2 above), the RVS authority of AnyplaceUSA already had electronic GIS reference tablescontaining street addresses and parcel numbers formost of the buildings in the city. These data(addresses and parcel numbers) were extractedfrom the electronic GIS system (see screen captureof GIS display showing parcel number and otheravailable information for an example site, Figure5-4) and imported into a standard off-the-shelfelectronic database as a table. To facilitate laterFEMA 154 5: Example Application of Rapid Visual Screening 51

Figure 5-2High seismicity Data Collection Form selected for Anyplace, USA.52 5: Example Application of Rapid Visual Screening FEMA 154

Figure 5-3Quick Reference Guide for Anyplace USA showing entries for years in which seismic codes were firstadopted and enforced and benchmark years.FEMA 154 5: Example Application of Rapid Visual Screening 53

Figure 5-4Property information at example site in city’s geographic information system.use in the GIS, the street addresses weresubdivided into the following fields: the numericpart of the address; the street prefix (for example,“North”); the street name; and the street suffix (forexample, “Drive”). A zip code field was added,zip codes for each street address were obtainedusing zip code lists available from the US PostalService, and these data were also added to thedatabase. This process yielded 950 streetaddresses, with parcel number and zip code,andestablished the initial information inAnyplace’s electronic “Building RVS Database”.Permitting files, which contained data onbuildings constructed or remodeled within the last30 years (including parcel number), were thenreviewed to obtain information on building name(if available), use, building height (height in feetand number of stories), total floor area, age (yearbuilt), and structural system. This process yieldedinformation (from paper file folders) onapproximately 500 buildings. Fields were addedto the Building RVS Database for each of theseattributes and data were added to the appropriaterecords (searching on parcel number) in thedatabase; in the case of structure type, the entryincluded an asterisk to denote uncertainty. If anaddress was missing in the database, a new recordcontaining that address and related data wasadded. On average, 30 minutes per building wererequired to extract the correct information fromthe permitting files and insert it into the electronicdatabase.The city’s librarian provided copies ofavailable Sanborn maps, which were reviewed toidentify information on number of stories, yearbuilt, building size (square footage), building use,and limited information on structural type forapproximately 200 buildings built prior to 1960.These data were added to the appropriate record(searching on address) in the Building RVSDatabase; in the case of structure type, the entryincluded an asterisk to denote uncertainty. If anaddress was missing in the database, a new recordcontaining that address and related data wasadded. For this effort, 45 minutes per building, onaverage, were required to extract the correctinformation from the Sanborn maps and insert itinto the electronic database.During the pre-fielddata collection and review process the RVSauthority also obtained an electronic file of soilsdata (characterized in terms of the soil typesdescribed in Section 2.6.6) from the StateGeologist and created an overlay of thisinformation in the city’s GIS system. Pointsdefined by the addresses in the GIS referencetables (including newly identified addresses addedto the references tables as a result of the abovecitedefforts) were combined with the soils typeoverlay, and soil type was then assigned to eachpoint (address) by a standard GIS operating54 5: Example Application of Rapid Visual Screening FEMA 154

procedure. The soils type information for eachaddress was then transferred back to the BuildingRVS Database table into a new field for eachbuilding’s soil type.Based on the above efforts, Anyplace’sBuilding RVS Database was expanded to includeapproximately 1,000 records with address, parcelnumber, zip code, and soils information, andapproximately 700 of these records also containedinformation on building name (if any), use,number of stories, total floor area, year built, andstructure type.5.6 Step 6: Review of ConstructionDocumentsFortuitously, the city had retained microfilmcopies of building construction documentssubmitted with each permit filing during the last30 years, and copies of these documents wereavailable for 500 buildings (the same subsetdescribed in Step 5 above). Teams consisting ofone building department staff member and oneconsulting engineer reviewed these documents toverify, or identify, the lateral-force-resistingsystem for each building. Any new or revisedinformation on structure type derived as part ofthis process was then inserted in the Building RVSDatabase, in which case, previously existinginformation in this field, along with the associatedasterisk denoting uncertainty, was removed. Onaverage, this effort required approximately 30minutes per plan set, including databasecorrections.5.7 Step 7: Field Screening ofBuildingsImmediately prior to field screening (that is, at theconclusion of Step 6 above), the RVS authorityacquired an electronic template of the DataCollection Form from the web site of the AppliedTechnology Council (www.atcouncil.org) andused this template to create individual DataCollection Forms for each record in the BuildingRVS Database. Each form contained uniqueinformation in the building identification portionof the form, with “Parcel Number” shown as“Other Identifiers” information (see Figure 5-2).In those instances where structure typeinformation was included in the database, thisinformation was also added as “Other Identifiers”information, with an asterisk if still uncertain. Soiltype information was indicated on each form bycircling the appropriate letter (and briefdescription) in the “Soil Type” section of the form(see Figure 5-2).The Data Collection Forms, including blankforms for use with buildings not yet in theBuilding RVS Database, were distributed to theRVS screeners along with their RVS assignments(on a block-by-block basis). Screeners wereadvised that some of the database informationprinted on the form (e.g., number of stories,structure type denoted with an *) would need to beverified in the field, that approximately 700 of the1,000 Data Collection Forms had substantiallycomplete, but not necessarily verified, informationin the location portion of the form, and that all1,000 forms had street, address, parcel number, zipcode, and soil type information.Prior to field work, each screener wasreminded to complete the Data Collection Form ateach site before moving on to the next site,including adding his or her name as the screenerand the screening date (in the buildingidentification section of the form).Following are several examples illustratingrapid visual screening in the field and completionof the Data Collection Form. Some examples useforms containing relatively complete buildingidentification information, including structuretype, obtained during the pre-field data acquisitionand review process (Step 5); others use formscontaining less complete building identificationinformation; and still others use blank formscompletely filled in at the site.Example 1: 3703 Roxbury StreetUpon arriving at the site the screenersobserved the building as a whole (Figure 5-5) andbegan the process of verifying the information inthe building identification portion of the form(upper right corner), starting with the streetaddress. The building’s lateral-force-resistingsystem (S2, steel braced frame) was verified bylooking at the building with binoculars (see Figure5-6). The number of stories (10), use (office), andyear built (1986) were also confirmed byinspection. The base dimensions of the buildingwere estimated by pacing off the distance alongeach face, assuming 3 feet per stride, resulting inthe determination that it was 75 ft x 100 ft in plan.FEMA 154 5: Example Application of Rapid Visual Screening 55

Figure 5-6Close-up view of 3703 Roxbury Streetexterior showing perimeter braced steelframing.Figure 5-5Exterior view of 3703 Roxbury Street.On this basis, the listed square footage of 76,000square feet was verified as correct (see Figure5-7). The screeners also added their names andthe date of the field screening to the buildingidentification portion of the form.A sketch of the plan and elevation views of thebuilding were drawn in the “Sketch” portion of theform.The building use was circled in the“Occupancy” portion, and from Section 3 of theQuick Reference Guide, the occupancy load wasestimated at 75,000/150 = 500. Hence, theoccupancy range of 101-1000 was circled.No falling hazards were observed, as glasscladding is not considered as heavy cladding.The next step in the process was to circle theappropriate Basic Structural Hazard Score and theappropriate Score Modifiers. Having verified thelateral-force-resisting system as S2, this code wascircled along with the Basic Structural Scorebeneath it (see Figure 5-8). Because the buildingis high rise (8 stories or more) this modifier wascircled. Noting that the soil is type D, as alreadydetermined during the pre-field data acquisitionphase and indicated in the Soil Type portion of theform, the modifier for Soil Type D was circled.By adding the column of circled numbers, a FinalScore of 3.2 was determined. Because this scorewas greater than the cut-off score of 2.0, thebuilding did not require a detailed evaluation by anexperienced seismic design professional. Lastly,an instant camera photo of the building wasattached to the form.Figure 5-7Building identification portion of Data Collection Form for Example 1, 3703 Roxbury Street.56 5: Example Application of Rapid Visual Screening FEMA 154

Figure 5-8Completed Data Collection Form for Example 1, 3703 Roxbury Street.FEMA 154 5: Example Application of Rapid Visual Screening 57

Example 2: 3711 Roxbury StreetUpon arrival at the site, the screeners observed thebuilding as a whole (Figure 5-9). Unlike Example1, there was little information in the buildingidentification portion of the form (only streetaddress, zip code, and parcel number wereprovided). The screeners determined the numberof stories to be 12 and the building use to becommercial and office. They paced off thebuilding plan dimensions to estimate the plan sizeto be 58 feet x 50 feet. Based on this information,the total square footage was estimated to be34,800 square feet (12 x 50 x 58), and the numberof stories, use, and square footage were written onthe form. Based on a review of information inAppendix D of this Handbook, the year ofconstruction was estimated to be 1944 and thisdate was written on the form.A sketch of the plan and elevation views of thebuilding were drawn in the “Sketch” portion of theform.The building use was circled in the“Occupancy” portion, and from Section 3 of theQuick Reference Guide, the occupancy load wasestimated at 34,800/135 ♦ = 258. Hence, theoccupancy range of 101-1000 was circled.The cornices at roof level were observed, andentered on the form.Noting that the estimated construction datewas 1944 and that it was a 12-story building , areview of the material in Table D-6 (Appendix D),indicated that the likely options for building typewere S1, S2, S5, C1, C2, or C3. On more carefulexamination of the building exterior with the useof binoculars (see Figure 5-10), it was determinedthe building was type C3, and this alpha-numericcode, and accompanying Basic Structural Score,were circled on the Data Collection Form.Because the building was high-rise (more than7 stories), this modifier was circled, and becausethe four individual towers extending above thebase represented a vertical irregularity, thismodifier was circled. Noting that the soil is typeD, as already determined during the pre-field dataacquisition phase and indicated in the Soil Typeportion of the form, the modifier for Soil Type Dwas circled.By adding the column of circled numbers, aFinal Score of 0.5 was determined. Because thisscore was less than the cut-off score of 2.0, thebuilding required a detailed evaluation by anexperienced seismic design professional. Lastly,♦ The “135” value is the approximate average of themid-range occupancy load for commercial buildings(125 sq. ft. per person) and the mid-range occupancyload for office buildings (150 sq. ft. per person).an instant camera photo of the building wasattached to the Data Collection Form (a completedversion of the form is provided in Figure 5-11).Figure 5-9Exterior view of 3711 Roxbury.Figure 5-10 Close-up view of 3711 RoxburyStreet building exterior showinginfill frame construction.58 5: Example Application of Rapid Visual Screening FEMA 154

Figure 5-11Completed Data Collection Form for Example 2, 3711 Roxbury Street.FEMA 154 5: Example Application of Rapid Visual Screening 59

Example 3: 5020 Ebony DriveExample 3 was a high-rise residential building(Figure 5-12) in a new part of the city in whichnew development had begun within the last fewyears. The building was not included in theelectronic Building RVS Database, andconsequently there was not a partially preparedData Collection Form for this building. Based onvisual inspection, the screeners determined that thebuilding had 22 stories, including a tall-storypenthouse, estimated that it was designed in 1996,and concluded that its use was both commercial(in the first story) and residential in the upperstories. The screeners paced off the building plandimensions to estimate the plan size to beapproximately 270 feet x 180 feet. Based on thisinformation and considering the symmetric butnon-rectangular floor plan, the total square footagewas estimated to be 712,800 square feet. Thesedata were written on the form, along with thenames of the screeners and the date of thescreening. The screeners also drew a sketch of aportion of the plan view of the building in thespace on the form allocated for a “Sketch”.The building use (commercial and residential)was circled in the “Occupancy” portion, and fromSection 3 of the Quick Reference Guide, theoccupancy load was estimated at 712,800/200 =3,564. Based on this information, the occupancyrange of 1000+ was circled.While the screeners reasonably could haveassumed a type D soil, which was the condition atthe adjacent site approximately ½ mile away, theyconcluded they had no basis for assigning a soiltype. Hence they followed the instructions in theHandbook (Section 3.4), which specifies that ifthere is no basis for assigning a soil type, soil typeE should be assumed. Accordingly, this soil typewas circled on the form.Given the design date of 1996, the anchoragefor the heavy cladding on the exterior of thebuilding was assumed to have been designed tomeet the anchorage requirements initially adoptedin 1967 (per the information on the QuickReference Guide). No other falling hazards wereobserved.The window spacing in the upper stories andthe column spacing at the first floor level indicatedthe building was either a steel moment-framebuilding, or a concrete moment-frame building.The screeners attempted to view the interior butwere not provided with permission to do so. Theyelected to indicate that the building was either anS1 or C1 type on the Data Collection Form andFigure 5-12Exterior view of 5020 Ebony Drive.circled both types, along with their BasicStructural Scores. In addition, the screenerscircled the modifiers for high rise (8 stories ormore) and post-benchmark year, given that theestimated design date (1996) occurred after thebenchmark years for both S1 and C1 buildingtypes (per the information on the Quick ReferenceGuide). They also circled the modifier for soiltype E (in both the S1 and C1 columns).By adding the circled numbers in both the S1and C1 columns, Final Scores of 3.6 and 3.3respectively were determined for the two buildingtypes. Because both scores were greater than thecut-off score of 2.0, a detailed evaluation of thebuilding by an experienced seismic designprofessional was not required. Before leaving thesite, the screeners photographed the building andattached the photo to the Data Collection Form. Acompleted version of the Data Collection Form isprovided in Figure 5-13.60 5: Example Application of Rapid Visual Screening FEMA 154

Figure 5-13Completed Data Collection Form for Example 3, 5020 Ebony Drive.FEMA 154 5: Example Application of Rapid Visual Screening 61

Figure 5-14Example 4: 1450 Addison AvenueExterior view of 1450 Addison Avenue.The building at 1450 Addison Avenue (see Figure5-14) was a 1-story commercial building designedin 1990, per the information provided in thebuilding identification portion of the DataCollection Form. By inspection the screenersconfirmed the address, number of stories, use(commercial), and year built (Figure 5-15). Thescreeners paced off the building plan dimensionsto estimate the plan size (estimated to be 10,125square feet), confirming the square footage shownon the identification portion of the form. The L-shaped building was drawn on the form, alongwith the dimensions of the various legs.The building’s commercial use was circled inthe “Occupancy” portion, and from Section 3 ofthe Quick Reference Guide, the occupancy loadwas estimated at 10,200/125 = 80. Hence, theoccupancy range of 11-100 was circled. No fallinghazards were observed.The building type (W2) was circled on theform along with its Basic Structural Score.Because the building was L-shaped in plan themodifier for plan irregularity was circled. Becausesoil type C had been circled in the Soil Type box(based on the information in the Building RVSDatabase) the modifier for soil type C was circled.By adding the column of circled numbers, aFinal Score of 5.3 was determined. Because thisscore was greater than the cut-off score of 2.0, thebuilding did not require a detailed evaluation by anexperienced seismic design professional. Lastly,an instant camera photo of the building wasattached to the Data Collection Form. Acompleted version of the form is provided inFigure 5-16.Figure 5-15Building identification portion of Data Collection Form for Example 4, 1450 Addison Avenue.62 5: Example Application of Rapid Visual Screening FEMA 154

Figure 5-16Completed Data Collection Form for Example 4, 1450 Addison Avenue.FEMA 154 5: Example Application of Rapid Visual Screening 63

5.8 Step 8: Transferring the RVSField Data to the ElectronicBuilding RVS DatabaseThe last step in the implementation of rapid visualscreening for Anyplace USA was transferring theinformation on the RVS Data Collection Formsinto the relational electronic Building RVSDatabase. This required that all photos andsketches on the forms be scanned and numbered(for reference purposes), and that additional fields(and tables) be added to the database for thoseattributes not originally included in the database.For quality control purposes, data wereentered separately into two different versions ofthe electronic database, except photographs andsketches, which were scanned only once. Adouble-entry data verification process was thenused, whereby the data from one database werecompared to the same entries in the seconddatabase to identify those entries that were notexactly the same. Non-identical entries wereexamined and corrected as necessary. The entireprocess, including scanning of sketches andphotographs, required approximately 45 minutesper Data Collection Form.After the electronic Building RVS Databasewas verified, it was imported into the city’s GIS,thereby providing Anyplace with a state-of-the-artcapability to identify and plot building groupsbased on any set of criteria desired by the city’spolicy makers. Photographs and sketches ofindividual buildings could also be shown in theGIS simply by clicking on the dot or symbol usedto represent each building and selecting thedesired image.64 5: Example Application of Rapid Visual Screening FEMA 154

Appendix AMaps ShowingSeismicity RegionsFEMA 154 A: Maps Showing Seismicity Regions 65

Figure A-1 Seismicity Regions of the Conterminous United States.66 A: Maps Showing Seismicity Regions FEMA 154

Figure A-2Seismicity Regions in California, Idaho, Nevada, Oregon, and Washington.FEMA 154 A: Maps Showing Seismicity Regions 67

Figure A-3Seismicity Regions in Arizona, Montana, Utah, and Wyoming.68 A: Maps Showing Seismicity Regions FEMA 154

Figure A-4Seismicity Regions in Colorado, Kansas, New Mexico, Oklahoma,and Texas.FEMA 154 A: Maps Showing Seismicity Regions 69

Figure A-5Seismicity Regions in Iowa, Michigan, Minnesota, Nebraska, North Dakota, South Dakota,and Wisconsin.70 A: Maps Showing Seismicity Regions FEMA 154

Figure A-6Seismicity Regions in Illinois, Indiana, Kentucky, Missouri, and Ohio.FEMA 154 A: Maps Showing Seismicity Regions 71

Figure A-7Seismicity Regions in Alabama, Arkansas, Louisiana, Mississippi,and Tennessee.72 A: Maps Showing Seismicity Regions FEMA 154

Figure A-8Seismicity Regions in Connecticut, Maine, Massachusetts,New Hampshire, New York, Rhode Island, and Vermont.FEMA 154 A: Maps Showing Seismicity Regions 73

Figure A-9Seismicity Regions in Delaware, Maryland, New Jersey,Pennsylvania, Virginia, and West Virginia.74 A: Maps Showing Seismicity Regions FEMA 154

Figure A-10Seismicity Regions in Florida, Georgia, North Carolina, andSouth Carolina.FEMA 154 A: Maps Showing Seismicity Regions 75

Figure A-11Seismicity Regions in Alaska and Hawaii.76 A: Maps Showing Seismicity Regions FEMA 154

Appendix BData Collection Forms andQuick Reference GuideFEMA 154 B: Data Collection Forms and Quick Reference Guide 77

Appendix CReview of Design andConstruction DrawingsDrawing styles vary among engineering offices, butthe conventions used are very consistent. The followingare some of the common designations:1. Around the perimeter of the building, the exteriorwalls will be shown as a double line, if the spacebetween the lines is empty, this will usually be awood stud wall.2. Concrete walls will be shaded.3. Masonry walls will be cross hatched.4. Horizontal beams and girders will be shown witha solid line for steel and wood, and a double solidor dotted line for concrete.● Steel framing will have a notation of shape,depth, and weight of the member. The designationswill include W, S, I, B and severalothers followed by the depth in inches, an“x,” and the weight in pounds per lineal foot.An example would be W8x10 (wide flangeshape, 8” deep, 10 lbs/ft).● Wood framing will have the width and depthof the member. An example would be 4x10(4” wide and 10” deep). Floor joists and roofrafters will be shown with the same call-outexcept not all members will be shown. Afew at each end of the area being framed willshow and there will be an arrow showing theextent and the call-out of the size members.● Concrete framing will have the width anddepth. Where steel and wood are shown assingle line, concrete will be shown as a doubleline. An example of the call out wouldbe 12x24 (12” wide and 24” deep). Additionally,or in lieu of the number call-out, themember might be given a letter and number(B-1 or G-1) with a reference to a schedulefor the size and reinforcing. “B” stands forbeam and “G” stands for girder. Usually,beams are smaller than girders and spanbetween girders while girders will be largerand frame between columns.5. Columns will show on the floor plans as theirshape with a shading designation where appropriate:● Steel column will be shown as an “H”rotated to the correct orientation for the locationon the plan.● Wood column will be an open square.● Concrete column will be either a square or acircle depending on the column configuration.The square or circle will beshaded.6. Steel moment frames will show the columns witha heavy line between the columns representingthe beam or girder. At each end of the beam orgirder at the column will be a small triangleshaded. This indicates that the connectionbetween the beam or girder and the column isfully restrained.FEMA 154 C: Review of Design and Construction Drawings 83

Appendix DExterior Screening for SeismicSystem and AgeD.1 IntroductionA successful evaluation of a building is dependent onthe screener’s ability to identify accurately the constructionmaterials, lateral-force-resisting system,age, and other attributes that would modify its earthquakeperformance (e.g., vertical or plan irregularities).This appendix includes discussions ofinspection techniques that can be used while viewingfrom the street.D.2 What to Look for and How to Find ItIt may be difficult to identify positively the structuraltype from the street as building veneers often maskthe structural skeleton. For example, a steel frameand a concrete frame may look similar from the outside.Features typical of a specific type of structuremay give clues for successful identification. In somecases there may be more than one type of framepresent in the structure. Should this be the case, thepredominant frame type should be indicated on theform.Following are attributes that should be consideredwhen trying to determine a building lateralforce-resistingsystem from the street:1. Age: The approximate age of a building can indicatethe possible structure type, as well as indicatingthe seismic design code used during thebuilding design process. Age is difficult to determinevisually, but an approximation, accuratewithin perhaps a decade, can be estimated bylooking at the architectural style and detail treatmentof the building exterior, if the facade hasnot been renovated. If a building has been renovated,the apparent age is misleading. See SectionD.3 for additional guidance.2. Facade Pattern: The type of structure can sometimesbe deduced by the openness of the facade,or the size and pattern of window openings. Thefacade material often can give hints to the structurebeneath. Newer facade materials likely indicatethat modern construction types were used inthe design and may indicate that certain buildingtypes can be eliminated.3. Height: The number of stories will indicate thepossible type of construction. This is particularlyuseful for taller buildings, when combined withknowledge of local building practice. See SectionD.4 for additional guidance.4. Original Use: The original use can, at times, givehints as to the structural type. The original usecan be inferred from the building character, if thebuilding has not been renovated. The present usemay be different from the original use. This isespecially true in neighborhoods that havechanged in character. A typical example of this iswhere a city’s central business district has grownrapidly, and engulfed what were once industrialdistricts. The buildings’ use has changed andthey are now either mixed office, commercial orresidential (for office workers).D.3 Identification of Building AgeThe ability to identify the age of a building by consideringits architectural style and construction materialsrequires an extensive knowledge of architecturalhistory and past construction practice. It is beyondthe scope of this Handbook to discuss the variousstyles and construction practices. Persons involved inor interested in buildings often have a general knowledgeof architectural history relevant to their region.Interested readers should refer to in-depth texts formore specific information.Photographs, architectural character, and age of(1) residential, (2) commercial, and (3) mixed useand miscellaneous buildings, are illustrated inTables D-1 through D-3, respectively. Photographsof several example steel frame and concrete framebuildings under construction are provided inFigure D-1. The screener should study these photographsand characteristics closely to assist in differentiatingarchitectural styles and facade treatment ofvarious periods. Facade renovation (see photos b andc in Figure D-1) can clearly alter the original appearance.When estimating building age, the screenershould look at the building from all sides as facaderenovation often occurs only at the building front. Anew building will seldom look like an old one. ThatFEMA 154 D: Exterior Screening for Seismic System and Age 85

Table D-1Photographs, Architectural Characteristics, and Age of Residential Buildingsa. 1965-1980Examplesb. 1965-1980CharacteristicsLow-Rise Buildings(1-3 stories):●Typically wood ormasonry● May have groundfloor or basementparking, a soft story● Older buildings typicallyhave morearchitectural detail,ornamentation● 1950s and later aremore ‘modern’ −lacking ornamentation,typically withmore horizontallinesCommon structuraltypes: W2, RM1, RM2,URMc. 1965-1980d. 1960-1975 reinforced concreteshear wallMid-Rise (4-7 stories)and High-RiseBuildings (8 storiesand higher):● Typically, reinforcedconcrete(older, URM)● May have commercialground floor, asoft story● Older buildings typicallyhave morecornices, architecturaldetail, ornamentation● 1950s and later arelacking ornamentation,typically withstronger vertical orhorizontal linesCommon structuraltypes: W2, RM1, RM2,URMe. Pre-1933 URM (rehabilitated)86 D: Exterior Screening for Seismic System and Age FEMA 154

Table D-2Illustrations, Architectural Characteristics, and Age of Commercial Structuresa. Pre-1930ExamplesPre-1950Characteristics● Building has flat roof withcornices, or several setbacks.● Ornate decorative work inconcrete, terra cotta, caststone or iron.● Large bell tower or clocktower is common.● Simple pattern of windowson all sides.● Floors are concrete slabson steel or concretebeams.● Exterior is stone, terracotta or concrete.Common Structure Types:S2, S5, C2, C3b. 1910-1920(Steel frame with unreinforced masonryinfill that has been seismicallyrehabilitated)d. 1920-1930c. 1920-1930e. 1890-1900FEMA 154 D: Exterior Screening for Seismic System and Age 87

Table D-2Illustrations, Architectural Characteristics, and Age of Commercial Structures (Continued)f. 44 story, 1960s, L-shape on the left;20 story, 1914, with setback onthe rightExamplesg. 1950-19751950-1975Characteristics● Flat roof, typically with nocornice.● Building is square or rectangularfull height, fewersetbacks.● First story and top storycan be taller than otherstories. In some cases thetop story could be shorterthan others.● Exterior finishes metal orglass, pre-cast stone orconcrete.● Floors are concrete slabover steel or concretebeams.Common Structure Types:S1, S2, S4, C1, C2i. 1950-1975h. 1940-1950j. 1950-197588 D: Exterior Screening for Seismic System and Age FEMA 154

Table D-2Illustrations, Architectural Characteristics, and Age of Commercial Structures (Continued)k. Post-1975Examplesl. Post-1975CharacteristicsPost-1975● Flat roof, typically with nocornice.● Building is square or rectangularfor its full height,fewer setbacks.● First story and top storycan be taller than otherstories. (In some cases,though, the top storycould be shorter than others.)● Exterior finishes: metal orglass, pre-cast stone orconcrete, with little ornamentation● Floors are concrete slabsover steel or concretebeams.Common Structure Types:S1, S2, S4, C1, C2m. Post-1975n. Post-1975o. Post-1975is, a building is usually at least as old as it looks.Even when designed to look old, telltale signs ofmodern techniques can usually be seen in the type ofwindows, fixtures, and material used.D.4 Identification of Structural TypeThe most common inspection that will be utilizedwith the RVS procedure will be the exterior or “sidewalk”or “streetside” survey. First, the evaluationshould be as thorough as possible and performed in alogical manner. The street-facing front of the buildingis the starting point and the evaluation begins atthe ground and progressively moves up the exteriorwall to the roof or parapet line. For taller buildings, apair of binoculars is useful. When a thorough inspectionof the street-front elevation has been completed,the procedure is repeated on the next accessible wall.From the exterior, the screener should be able todetermine the approximate age of the building, itsoriginal occupancy, and count the number of stories.FEMA 154 D: Exterior Screening for Seismic System and Age 89

Table D-3Photographs, Architectural Characteristics, and Age of Miscellaneous StructuresExamplesCharacteristicsMixed use (residential with acommercial first floor), placesof assembly, theatres, triangularbuildings, halls, parking structures:●●●Long spansTall first story (for commercialuse) − soft or weak storyAtria or irregular floor-tofloorlayouta. 1920-1930b. 1920-1950c. 1990-2000f. Pre-1930e. 1920-1930; windows createcoupled shear walls.d. 1990-2000; airport terminalg. 1950 − 1965 parkingstructureh. 1920-1930; theater and shops complex, reinforced concrete90 D: Exterior Screening for Seismic System and Age FEMA 154

. Reinforced concrete frame under renovation − demolitionof older facade units.a. Building above is a high-rise steel dual system −moment frame (heavy columns and beams on upperfacade) with bracing around elevator core. Fireproofingis being applied to steel at mid-height (inside theshroud) and precast facade elements are beingattached to frame in lower stories.Figure D-1c. New precast facade units being applied to reinforcedconcrete frame buildings.Photos showing basic construction, in steel-frame buildings and reinforced concrete-framebuildings.With this information, Tables D-4 through D-7 providethe most likely structural system type, based onoriginal occupancy and number of stories. (Thesetables are based on expert judgment and would benefitfrom verification by design professionals andbuilding regulatory personnel familiar with localdesign and construction practices.)In addition to using information on occupancyand number of stories, as provided in Tables D-4through D-7, the following are some locations thatFEMA 154 D: Exterior Screening for Seismic System and Age 91

Table D-4 Most Likely Structural Types for Pre-1930 BuildingsNumber of StoriesOriginal Occupancy 1-2 3 4-6 7-15 15-30 30+Residential W W S5 S5URM URM C3 C3URMCommercial W W S1 S1 S1S4 S4 S2 S2 S2S5 S5 S4 S4 S4C1 C1 S5 S5 S5C2 C2 C1 C1 C1C3 C3 C2 C2 C2URM URM C3 C3 C3URMIndustrial W WS1 S1S2 S2S3 S5S5 C1C1 C2C2 C3C3 URMURMNote: If it is not possible to identify immediately the structural type for a pre-1930 building, the original occupancyand number of stories will provide some guidance. The building will need further inspection for precise identification.Table D-5 Most Likely Structural Types for 1930-1945 BuildingsNumber of StoriesOriginal Occupancy 1-2 3 4-6 7-15 15-30 30+Residential W W S1 S1URM URM S2 S2S5 S5URMCommercial W W S1 S1 S1 S2S1 S1 S2 S2 S2 S5S2 S2 S5 S5 S5S5 S5 C1 C1 C1C1 C1 C2 C2 C2C2 C2 C3 C3 C3C3 C3 RM1RM1 RM1 RM2RM2 RM2 URMURM URMIndustrial S3 S3 C1S5 S5 C2C1 C1 C3C2 C2C3 C3RM1 RM1RM2 RM2URM URMNote: If it is not possible to identify immediately the structural type for a 1930-1945 building, the original occupancyand number of stories will provide some guidance. The building will need further inspection for preciseidentification.92 D: Exterior Screening for Seismic System and Age FEMA 154

Table D-6 Most Likely Structural Types for 1945-1960 BuildingsNumber of StoriesOriginal Occupancy 1-2 3 4-6 7-15 15-30 30+Residential W W S1 S1 S1 S1RM RM S2 S2 S2 S2URM* URM* C1 C1 C1 C1C2 C2 C2 C2RM1,2URM*Commercial W W S1 S1 S1 S1S1 S1 S2 S2 S2 S2S2 S2 C1 C1 C1 C1C1 C1 C2 C2 C2 C2C2 C2 RM1RM1,2 RM1,2 RM2URM* URM* URM*Industrial C1 S1 S1C2 S2 S2PC1 C1 C1RM1 C2 C2RM2 RM1,2 RM1,2URM* URM* URM*Notes: If it is not possible to identify immediately the structural type for a 1945-1960 building, the original occupancyand number of stories will provide some guidance. The building will need further inspection for preciseidentification.*By this period, URM was generally not permitted in California or other high-seismicity locations, so thatonly in the central or eastern U.S. would buildings of this age be URM.Table D-7 Most Likely Structural Types for Post-1960 BuildingsNumber of StoriesOriginal Occupancy 1-2 3 4-6 7-15 15-30 30+Residential W W W S1S1 S1 S1 S2S2 S2 S2 C1C1 C1 C1 C2C2 C2 C2 PC2PC2 PC2 PC2 RM1RM1,2 RM1,2 RM1,2 RM2Commercial W W W S1 S1 S1S1 S1 S1 S2 S2 S2S2 S2 S2 C1 C1 C1C1 C1 C1 C2 C2 C2C2 C2 C2 PC2 PC2PC1 PC1 PC2 RM1PC2 PC2 RM1 RM2RM1,2 RM1,2 RM2Industrial S1 S1 S1 S1 C1S2 S2 S2 S2 C2S3 C1 C1 C1 PC2C1 C2 C2 C2C2 PC1 PC2 PC2PC1 PC2 RM1PC2 RM1 RM2RM1,2 RM2Note: If it is not possible to identify immediately the structural type for a post-1960 building, the original occupancyand number of stories will provide some guidance. The building will need further inspection for precise identification.FEMA 154 D: Exterior Screening for Seismic System and Age 93

the screener can look, without performing destructiveinvestigations, to gain insight into the structure type:1. In newer frame construction the columns areoften exposed on the exterior in the first story. Ifthe columns are covered with a facade material,they are most likely steel columns, indicating asteel frame. If the frames are concrete, they areusually exposed and not covered with a facade.See Figures D-2 and D-3.2. Some structures use a combination of shear wallsin the transverse direction and frames in the longitudinaldirection. This can be seen from theexterior as the shear walls usually extend throughthe exterior longitudinal wall and are exposedthere. This is most common in hotels and otherresidential structures where balconies areincluded. See Figure D-4.3. An inspection of doorways and window framingcan determine wall thickness. When the thicknessexceeds approximately 12 inches, the wall ismost likely unreinforced masonry (URM).Figure D-3Detail of the column facade of Figure D-2.Figure D-2Building with exterior columns coveredwith a facade material.Figure D-4Building with both shear walls (in theshort direction) and frames (in the longdirection).4. If there are vertical joints in the wall, regularlyspaced and extending to the full height, the wallis constructed of concrete, and if three or less storiesin height, the structure type is most likely atilt-up (PC1). See Figure D-5.5. If the building is constructed of brick masonrywithout header courses (horizontal rows of visiblebrick ends), and the wall thickness is approximately8 inches, the structural type is mostlikely reinforced masonry (RM1 or RM2). SeeFigure D-6.6. If the exterior wall shows large concrete blockunits (approximately 8 to 12 inches high and 12to 16 inches in length), either smooth or roughfaced, the structure type may be reinforced concreteblock masonry. See Figure D-7.Because many buildings have been renovated, thescreener should know where to look for clues to theoriginal construction. Most renovations are done forcommercial retail spaces, as businesses like to havean up-to-date image. Most exterior renovations areonly to the front of the building or to walls thatattract attention. Therefore, the original construction94 D: Exterior Screening for Seismic System and Age FEMA 154

Figure D-5Regular, full-height joints in a building’swall indicate a concrete tilt-up.Figure D-7Reinforced masonry building withexterior wall of concrete masonry units, orconcrete blocks.Figure D-6Reinforced masonry wall showing nocourse of header bricks (a row of visiblebrick ends).can often be seen at the sides, or the rear, where peoplegenerally do not look. If the original material iscovered in these areas, it is often just painted orlightly plastered. In this case, the pattern of the oldermaterial can often still be seen.Clues helping identify the original material areapparent if one is looking for them. Two examplesare included here:● Figure D-8 shows a building with a 1970s polishedstone and glass facade. The side of thebuilding indicates that it is a pre-1930 URMbearing-wall structure.● Figure D-9 shows a building facade with typical1960s material. The side was painted. Showingthrough the paint, the horizontal board patterns inthe poured-in-place concrete wall of pre-1940construction could still be seen.Figure D-8A 1970s renovated facade hides a URMbearing-wall structure.D.5 Characteristics of Exposed ConstructionMaterialsAccurate identification of the structural type oftendepends on the ability to recognize the exposed constructionmaterial. The screener should be familiarFEMA 154 D: Exterior Screening for Seismic System and Age 95

Figure D-9A concrete shear-wall structure with a1960s renovated facade.Figure D-10URM wall showing header courses(identified by arrows) and two washerplates indicating wall anchors.with how different materials look on existing buildingsas well as how they have been installed. Briefdescriptions of some common materials are includedhere:● Unreinforced Masonry—Unreinforced masonrywalls, when they are not veneers, are typicallyseveral wythes thick (a wythe is a term denotingthe width of one brick). Therefore, header brickswill be apparent in the exposed surface. Headersare bricks laid with the butt end on the exteriorface, and function to tie wythes of brickstogether. Header courses typically occur everysix or seven courses. (See Figures D-10 andD-11.) Sometimes, URM infill walls will nothave header bricks, and the wythes of brick areheld together only by mortar. Needless to say,URM will look old, and most of the time showwear and weathering. URM may also have a softsand-lime mortar which may be detected byscratching with a knife, unless the masonry hasbeen repointed.●●Reinforced Masonry—Most reinforced brickwalls are constructed using the hollow groutmethod. Two wythes of bricks are laid with ahollow space in between. This space contains thereinforcement steel and is grouted afterward (seeFigure D-12). This method of construction usuallydoes not include header bricks in the wallsurface.Masonry Veneer—Masonry veneers can be ofseveral types, including prefabricated panels,thin brick texture tiles, and a single wythe ofbrick applied onto the structural backing.Figures D-13 shows brick veneer panels. Notethe discontinuity of the brick pattern interruptedby the vertica1 gaps. This indicates that the surfaceis probably a veneer panel. The scupperopening at the top of the wall, probably to let therainwater on the roof to drain, also indicates thatthis is a thin veneer rather than a solid masonryFigure D-11Drawing of two types of masonry pattern showing header bricks (shown with stipples).96 D: Exterior Screening for Seismic System and Age FEMA 154

Figure D-14Hollow clay tile wall with punctured tile.Figure D-12Diagram of common reinforced masonryconstruction. Bricks are left out of thebottom course at intervals to createcleanout holes, then inserted beforegrouting.Figure D-15Sheet metal siding with masonry pattern.Figure D-13●Brick veneer panels.wall. Good places to look for the evidence ofveneer tile are at door or window openings wherethe edge of the tile will usually show.Hollow Clay Tile—The exposed area of a hollowclay tile masonry unit is approximately 6 inchesby 10 inches and often has strip indentations runningthe length of the tile. They are fragile, unreinforced,and without structural value, andusually are used for non-load-bearing walls.●●Figure D-14 shows a typical wall panel whichhas been punctured.False Masonry—Masonry pattern sidings can bemade from sheet metal, plastic, or asphalt material(see Figures D-15 and D-16). These sidingscome in sheets and are attached to a structuralbacking, usually a wood frame. These sidingscan be detected by looking at the edges and bytheir sound when tapped.Cast-in-Place Concrete—Cast-in-place concrete,before the 1940s, will likely show horizontal patternsfrom the wooden formwork. The formworkwas constructed with wood planks, and thereforethe concrete also will often show the wood grainpattern. Since the plank edges were not smooth,FEMA 154 D: Exterior Screening for Seismic System and Age 97

the surface will have horizontal lines approximately4, 6, 8, 10, or 12 inches apart (seeFigure D-17). Newer cast-in-place concretecomes in various finishes. The most economicfinish is that in which the concrete is cast againstplywood formwork, which will reflect the woodgrain appearance of plywood, or against metal orplastic-covered wood forms, which normally donot show a distinctive pattern.Figure D-17Pre-1940 cast-in-place concrete withformwork pattern.Figure D-16Asphalt siding with brick pattern.98 D: Exterior Screening for Seismic System and Age FEMA 154

Appendix ECharacteristics and EarthquakePerformance of RVS Building TypesE.1 IntroductionFor the purpose of the RVS, building structural framingtypes have been categorized into fifteen typeslisted in Section 3.7.1 and shown in Table 3-1. Thisappendix provides additional information about eachof these structural types, including detailed descriptionsof their characteristics, common types of earthquakedamage, and common seismic rehabilitationtechniques.E.2 Wood Frame (W1, W2)E.2.1 CharacteristicsWood frame structures are usually detached residentialdwellings, small apartments, commercial buildingsor one-story industrial structures. They arerarely more than three stories tall, although olderbuildings may be as high as six stories, in rareinstances. (See Figures E-1 and E-2)Figure E-1Single family residence (an example ofthe W1 identifier, light wood-frameresidential and commercial buildings lessthan 5000 square feet).Wood stud walls are typically constructed of 2-inch by 4-inch wood members vertically set about 16inches apart. (See Figures E-3 and E-4). These wallsare braced by plywood or equivalent material, or bydiagonals made of wood or steel. Many detached singlefamily and low-rise multiple family residences inthe United States are of stud wall wood frame construction.Figure E-2Larger wood-framed structure, typicallywith room-width spans (W2, light, woodframebuildings greater than 5000 squarefeet).Post and beam construction, which consists oflarger rectangular (6 inch by 6 inch and larger) orsometimes round wood columns framed togetherwith large wood beams or trusses, is not common andis found mostly in older buildings. These buildingsusually are not residential, but are larger buildingssuch as warehouses, churches and theaters.Timber pole buildings (Figures E-5 and E-6) area less common form of construction found mostly insuburban and rural areas. Generally adequate seismicallywhen first built, they are more often subject towood deterioration due to the exposure of the columns,particularly near the ground surface. Togetherwith an often-found “soft story” in this building type,this deterioration may contribute to unsatisfactoryseismic performance.In the western United States, it can be assumedthat all single detached residential houses (i.e.,houses with rear and sides separate from adjacentstructures) are wood stud frame structures unlessvisual or supplemental information indicates otherwise(in the Southwestern U.S., for example, someresidential homes are constructed of adobe, rammedearth, and other non-wood materials). Many housesthat appear to have brick exterior facades are actuallywood frame with nonstructural brick veneer or brickpatternedsynthetic siding.In the central and eastern United States, brickwalls are usually not veneer. For these houses theFEMA 154 E: Characteristics and Earthquake Performance of RVS Building Types 99

Figure E-3Drawing of wood stud frame construction.brick-work must be examined closely to verify that itis real brick. Second, the thickness of the exteriorwall is estimated by looking at a window or dooropening. If the wall is more than 9 inches from theinterior finish to exterior surface, then it may be abrick wall. Third, if header bricks exist in the brickpattern, then it may be a brick wall. If these featuresall point to a brick wall, the house can be assumed tobe a masonry building, and not a wood frame.In wetter, humid climates it is common to findhomes raised four feet or more above the outsidegrade with this space totally exposed (no foundationwalls). This allows air flow under the house, to minimizedecay and rot problems associated with highhumidity and enclosed spaces. These houses are supportedon wood post and small precast concrete padsor piers. A common name for this construction ispost and pier construction.E.2.2 Typical Earthquake DamageStud wall buildings have performed well in pastearthquakes due to inherent qualities of the structuralsystem and because they are lightweight and lowrise.Cracks in any plaster or stucco may appear, butthese seldom degrade the strength of the building andare classified as nonstructural damage. In fact, this100 E: Characteristics and Earthquake Performance of RVS Building Types FEMA 154

type of damage helps dissipate the earthquakeinducedenergy of the shaking house. The most commontype of structural damage in older buildingsresults from a lack of adequate connection betweenthe house and the foundation. Houses can slide offtheir foundations if they are not properly bolted tothe foundations. This movement (see Figure E-7)results in major damage to the building as well as toplumbing and electrical connections. Overturning ofFigure E-4Stud wall, wood-framed house.Figure E-7House off its foundation, 1983 Coalingaearthquake.Figure E-5Figure E-6Drawing of timber pole framed house.Timber pole framed house.the entire structure is usually not a problem becauseof the low-rise geometry. In many municipalities,modern codes require wood structures to be adequatelybolted to their foundations. However, theyear that this practice was adopted will differ fromcommunity to community and should be checked.Many of the older wood stud frame buildingshave no foundations or have weak foundations ofunreinforced masonry or poorly reinforced concrete.These foundations have poor shear resistance to horizontalseismic forces and can fail.Another problem in older buildings is the stabilityof cripple walls. Cripple walls are short stud wallsbetween the foundation and the first floor level.Often these have no bracing neither in-plane nor outof-planeand thus may collapse when subjected tohorizontal earthquake loading. If the cripple wallscollapse, the house will sustain considerable damageand may collapse. In some older homes, plywoodsheathing nailed to the cripple studs may have beenused to rehabilitate the cripple walls. However, if thesheathing is not nailed adequately to the studs andFEMA 154 E: Characteristics and Earthquake Performance of RVS Building Types 101

Figure E-8foundation sill plate, the cripple walls will still collapse(see Figure E-8).Homes with post and pier perimeter foundations,which are constructed to provide adequate air flowunder the structure to minimize the potential fordecay, have little resistance to earthquake forces.When these buildings are subjected to strong earthquakeground motions, the posts may rotate or slip ofthe piers and the home will settle to the ground. Aswith collapsed cripple walls, this can be very expensivedamage to repair and will result in the homebuilding “red-tagged” per the ATC-20 post-earthquakesafety evaluation procedures (ATC, 1989,1995). See Figure E-9.Figure E-9Failed cripple stud wall, 1992 Big Bearearthquake.Failure of post and pier foundation,Humboldt County.Garages often have a large door opening in thefront wall with little or no bracing in the remainder ofthe wall. This wall has almost no resistance to lateralforces, which is a problem if a heavy load such as asecond story is built on top of the garage. Homesbuilt over garages have sustained damage in pastearthquakes, with many collapses. Therefore thehouse-over-garage configuration, which is foundcommonly in low-rise apartment complexes andsome newer suburban detached dwellings, should beexamined more carefully and perhaps rehabilitated.Unreinforced masonry chimneys present a lifesafetyproblem. They are often inadequately tied tothe house, and therefore fall when strongly shaken.On the other hand, chimneys of reinforced masonrygenerally perform well.Some wood-frame structures, especially olderbuildings in the eastern United States, have masonryveneers that may represent another hazard. Theveneer usually consists of one wythe of brick (awythe is a term denoting the width of one brick)attached to the stud wall. In older buildings, theveneer is either insufficiently attached or has poorquality mortar, which often results in peeling of theveneer during moderate and large earthquakes.Post and beam buildings (not buildings with postand pier foundations) tend to perform well in earthquakes,if adequately braced. However, walls oftendo not have sufficient bracing to resist horizontalmotion and thus they may deform excessively.E.2.3 Common Rehabilitation TechniquesIn recent years, especially as a result of theNorthridge earthquake, emphasis has been placed onaddressing the common problems associated withlight-wood framing. This work has concentratedmainly in the western United States with single-familyresidences.The rehabilitation techniques focus on houseswith continuous perimeter foundations and cripplewalls. The rehabilitation work consists of bolting thehouse to the foundation and providing plywood orother wood sheathing materials to the cripple walls tostrengthen them (see Figure E-10). This is the mostcost-effective rehabilitation work that can be done ona single-family residence.Little work has been done in rehabilitating timberpole buildings or post and pier construction. Intimber pole buildings rehabilitation techniques arefocused on providing resistance to lateral forces bybracing (applying sheathing) to interior walls, creatinga continuous load path to the ground. For homeswith post and pier perimeter foundations, the workhas focused on providing partial foundations andbracing to carry the earthquake loads.102 E: Characteristics and Earthquake Performance of RVS Building Types FEMA 154

ased on their lateral-force-resisting systems.Moment-resisting frames resist lateral loads anddeformations by the bending stiffness of the beamsand columns (there is no diagonal bracing). In concentricbraced frames the diagonal braces are connected,at each end, to the joints where beams andcolumns meet. The lateral forces or loads are resistedby the tensile and compressive strength of the bracing.In eccentric braced frames, the bracing isslightly offset from the main beam-to-column connections,and the short section of beam is expected todeform significantly in bending under major seismicforces, thereby dissipating a considerable portion ofthe energy of the vibrating building. Each type ofsteel frame is discussed below.Figure E-10E.3 Steel Frames (S1, S2)E.3.1Seismic strengthening of a cripple wall,with plywood sheathing.CharacteristicsSteel frame buildings generally may be classified aseither moment-resisting frames or braced frames,Moment-Resisting Steel FrameTypical steel moment-resisting frame structures usuallyhave similar bay widths in both the transverseand longitudinal direction, around 20-30 ft(Figure E-11). The load-bearing frame consists ofbeams and columns distributed throughout the building.The floor diaphragms are usually concrete,Figure E-11Drawing of steel moment-resisting frame building.FEMA 154 E: Characteristics and Earthquake Performance of RVS Building Types 103

sometimes over steel decking. Moment-resistingframe structures built since 1950 often incorporateprefabricated panels hung onto the structural frameas the exterior finish. These panels may be precastconcrete, stone or masonry veneer, metal, glass orplastic.This structural type is used for commercial, institutionaland other public buildings. It is seldom usedfor low-rise residential buildings.Steel frame structures built before 1945 are usuallyclad or infilled with unreinforced masonry suchas bricks, hollow clay tiles and terra cotta tiles andtherefore should be classified as S5 structures (seeSection E.6 for a detailed discussion). Other framebuildings of this period are encased in concrete.Wood or concrete floor diaphragms are common forthese older buildings.Braced Steel FrameBraced steel frame structures (Figures E-12 andE-13) have been built since the late 1800s with similarusage and exterior finish as the steel momentframebuildings. Braced frames are sometimes usedfor long and narrow buildings because of their stiffness.Although these buildings are braced with diagonalmembers, the bracing members usually cannotbe detected from the building exterior.Figure E-13Braced steel frame, with chevron anddiagonal braces. The braces and steelframes are usually covered by finishmaterial after the steel is erected.Figure E-14Chevron bracing in steel building underconstruction.Figure E-12Braced frame configurations.From the building exterior, it is usually difficultto tell the difference between steel moment frames,braced frames, and frames with shear walls. In mostmodern buildings, the bracing or shear walls arelocated in the interior or covered by cladding material.Figure E-14 shows heavy diagonal bracing for ahigh rise building, located at the side walls, whichwill be subsequently covered by finish materials andwill not be apparent. In fact, it is difficult to differentiatesteel frame structures and concrete frame structuresfrom the exterior. Most of the time, thestructural members are clad in finish material. Inolder buildings, steel members can also be encased inconcrete. There are no positive ways of distinguishingthese various frame types except in the two caseslisted below:1. If a building can be determined to be a bracedframe, it is probably a steel structure.104 E: Characteristics and Earthquake Performance of RVS Building Types FEMA 154

2. If exposed steel beams and columns can be seen,then the steel frame structure is apparent. (Especiallyin older structures, a structural framewhich appears to be concrete may actually be asteel frame encased in concrete.)E.3.2 Typical Earthquake DamageSteel frame buildings tend to be generally satisfactoryin their earthquake resistance, because of theirstrength, flexibility and lightness. Collapse in earthquakeshas been very rare, although steel framebuildings did collapse, for example, in the 1985 MexicoCity earthquake. In the United States, these buildingshave performed well, and probably will notcollapse unless subjected to sufficiently severeground shaking. The 1994 Northridge and 1995Kobe earthquakes showed that steel frame buildings(in particular S1 moment-frame) were vulnerable tosevere earthquake damage. Though none of the damagedbuildings collapsed, they were rendered unsafeuntil repaired. The damage took the form of brokenwelded connections between the beams and columns.Cracks in the welds began inside the welds where thebeam flanges were welded to the column flanges.These cracks, in some cases, broke the welds or propagatedinto the column flange, “tearing” the flange.The damage was found in those buildings that experiencedground accelerations of approximately 20% ofgravity (20%g) or greater. Since 1994 Northridge,many cities that experienced large earthquakes in therecent past have instituted an inspection program todetermine if any steel frames were damaged. Sincesteel frames are usually covered with a finish material,it is difficult to find damage to the joints. Theprocess requires removal of the finishes and removalof fireproofing just to see the joint.Possible damage includes the following.1. Nonstructural damage resulting from excessivedeflections in frame structures can occur to elementssuch as interior partitions, equipment, andexterior cladding. Damage to nonstructural elementswas the reason for the discovery of damageto moment frames as a result of the 1994Northridge earthquake.2. Cladding and exterior finish material can fall ifinsufficiently or incorrectly connected.3. Plastic deformation of structural members cancause permanent displacements.4. Pounding with adjacent structures can occur.E.3.3 Common Rehabilitation TechniquesAs a result of the 1994 Northridge earthquake manysteel frame buildings, primarily steel moment frames,have been rehabilitated to address the problems discovered.The process is essentially to redo the connections,ensuring that cracks do not occur in thewelds. There is careful inspection of the welding processand the electrodes during construction. Wherepossible, existing full penetration welds of the beamsto the columns is changed so more fillet welding isFigure E-15Rehabilitation of a concrete parkingstructure using exterior X-braced steelframes.used. This means that less heat is used in the weldingprocess and consequently there is less potential fordamage. Other methods include reducing welding toan absolute minimum by developing bolted connectionsor ensuring that the connection plates will yield(stretch permanently) before the welds will break.One other possibility for rehabilitating momentframes is to convert them to braced frames.The kind of damage discovered was not limitedto moment frames, although they were the mostaffected. Some braced frames were found to havedamage to the brace connections, especially at lowerlevels.Structural types other than steel frames are sometimesrehabilitated using steel frames, as shown forthe concrete structure in Figure E-15. Probably themost common use of steel frames for rehabilitation isin unreinforced masonry bearing-wall buildings(URM). Steel frames are typically used at the storefrontwindows as there is no available horizontalresistance provided by the windows in their plane.Frames can be used throughout the first floor perimeterwhen the floor area needs to be open, as in a restaurant.See Figure E-16.FEMA 154 E: Characteristics and Earthquake Performance of RVS Building Types 105

When a building is encountered with this type ofrehabilitation scheme, the building should be considereda frame type building S1 or S2.E.4 Light Metal (S3)E.4.1 CharacteristicsMost light metal buildings existing today were builtafter 1950 (Figure E-17).They are used for agriculturalstructures, industrial factories, and warehouses.They are typically one story in height, sometimeswithout interior columns, and often enclose a largefloor area. Construction is typically of steel framesspanning the short dimension of the building, resistinglateral forces as moment frames. Forces in thelong direction are usually resisted by diagonal steelrod bracing. These buildings are usually clad withlightweight metal or asbestos-reinforced concretesiding, often corrugated.To identify this construction type, the screenershould look for the following characteristics: Figure E-16 Use of a braced frame to rehabilitate anunreinforced masonry building.Figure E-17Drawing of light metal construction.106 E: Characteristics and Earthquake Performance of RVS Building Types FEMA 154

1. Light metal buildings are typically characterizedby industrial corrugated sheet metal or asbestosreinforcedcement siding. The term, “metalbuilding panels” should not be confused with“corrugated sheet metal siding.” The former areprefabricated cladding units usually used forlarge office buildings. Corrugated sheet metalsiding is thin sheet material usually fastened topurlins, which in turn span between columns. Ifthis sheet cladding is present, the screener shouldexamine closely the fasteners used. If the headsof sheet metal screws can be seen in horizontalrows, the building is most likely a light metalstructure (Figure E-18).Figure E-19Prefabricated metal building (S3, lightmetal building).E.4.2 Typical Earthquake DamageBecause these building are low-rise, lightweight, andconstructed of steel members, they usually performrelatively well in earthquakes. Collapses do not usuallyoccur. Some typical problems are listed below:1. Insufficient capacity of tension braces can lead totheir elongation or failure, and, in turn, buildingdamage.2. Inadequate connection to the foundation canallow the building columns to slide.3. Loss of the cladding can occur.Figure E-18Connection of metal siding to light metalframe with rows of screws (encircled).2. Because the typical structural system consists ofmoment frames in the transverse direction andframes braced with diagonal steel rods in the longitudinaldirection, light metal buildings oftenhave low-pitched roofs without parapets or overhangs(Figure E-19). Most of these buildings areprefabricated, so the buildings tend to be rectangularin plan, without many corners.3. These buildings generally have only a few windows,as it is difficult to detail a window in thesheet metal system.4. The screener should look for signs of a metalbuilding, and should knock on the siding to see ifit sounds hollow. Door openings should beinspected for exposed steel members. If a gap, orlight, can be seen where the siding meets theground, it is certainly light metal or wood frame.For the best indication, an interior inspection willconfirm the structural skeleton, because most ofthese buildings do not have interior finishes.E.5 Steel Frame with Concrete ShearWall (S4)E.5.1 CharacteristicsThe construction of this structural type (Figure E-20)is similar to that of the steel moment-resisting framein that a matrix of steel columns and girders is distributedthroughout the structure. The joints, however,are not designed for moment resistance, and thelateral forces are resisted by concrete shear walls.It is often difficult to differentiate visuallybetween a steel frame with concrete shear walls andone without, because interior shear walls will oftenbe covered by interior finishes and will look likeinterior nonstructural partitions. For the purposes ofan RVS, unless the shear wall is identifiable from theexterior (i.e., a raw concrete finish was part of thearchitectural aesthetic of the building, and was leftexposed), this building cannot be identified accurately.Figure E-21shows a structure with such anexposed shear wall. Figure E-22 is a close-up ofshear wall damage.FEMA 154 E: Characteristics and Earthquake Performance of RVS Building Types 107

Figure E-20Drawing of steel frame with interiorconcrete shear-walls.Figure E-22Close-up of exterior shear wall damageduring a major earthquake.2. Wall construction joints can be weak planes,resulting in wall shear failure at stresses belowexpected capacity.3. Insufficient chord steel lap lengths can lead towall bending failures.E.6 Steel Frame with UnreinforcedMasonry Infill (S5)Figure E-21E.5.2Concrete shear wall on building exterior.Typical Earthquake DamageThe shear walls can be part of the elevator and servicecore, or part of the exterior or interior walls.This type of structure performs as well in earthquakesas other steel buildings. Some typical types ofdamage, other than nonstructural damage and pounding,are:1. Shear cracking and distress can occur aroundopenings in concrete shear walls.E.6.1 CharacteristicsThis construction type (Figures E-23 and E-24) consistsof a steel structural frame and walls “infilled”with unreinforced masonry (URM). In older buildings,the floor diaphragms are often wood. Laterbuildings have reinforced concrete floors. Because ofthe masonry infill, the structure tends to be stiff.Because the steel frame in an older building is coveredby unreinforced masonry for fire protection, it iseasy to confuse this type of building with URM bearing-wallstructures. Further, because the steel columnsare relatively thin, they may be hidden in walls.An apparently solid masonry wall may enclose aseries of steel columns and girders. These infill wallsare usually two or three wythes thick. Therefore,header bricks will sometimes be present and thusmislead the screener into thinking the building is aURM bearing-wall structure, rather than infill. Oftenin these structures the infill and veneer masonry isexposed. Otherwise, masonry may be obscured bycladding in buildings, especially those that haveundergone renovation.When a masonry building is encountered, thescreener should first attempt to determine if themasonry is reinforced, by checking the date of construction,although this is only a rough guide. A108 E: Characteristics and Earthquake Performance of RVS Building Types FEMA 154

Figure E-23Drawing of steel frame with URM infill.clearer indication of a steel frame structure withURM infill is when the building exhibits the characteristicsof a frame structure of type S1 or S2. Onecan assume all frame buildings clad in brick and constructedprior to about 1940 are of this type.Older frame buildings may be of several types—steel frame encased with URM, steel frame encasedwith concrete, and concrete frame. Sometimes olderbuildings have decorative cladding such as terra cottaor stone veneer. Veneers may obscure all evidence ofURM. In that case, the structural type cannot bedetermined. However, if there is evidence that a largeamount of concrete is used in the building (for example,a rear wall constructed of concrete), then it isunlikely that the building has URM infill.When the screener cannot be sure if the buildingis a frame or has bearing walls, two clues may help—the thickness of the walls and the height. Becauseinfill walls are constructed of two or three wythes ofbricks, they should be approximately 9 inches thick(2 wythes). Furthermore, the thickness of the wallwill not increase in the lower stories, because thestructural frame is carrying the load. For buildingsover six stories tall, URM is infill or veneer, becauseURM bearing-wall structures are seldom this talland, if so, they will have extremely thick walls in thelower stories.E.6.2 Typical Earthquake DamageIn major earthquakes, the infill walls may suffer substantialcracking and deterioration from in-plane orout-of-plane deformation, thus reducing the in-planewall stiffness. This in turn puts additional demand onthe frame. Some of the walls may fail while othersremain intact, which may result in torsion or softstory problems.The hazard from falling masonry is significant asthese buildings can be taller than 20 stories. AsFEMA 154 E: Characteristics and Earthquake Performance of RVS Building Types 109

Figure E-24Example of steel frame with URM infillwalls (S5).described below, typical damage results from a varietyof factors.1. Infill walls tend to buckle and fall out-of-planewhen subjected to strong lateral forces. Becauseinfill walls are non-load-bearing, they tend to bethin (around 9") and cannot rely on the additionalshear strength that accompanies vertical compressiveloads.2. Veneer masonry around columns or beams isusually poorly anchored to the structural membersand can disengage and fall.3. Interior infill partitions and other nonstructuralelements can be severely damaged and collapse.4. If stories above the first are infilled, but the firstis not (a soft story), the difference in stiffnesscreates a large demand at the ground floor columns,causing structural damage.5. When the earthquake forces are sufficiently high,the steel frame itself can fail locally. Connectionsbetween members are usually not designed forhigh lateral loads (except in tall buildings) andthis can lead to damage of these connections.Complete collapse has seldom occurred, but cannotbe ruled out.E.6.3 Common Rehabilitation TechniquesRehabilitation techniques for this structural type havefocused on the expected damage. By far the most significantproblem, and that which is addressed in mostrehabilitation schemes, is failure of the infill wall outof its plane. This failure presents a significant lifesafety hazard to individuals on the exterior of thebuilding, especially those who manage to exit thebuilding during the earthquake. To remedy this problem,anchorage connections are developed to tie themasonry infill to the floors and roof of the structure.Another significant problem is the inherent lackof shear strength throughout the building. Some ofthe rehabilitation techniques employed include thefollowing.1. Gunite (with pneumatically placed concrete) theinterior faces of the masonry wall, creating reinforcedconcrete shear elements.2. Rehabilitate the steel frames by providing crossbracing or by fully strengthening the connectionsto create moment frames. In this latter case, theframes are still not sufficient to resist all the lateralforces, and reliance on the infill walls is necessaryto provide adequate strength.For concrete moment frames the rehabilitation techniqueshave been to provide ductile detailing. This isusually done by removing the outside cover of concrete(a couple of inches) exposing the reinforcingties. Additional ties are added with their ends embeddedinto the core of the column. The exterior concreteis then replaced. This process results in a detailthat provides a reasonable amount of ductility but notas much as there would have been had the ductilitybeen provided in the original design.E.7 Concrete Moment-Resisting Frame(C1)E.7.1 CharacteristicsConcrete moment-resisting frame construction consistsof concrete beams and columns that resist bothlateral and vertical loads (see Figure E-25). A fundamentalfactor in the seismic performance of concretemoment-resisting frames is the presence or absenceof ductile detailing. Hence, several construction subtypesfall under this category:a. non-ductile reinforced-concrete frames withunreinforced infill walls,b. non-ductile reinforced-concrete frames withreinforced infill walls,c. non-ductile reinforced-concrete frames, and110 E: Characteristics and Earthquake Performance of RVS Building Types FEMA 154

Figure E-25Drawing of concrete moment-resisting frame building.d. ductile reinforced-concrete frames.Ductile detailing refers to the presence of specialsteel reinforcing within concrete beams and columns.The special reinforcement provides confinement ofthe concrete, permitting good performance in themembers beyond the elastic capacity, primarily inbending. Due to this confinement, disintegration ofthe concrete is delayed, and the concrete retains itsstrength for more cycles of loading (i.e., the ductilityis increased). See Figure E-26 for a dramatic exampleof ductility in concrete.Ductile detailing (Figure E-27) has been practicedin high-seismicity areas since 1967, when ductilityrequirements were first introduced into theUniform Building Code (the adoption and enforcementof ductility requirements in a given jurisdictionFigure E-26Extreme example of ductility in concrete,1994 Northridge earthquake.FEMA 154 E: Characteristics and Earthquake Performance of RVS Building Types 111

Figure E-27Example of ductile reinforced concretecolumn, 1994 Northridge earthquake;horizontal ties would need to be closerfor greater demands. Figure E-28 Concrete moment-resisting framemay be later, however). Prior to that time, nonductileor ordinary concrete moment-resisting frames werethe norm (and still are, for moderate seismic areas).In high-seismicity areas additional tie reinforcingwas required following the 1971 San Fernando earthquakeand appeared in the Uniform Building Code in1976.In many low-seismicity areas of the UnitedStates, non-ductile concrete frames of type (a), (b),and (c) continue to be built. This group includes largemultistory commercial, institutional, and residentialbuildings constructed using flat slab frames, waffleslab frames, and the standard beam-and-columnframes. These structures generally are more massivethan steel-frame buildings, are under-reinforced (i.e.,have insufficient reinforcing steel embedded in theconcrete) and display low ductility.This building type is difficult to differentiatefrom steel moment-resisting frames unless the structuralconcrete has been left relatively exposed (seeFigure E-28). Although a steel frame may be encasedin concrete and appear to be a concrete frame, this isseldom the case for modern buildings (post 1940s).For the purpose of the RVS procedures, it can beassumed that all exposed concrete frames are concreteand not steel frames.building (C1) with exposed concrete,deep beams, wide columns (and witharchitectural window framing).E.7.2 Typical Earthquake DamageUnder high amplitude cyclic loading, lack of confinementwill result in rapid disintegration of nonductileconcrete members, with ensuing brittle failureand possible building collapse (see Figure E-29).Causes and types of damage include:1. Excessive tie spacing in columns can lead to alack of concrete confinement and shear failure.2. Placement of inadequate rebar splices all at thesame location in a column can lead to columnfailure.3. Insufficient shear strength in columns can lead toshear failure prior to the full development ofmoment hinge capacity.4. Insufficient shear tie anchorage can prevent thecolumn from developing its full shear capacity.5. Lack of continuous beam reinforcement canresult in unexpected hinge formation during loadreversal.112 E: Characteristics and Earthquake Performance of RVS Building Types FEMA 154

Figure E-29Locations of failures at beam-to-column joints in nonductile frames, 1994 Northridge earthquake.6. Inadequate reinforcing of beam-column joints orthe positioning of beam bar splices at columnscan lead to failures.7. The relatively low stiffness of the frame can leadto substantial nonstructural damage.8. Pounding damage with adjacent buildings canoccur.E.7.3 Common Rehabilitation TechniquesRehabilitation techniques for reinforced concreteframe buildings depend on the extent to which theframe meets ductility requirements. The costs associatedwith the upgrading an existing, conventionalbeam-column framing system to meet the minimumstandards for ductility are high and this approach isusually not cost-effective. The most practical andcost-effective solution is to add a system of shearwalls or braced frames to provide the required seismicresistance (ATC, 1992).E.8 Concrete Shear Wall (C2)E.8.1 CharacteristicsThis category consists of buildings with a perimeterconcrete bearing-wall structural system or framestructures with shear walls (Figure E-30). The structure,including the usual concrete floor diaphragms,is typically cast in place. Before the 1940s, bearingwallsystems were used in schools, churches, andindustrial buildings. Concrete shear-wall buildingsconstructed since the early 1950s are institutional,commercial, and residential buildings, ranging fromone to more than thirty stories. Frame buildings withshear walls tend to be commercial and industrial. Acommon example of the latter type is a warehousewith interior frames and perimeter concrete walls.Residential buildings of this type are often mid-risetowers. The shear walls in these newer buildings canbe located along the perimeter, as interior partitions,or around the service core.Frame structures with interior shear walls are difficultto identify positively. Where the building isclearly a box-like bearing-wall structure it is probablya shear-wall structure. Concrete shear wall buildingsare usually cast in place. The screener shouldlook for signs of cast-in-place concrete. In concretebearing-wall structures, the wall thickness rangesfrom 6 to 10 inches and is thin in comparison to thatof masonry bearing-wall structures.FEMA 154 E: Characteristics and Earthquake Performance of RVS Building Types 113

Figure E-30Drawing of concrete shear-wall building.E.8.2Typical Types of Earthquake DamageThis building type generally performs better thanconcrete frame buildings. The buildings are heavycompared with steel frame buildings, but they arealso stiff due to the presence of the shear walls. Damagecommonly observed in taller buildings is causedby vertical discontinuities, pounding, and irregularconfiguration. Other damage specific to this buildingtype includes the following.1. During large seismic events, shear cracking anddistress can occur around openings in concreteshear walls and in spandrel beams and linkbeams between shear walls (See Figures E-31and E-32.)2. Shear failure can occur at wall constructionjoints usually at a load level below the expectedcapacity.3. Bending failures can result from insufficient verticalchord steel and insufficient lap lengths atthe ends of the walls.E.8.3 Common RehabilitationReinforced concrete shear-wall buildings can berehabilitated in a variety of ways. Techniquesinclude: (1) reinforcing existing walls in shear byapplying a layer of shotcrete or poured concrete; (2)where feasible, filling existing window or door openingswith concrete to add shear strength and eliminatecritical bending stresses at the edge of openings;and (3) reinforcing narrow overstressed shear panelsin in-plane bending by adding reinforced boundaryelements (ATC, 1992).E.9 Concrete Frame with UnreinforcedMasonry Infill (C3)E.9.1 CharacteristicsThese buildings (Figures E-33 and E-34) have been,and continue to be, built in regions where unreinforcedmasonry (URM) has not been eliminated bycode. These buildings were generally built before1940 in high-seismicity regions and may continue tobe built in other regions.The first step in identification is to determine ifthe structure is old enough to contain URM. In contrastto steel frames with URM infill, concrete frameswith URM infill usually show clear evidence of theconcrete frames. This is particularly true for industrialbuildings and can usually be observed at the sideor rear of commercial buildings. The concrete col-114 E: Characteristics and Earthquake Performance of RVS Building Types FEMA 154

Figure E-33Concrete frame with URM infill.Figure E-31Tall concrete shear-wall building: wallsconnected by damaged spandrel beams.Figure E-32Shear-wall damage, 1989 Loma Prietaearthquake.umns and beams are relatively large and are usuallynot covered by masonry but left exposed.A case in which URM infill cannot be readilyidentified is the commercial building with large windowson all sides; these buildings may have interiorURM partitions. Another difficult case occurs whenthe exterior walls are covered by decorative tile orFigure E-34Blow-up (lower photo) of distant view ofC3 building (upper photo) showingconcrete frame with URM infill (left wall),and face brick (right wall).FEMA 154 E: Characteristics and Earthquake Performance of RVS Building Types 115

stone veneer. The infill material can be URM or athin concrete infill.E.9.2 Typical Earthquake DamageThe hazards of these buildings, which in the westernUnited States are often older, are similar to and perhapsmore severe than those of the newer concreteframes. Where URM infill is present, a falling hazardexists. The failure mechanisms of URM infill in aconcrete frame are generally the same as URM infillin a steel frame.E.9.3 Common Rehabilitation TechniquesRehabilitation of unreinforced masonry infill in aconcrete frame is identical to that of the URM infillin a steel frame. See Section E.6.3. Anchorage of thewall panels for out-of-plane forces is the key component,followed by providing sufficient shear strengthin the building.E.10 Tilt-up Structures (PC1)E.10.1 CharacteristicsIn traditional tilt-up buildings (Figures E-35 throughE-37), concrete wall panels are cast on the groundFigure E-35Drawing of tilt-up construction typical of the western United States. Tilt-up construction in the easternUnited States may incorporate a steel frame.116 E: Characteristics and Earthquake Performance of RVS Building Types FEMA 154

flat roofs built after 1950 are tilt-ups unless supplementaryinformation indicates otherwise.Figure E-36 Tilt-up industrial building, 1970s.E.10.2 Typical Earthquake DamageBefore 1973 in the western United States, many tiltupbuildings did not have sufficiently strong connectionsor anchors between the walls and the roof andfloor diaphragms. The anchorage typically was nothingmore than the nailing of the plywood roof sheathingto the wood ledgers supporting the framing.During an earthquake, the weak anchorage brokethe ledgers, resulting in the panels falling and thesupported framing to collapse. When mechanicalanchors were used they pulled out of the walls orsplit the wood members to which they were attached,causing the floors or roofs to collapse. SeeFigures E-38 and E-39. The connections between theconcrete panels are also vulnerable to failure. Withoutthese connections, the building loses much of itslateral-force-resisting capacity. For these reasons,many tilt-up buildings were damaged in the 1971 SanFigure E-37Tilt-up industrial building, mid- to late1980s.and then tilted upward into their final positions. Morerecently, wall panels are fabricated off-site andtrucked to the site.Tilt-up buildings are an inexpensive form of lightindustrial and commercial construction and havebecome increasingly popular in the western and centralUnited States since the 1940s. They are typicallyone and sometimes two stories high and basicallyhave a simple rectangular plan. The walls are the lateral-force-resistingsystem. The roof can be a plywooddiaphragm carried on wood purlins and gluelaminated(glulam) wood beams or a light steel deckand joist system, supported in the interior of thebuilding on steel pipe columns. The wall panels areattached to concrete cast-in-place pilasters or to steelcolumns, or the joint is simply closed with a laterconcrete pour. These joints are typically spaced about20 feet apart.The major defect in existing tilt-ups is a lack ofpositive anchorage between wall and diaphragm,which has been corrected since about 1973 in thewestern United States.In the western United States, it can be assumedthat all one-story concrete industrial warehouses withFigure E-38Figure E-39Tilt-up construction anchorage failure.Result of failure of the roof beamanchorage to the wall in tilt-up building.FEMA 154 E: Characteristics and Earthquake Performance of RVS Building Types 117

Fernando, California, earthquake. Since 1973, tiltupconstruction practices have changed in Californiaand other high-seismicity regions, requiring positivewall-diaphragm connection. (Such requirements maynot have yet been made in other regions of the country.)However, a large number of these older, pre-1970s-vintage tilt-up buildings still exist and havenot been rehabilitated to correct this wall-anchordefect. Damage to these buildings was observedagain in the 1987 Whittier, California, earthquake,1989 Loma Prieta, California earthquake, and the1994 Northridge, California, earthquake. Thesebuildings are a prime source of seismic hazard.In areas of low or moderate seismicity, inadequatewall anchor details continue to be used. Severeground shaking in such an area may produce majordamage in tilt-up buildings.E.10.3 Common Rehabilitation TechniquesThe rehabilitation of tilt-up buildings is relativelyeasy and inexpensive. The most common form ofrehabilitation is to provide a positive anchorage connectionat the roof and wall intersection. This is usuallydone by using pre-fabricated metal hardwareattached to the framing member and to a bolt that isinstalled through the wall. On the outside of the walla large washer plate is used. See Figure E-40 forexamples of new anchors.Accompanying the anchorage rehabilitation isthe addition of ties across the building to develop theanchorage forces from the wall panels fully into thediaphragm. This is accomplished by interconnectingframing members from one side of the building to theother, and then increasing the connections of the diaphragm(usually wood) to develop the additionalforces.E.11 Precast Concrete Frame (PC2)E.11.1 CharacteristicsPrecast concrete frame construction, first developedin the 1930s, was not widely used until the 1960s.The precast frame (Figure E-41) is essentially a postand beam system in concrete where columns, beamsand slabs are prefabricated and assembled on site.Various types of members are used. Vertical-loadcarryingelements may be Ts, cross shapes, or archesand are often more than one story in height. Beamsare often Ts and double Ts, or rectangular sections.Prestressing of the members, including pretensioningand post-tensioning, is often employed. The identificationof this structure type cannot rely solely onconstruction date, although most precast concreteFigure E-40Newly installed anchorage of roof beamto wall in tilt-up building.frame structures were constructed after 1960. Sometypical characteristics are the following.1. Precast concrete, in general, is of a higher qualityand precision compared to cast-in-place concrete.It is also available in a greater range of texturesand finishes. Many newer concrete andsteel buildings have precast concrete panels andcolumn covers as an exterior finish (SeeFigure E-42). Thus, the presence of precast concretedoes not necessarily mean that it is a precastconcrete frame.2. Precast concrete frames are, in essence, post andbeam construction in concrete. Therefore, whena concrete structure displays the features of apost-and-beam system, it is most likely that it is aprecast concrete frame. It is usually not economicalfor a conventional cast-in-place concreteframe to look like a post-and-beam system. Featuresof a precast concrete post-and-beam systeminclude:a. exposed ends of beams and girders that projectbeyond their supports or project away from thebuilding surface,118 E: Characteristics and Earthquake Performance of RVS Building Types FEMA 154

Figure E-41Drawing of precast concrete frame building.b. the absence of small joists, andc. beams sitting on top of girders rather than meetingat a monolithic joint (see Figure E-43)The presence of precast structural components is usuallya good indication of this system, although thesecomponents are also used in mixed construction. Precaststructural components come in a variety ofshapes and sizes. The most common types are sometimesdifficult to detect from the street. Less commonbut more obvious examples include the following.a. Ts or double Ts—These are deep beams with thinwebs and flanges and with large span capacities.(Figure E-44 shows one end of a double-T beamas it is lowered onto its seat.)b. Cross or T-shaped units of partial columns andbeams — These are structural units for constructingmoment-resisting frames. They are usuallyjoined together by field welding of steel connectorscast into the concrete. Joints should beclearly visible at the mid-span of the beams orthe mid-height of the columns. See Figure E-45.c. Precast arches—Precast arches and pedestals arepopular in the architecture of these buildings.d. Column—When a column displays a precast finishwithout an indication that it has a cover (i.e.,FEMA 154 E: Characteristics and Earthquake Performance of RVS Building Types 119

Figure E-42Typical precast column cover on a steelor concrete moment frame.Figure E-45Precast structural cross; installation jointsare at sections where bending isminimum during high seismic demand.Figure E-43Figure E-44Exposed precast double-T sections andoverlapping beams are indicative ofprecast frames.Example of precast double-T sectionduring installation.no vertical seam can be found), the column islikely to be a precast structural column.It is possible that a precast concrete frame may notshow any of the above features, however.E.11.2 Typical Earthquake DamageThe earthquake performance of this structural typevaries widely and is sometimes poor. This type ofbuilding can perform well if the detailing used toconnect the structural elements have sufficientstrength and ductility (toughness). Because structuresof this type often employ cast-in-place concrete orreinforced masonry (brick or block) shear walls forlateral-load resistance, they experience the sametypes of damage as other shear-wall building types.Some of the problem areas specific to precast framesare listed below.1. Poorly designed connections between prefabricatedelements can fail.2. Accumulated stresses can result due to shrinkageand creep and due to stresses incurred in transportation.3. Loss of vertical support can occur due to inadequatebearing area and insufficient connectionbetween floor elements and columns.4. Corrosion of the metal connectors between prefabricatedelements can occur.E.11.3 Common Rehabilitation TechniquesSeismic rehabilitation techniques for precast concreteframe buildings are varied, depending on the elementsbeing strengthened. Inadequate shear capacityof floor diaphragms can be addressed by adding reinforcedconcrete topping to an untopped system when120 E: Characteristics and Earthquake Performance of RVS Building Types FEMA 154

possible, or adding new shear walls to reduce theseismic shear forces in the diaphragm. Corbels withinadequate vertical shear or bending strength can bestrengthened by adding epoxied horizontal sheardowels through the corbel and into the column.Alternatively, vertical shear capacity can beincreased by adding a structural steel bolster underthe corbel, bolted to the column, or a new steel columnor reinforced concrete column can be added(ATC, 1992).E.12 Reinforced Masonry (RM1 andRM2)E.12.1 CharacteristicsReinforced masonry buildings are mostly low-risestructures with perimeter bearing walls, often withwood diaphragms (RM1 buildings) although precastconcrete is sometimes used (RM2 buildings). Floorand roof assemblies usually consist of timber joistsand beams, glued-laminated beams, or light steeljoists. The bearing walls consist of grouted and reinforcedhollow or solid masonry units. Interior supports,if any, are often wood or steel columns, woodstud frames, or masonry walls. Occupancy variesfrom small commercial buildings to residential andindustrial buildings. Generally, they are less than fivestories in height although many taller masonry buildingsexist. Reinforced masonry structures are usuallybasically rectangular structures (See Figure E-46).Figure E-46Modern reinforced brick masonry.To identify reinforced masonry, one must determineseparately if the building is masonry and if it isreinforced. To obtain information on how to recognizea masonry structure, see Appendix D, whichdescribes the characteristics of construction materials.The best way of assessing the reinforcement conditionis to compare the date of construction with thedate of code requirement for the reinforcement ofmasonry in the local jurisdiction.The screener also needs to determine if the buildingis veneered with masonry or is a masonry building.Wood siding is seldom applied over masonry. Ifthe front facade appears to be reinforced masonrywhereas the side has wood siding, it is probably awood frame that has undergone facade renovation.The back of the building should be checked for signsof the original construction type.If it can be determined that the bearing walls areconstructed of concrete blocks, they may be reinforced.Load-bearing structures using these blocksare probably reinforced if the local code required it.Concrete blocks come in a variety of sizes and textures.The most common size is 8 inches wide by 16inches long by 8 inches high. Their presence is obviousif the concrete blocks are left as the finish surface.E.12.2 Typical Earthquake DamageReinforced masonry buildings can perform well inmoderate earthquakes if they are adequately reinforcedand grouted, and if sufficient diaphragmanchorage exists. A major problem is control of theworkmanship during construction. Poor constructionpractice can result in ungrouted and unreinforcedwalls. Even where construction practice is adequate,insufficient reinforcement in the design can beresponsible for heavy damage of the walls. The lackof positive connection of the floor and roof diaphragmsto the wall is also a problem.E.12.3 Common Rehabilitation TechniquesTechniques for seismic rehabilitation of reinforcedmasonry bearing wall buildings are varied, dependingon the element being rehabilitated. Techniquesfor rehabilitating masonry walls include: (1) applyinga layer of concrete or shotcrete to the existing walls;(2) adding vertical reinforcing and grouting intoungrouted block walls; and (3) filling in large or criticalopenings with reinforced concrete or masonrydowelled to the surrounding wall. Wood or steeldeck diaphragms in RM1 buildings can be rehabilitatedby adding an additional layer of plywood tostrengthen and stiffen an existing wood diaphragm,by shear welding between sections of an existingsteel deck or adding flat sheet steel reinforcement, orby adding additional vertical elements (for example,shear walls or braced frames) to decrease diaphragmspans and stresses. Precast floor diaphragms in RM2buildings can be strengthen by adding a layer of concretetopping reinforced with mesh (if the supportingstructure has the capacity to carry the additional verticaldead load), or by adding new shear walls toreduce the diaphragm span (ATC, 1992).FEMA 154 E: Characteristics and Earthquake Performance of RVS Building Types 121

Figure E-47Drawing of unreinforced masonry bearing-wall building, 2-story.E.13 Unreinforced Masonry (URM)E.13.1 CharacteristicsMost unreinforced masonry (URM) bearing-wallstructures in the western United States (Figures E-47through E-51) were built before 1934, although thisconstruction type was permitted in some jurisdictionshaving moderate or high seismicity until the late1940s or early 1950s (in some jurisdictions URMmay still be a common type of construction, eventoday). These buildings usually range from one to sixstories in height and function as commercial, residential,or industrial buildings. The construction variesaccording to the type of use, although wood floor androof diaphragms are common. Smaller commercialand residential buildings usually have light woodfloor joists and roof joists supported on the typicalperimeter URM wall and interior, wood, load-bearingpartitions. Larger buildings, such as industrialwarehouses, have heavier floors and interior columns,usually of wood. The bearing walls of theseindustrial buildings tend to be thick, often as much as24 inches or more at the base. Wall thickness of residential,commercial, and office buildings range from9 inches at upper floors to 18 inches a lower floors.The first step in identifying buildings of this typeis to determine if the structure has bearing walls. Second,the screener should determine the approximateage of the building. Some indications of unreinforcedmasonry are listed below.1. Weak mortar was used to bond the masonry unitstogether in much of the early unreinforced122 E: Characteristics and Earthquake Performance of RVS Building Types FEMA 154

Figure E-48Drawing of unreinforced masonry bearing-wall building, 4-story.masonry construction in the United States. As thepoor earthquake performance of this mortar typebecame known in the 1930s, and as cement mortarbecame available, this weaker mortar was notused and thus is not found in more recentmasonry buildings. If this soft mortar is present,it is probably URM. Soft mortar can be scratchedwith a hard instrument such as a penknife, screwdriver,or a coin. This scratch testing, if permitted,should be done in a wall area where theoriginal structural material is exposed, such asthe sides or back of a building. Newer masonrymay be used in renovations and it may look verymuch like the old. Older mortar joints can also berepointed (i.e., regular maintenance of themasonry mortar), or repaired with newer mortarduring renovation. The original construction mayalso have used a high-quality mortar. Thus, evenif the existence of soft mortar cannot be detected,it may still be URM.2. An architectural characteristic of older brickbearing-wall structures is the arch and flat archFEMA 154 E: Characteristics and Earthquake Performance of RVS Building Types 123

Figure E-49Drawing of unreinforced masonry bearing-wall building, 6-story.Figure E-50 East coast URM bearing-wall building. Figure E-51 West coast URM bearing-wall building.124 E: Characteristics and Earthquake Performance of RVS Building Types FEMA 154

Figure E-52Drawings of typical window head features in URM bearing-wall buildings.window heads (see Figure E-52). These arrangementsof masonry units function as a header tocarry the load above the opening to either side.Although masonry-veneered wood-frame structuresmay have these features, they are muchmore widely used in URM bearing-wall structures,as they were the most economical methodof spanning over a window opening at the timeof construction. Other methods of spanning arealso used, including steel and stone lintels, butthese methods are generally more costly and usuallyemployed in the front facade only.3. Some structures of this type will have anchorplates visible at the floor and roof lines, approximately6-10 feet on center around the perimeterof the building. Anchor plates are usually squareor diamond-shaped steel plates approximately 6inches by 6 inches, with a bolt and nut at the center.Their presence indicates anchor ties havebeen placed to tie the walls to the floors and roof.These are either from the original construction orfrom rehabilitation under local ordinances.Unless the anchors are 6 feet on center or less,they are not considered effective in earthquakes.If they are closely spaced, and appear to berecently installed, it indicates that the buildinghas been rehabilitated. In either case, when theseanchors are present all around the building, theoriginal construction is URM bearing wall.4. When a building has many exterior solid wallsconstructed from hollow clay tile, and no columnsof another material can be detected, it isprobably not a URM bearing wall but probably awood or metal frame structure with URM infill.5. One way to distinguish a reinforced masonrybuilding from an unreinforced masonry buildingis to examine the brick pattern closely. Reinforcedmasonry usually does not show headerbricks in the wall surface.FEMA 154 E: Characteristics and Earthquake Performance of RVS Building Types 125

If a building does not display the above features, or ifthe exterior is covered by other finish material, thebuilding may still be URM.E.13.2 Typical Earthquake DamageUnreinforced masonry structures are recognized asthe most hazardous structural type. They have beenobserved to fail in many modes during past earthquakes.Typical problems include the following.1. Insufficient Anchorage—Because the walls, parapets,and cornices are not positively anchored tothe floors, they tend to fall out. The collapse ofbearing walls can lead to major building collapses.Some of these buildings have anchors as apart of the original construction or as a rehabilitation.These older anchors exhibit questionableperformance. (See Figure E-53 for parapet damage.)accompanying translations in the direction of theopen front walls of buildings, due to a lack of inplanestiffness in these open fronts. Becausethere is little resistance in the masonry walls forout-of-plane loading, the walls allow large diaphragmdisplacements and cause the failure ofthe walls out of their plane. Large drifts occurringat the roof line can cause a masonry wall tooverturn and collapse under its own weight.3. Low Shear Resistance—The mortar used in theseolder buildings was often made of lime and sand,with little or no cement, and had very little shearstrength. The bearing walls will be heavily damagedand collapse under large loads. (SeeFigure E-54)Figure E-54Damaged URM building,1992 Big Bear earthquake.4. Slender Walls —Some of these buildings havetall story heights and thin walls. This condition,especially in non-load-bearing walls, will resultin buckling out-of-plane under severe lateralload. Failure of a non-load-bearing wall representsa falling hazard, whereas the collapse of aload-bearing wall will lead to partial or total collapseof the structure.Figure E-53Parapet failure leaving an uneven roofline, due to inadequate anchorage, 1989Loma Prieta earthquake.2. Excessive Diaphragm Deflection—Becausemost of the floor diaphragms are constructed offinished wood flooring placed over ¾”-thickwood sheathing, they tend to be stiff comparedwith other types of wood diaphragms. This stiffnessresults in rotations about a vertical axis,E.13.3 Common Rehabilitation TechniquesOver the last 10 years or more, jurisdictions in Californiahave required that unreinforced masonry bearing-wallbuildings be rehabilitated or demolished. Tominimize the economical impact on owners of havingto rehabilitate their buildings, many jurisdictionsimplemented phased programs such that the criticalitems were dealt with first. The following are the keyelements included in a typical rehabilitation program.1. Roof and floor diaphragms are connected to thewalls for both anchorage forces (out of the planeof the wall) and shear forces (in the plane of the126 E: Characteristics and Earthquake Performance of RVS Building Types FEMA 154

wall). Anchorage connections are placed at 6 feetspacing or less, depending on the force requirements.Shear connections are usually placed ataround 2 feet center to center. Anchors consist ofbolts installed through the wall, with 6-inchsquarewasher plates, and connected to hardwareattached to the wood framing. Shear connectionsusually are bolts embedded in the masonry wallsin oversized holes filled with either a non-shrinkgrout or an epoxy adhesive. See Figure E-55.2. In cases when the height to thickness ratio of thewalls exceeds the limits of stability, rehabilitationconsists of reducing the spans of the wall toa level that their thickness can support. Parapetrehabilitation consists of reducing the parapet towhat is required for fire safety and then bracingfrom the top to the roof.3. If the building has an open storefront in the firststory, resulting in a soft story, part of the storefrontis enclosed with new masonry or a steelframe is provided there, with new foundations.4. Walls are rehabilitated by either closing openingswith reinforced masonry or with reinforcedgunite.Figure E-55Upper: Two existing anchors above threenew wall anchors at floor line usingdecorative washer plates. Lower:Rehabilitation techniques include closelyspaced anchors at floor and roof levels.FEMA 154 E: Characteristics and Earthquake Performance of RVS Building Types 127

Appendix FEarthquakes and How BuildingsResist ThemF.1 The Nature of EarthquakesIn a global sense, earthquakes result from motionbetween plates comprising the earth’s crust (seeFigure F-1). These plates are driven by the convectivemotion of the material in the earth’s mantlebetween the core and the crust, which in turn isdriven by heat generated at the earth’s core. Just as ina heated pot of water, heat from the earth’s corecauses material to rise to the earth’s surface. Forcesbetween the rising material and the earth’s crustalplates cause the plates to move. The resulting relativemotions of the plates are associated with the generationof earthquakes. Where the plates spread apart,molten material fills the void. An example is theridge on the ocean floor, at the middle of the AtlanticOcean. This material quickly cools and, over millionsof years, is driven by newer, viscous, fluid materialacross the ocean floor.These large pieces of the earth’s surface, termedtectonic plates, move very slowly and irregularly.Forces build up for decades, centuries, or millennia atthe interfaces (or faults) between plates, until a largereleasing movement suddenly occurs. This sudden,violent motion produces the nearby shaking that isfelt as an earthquake. Strong shaking produces stronghorizontal forces on structures, which can causedirect damage to buildings, bridges, and other manmadestructures as well as triggering fires, landslides,road damage, tidal waves (tsunamis) and other damagingphenomena.Figure F-1The separate tectonic plates comprising the earth’s crust superimposed on a map of the world.FEMA 154 F: Earthquakes and How Buildings Resist Them 129

A fault is like a “tear” in the earth’s crust and itsfault surface may be from one to over one hundredmiles deep. In some cases, faults are the physicalexpression of the boundary between adjacent tectonicplates and thus are hundreds of miles long. In addition,there are shorter faults, parallel to, or branchingout from, a main fault zone. Generally, the longer afault, the larger magnitude earthquake it can generate.Beyond the main tectonic plates, there are manysmaller sub-plates, “platelets” and simple blocks ofcrust which can move or shift due to the “jostling” oftheir neighbors and the major plates. The knownexistence of these many sub-plates implies thatsmaller but still damaging earthquakes are possiblealmost anywhere.With the present understanding of the earthquakegenerating mechanism, the times, sizes and locationsof earthquakes cannot be reliably predicted. Generally,earthquakes will be concentrated in the vicinityof faults, and certain faults are more likely than othersto produce a large event, but the earthquake generatingprocess is not understood well enough topredict the exact time of earthquake occurrence.Therefore, communities must be prepared for anearthquake to occur at any time.Four major factors can affect the severity ofground shaking and thus potential damage at a site.These are the magnitude of the earthquake, the typeof earthquake, the distance from the source of theearthquake to the site, and the hardness or softness ofthe rock or soil at the site. Larger earthquakes willshake longer and harder, and thus cause more damage.Experience has shown that the ground motioncan be felt for several seconds to a minute or longer.In preparing for earthquakes, both horizontal (side toside) and vertical shaking must be considered.There are many ways to describe the size andseverity of an earthquake and associated groundshaking. Perhaps the most familiar are earthquakemagnitude and Modified Mercalli Intensity (MMI,often simply termed “intensity”). Earthquake magnitudeis technically known as the Richter magnitude, anumerical description of the maximum amplitude ofground movement measured by a seismograph(adjusted to a standard setting). On the Richter scale,the largest recorded earthquakes have had magnitudesof about 8.5. It is a logarithmic scale, and a unitincrease in magnitude corresponds to a ten-foldincrease in the adjusted ground displacement amplitude,and to approximately a thirty-fold increase intotal potential strain energy released by the earthquake.Modified Mercalli Intensity (MMI) is a subjectivescale defining the level of shaking at specificsites on a scale of I to XII. (MMI is expressed inRoman numerals, to connote its approximate nature.)For example, slight shaking that causes few instancesof fallen plaster or cracks in chimneys constitutesMMI VI. It is difficult to find a reliable precise relationshipbetween magnitude, which is a descriptionof the earthquake’s total energy level, and intensity,which is a subjective description of the level of shakingof the earthquake at specific sites, because shakingintensity can vary with earthquake magnitude,soil type, and distance from the event.The following analogy may be worth remembering:earthquake magnitude and intensity are similarto a light bulb and the light it emits. A particular lightbulb has only one energy level, or wattage (e.g., 100watts, analogous to an earthquake’s magnitude). Nearthe light bulb, the light intensity is very bright (perhaps100 foot-candles, analogous to MMI IX), whilefarther away the intensity decreases (e.g., 10 footcandles,MMI V). A particular earthquake has onlyone magnitude value, whereas it has intensity valuesthat differ throughout the surrounding land.MMI is a subjective measure of seismic intensityat a site, and cannot be measured using a scientificinstrument. Rather, MMI is estimated by scientistsand engineers based on observations, such as thedegree of disturbance to the ground, the degree ofdamage to typical buildings and the behavior of people.A more objective measure of seismic shaking ata site, which can be measured by instruments, is asimple structure’s acceleration in response to theground motion. In this Handbook, the level of groundshaking is described by the spectral response acceleration.F.2 Seismicity of the United StatesMaps showing the locations of earthquake epicentersover a specified time period are often used to characterizethe seismicity of given regions. Figures F-2,F-3, and F-4 show the locations of earthquake epicenters4 in the conterminous United States, Alaska,and Hawaii, respectively, recorded during the timeperiod, 1977-1997. It is evident from Figures F-2through F-4 that some parts of the country have experiencedmore earthquakes than others. The boundarybetween the North American and Pacific tectonicplates lies along the west coast of the United Statesand south of Alaska. The San Andreas fault in Californiaand the Aleutian Trench off the coast ofAlaska are part of this boundary. These active seismiczones have generated earthquakes with Richter4 An epicenter is defined as the point on the earth’ssurface beneath which the rupture process for agiven earthquake commenced.130 F: Earthquakes and How Buildings Resist Them FEMA 154

Figure F-2Seismicity of the conterminous United States 1977 − 1997 (from the website at http://neic.usgs.gov/neis/general/seismicity/us.html). This reproduction shows earthquake locations without regard tomagnitude or depth. The San Andreas fault and other plate boundaries are indicated with white lines.magnitudes greater than 8. There are many othersmaller fault zones throughout the western UnitedStates that are also participating intermittently inreleasing the stresses and strains that are built up asthe tectonic plates try to move past one another.Because earthquakes always occur along faults, theseismic hazard will be greater for those populationcenters close to active fault zones.In California the earthquake hazard is so significantthat special study zones have been created by thelegislature, and named Alquist-Priola Special StudyZones. These zones cover the larger known faultsand require special geotechnical studies to be performedin order to establish design parameters.On the east coast of the United States, thesources of earthquakes are less understood. There isno plate boundary and few locations of faults areknown. Therefore, it is difficult to make statementsabout where earthquakes are most likely to occur.Several significant historical earthquakes haveoccurred, such as in Charleston, South Carolina, in1886 and New Madrid, Missouri, in 1811 and 1812,indicating that there is potential for large earthquakes.However, most earthquakes in the easternUnited States are smaller magnitude events. Becauseof regional geologic differences, specifically, thehardness of the crustal rock, eastern and central U.S.earthquakes are felt at much greater distances fromtheir sources than those in the western United States,sometimes at distances up to a thousand miles.F.3 Earthquake EffectsMany different types of damage can occur in buildings.Damage can be divided into two categories:structural and nonstructural, both of which can behazardous to building occupants. Structural damagemeans degradation of the building’s structural supportsystems (i.e., vertical- and lateral-force-resistingsystems), such as the building frames and walls.Nonstructural damage refers to any damage that doesnot affect the integrity of the structural support systems.Examples of nonstructural damage are chimneyscollapsing, windows breaking, or ceilingsfalling. The type of damage to be expected is a complexissue that depends on the structural type and ageof the building, its configuration, construction materials,the site conditions, the proximity of the buildingto neighboring buildings, and the type of nonstructuralelements.FEMA 154 F: Earthquakes and How Buildings Resist Them 131

Figure F-3Seismicity of Alaska 1977 − 1997. The white line close to most of the earthquakes is the plateboundary, on the ocean floor, between the Pacific and North America plates.Figure F-4Seismicity of Hawaii 1977 − 1997. See Figure F-2 caption.132 F: Earthquakes and How Buildings Resist Them FEMA 154

When strong earthquake shaking occurs, a buildingis thrown mostly from side to side, and also upand down. That is, while the ground is violentlymoving from side to side, taking the building foundationwith it, the building structure tends to stay atrest, similar to a passenger standing on a bus thataccelerates quickly. Once the building starts moving,it tends to continue in the same direction, but theground moves back in the opposite direction (as ifthe bus driver first accelerated quickly, then suddenlybraked). Thus the building gets thrown back andforth by the motion of the ground, with some parts ofthe building lagging behind the foundation movement,and then moving in the opposite direction. Theforce F that an upper floor level or roof level of thebuilding should successfully resist is related to itsmass m and its acceleration a, according to Newton’slaw, F = ma. The heavier the building the more theforce is exerted. Therefore, a tall, heavy, reinforcedconcretebuilding will be subject to more force than alightweight, one-story, wood-frame house, given thesame acceleration.Damage can be due either to structural members(beams and columns) being overloaded or differentialmovements between different parts of the structure.If the structure is sufficiently strong to resistthese forces or differential movements, little damagewill result. If the structure cannot resist these forcesor differential movements, structural members willbe damaged, and collapse may occur.Building damage is related to the duration andthe severity of the ground shaking. Larger earthquakestend to shake longer and harder and thereforecause more damage to structures. Earthquakes withRichter magnitudes less than 5 rarely cause significantdamage to buildings, since acceleration levels(except when the site is on the fault) and duration ofshaking for these earthquakes are relatively small.In addition to damage caused by ground shaking,damage can be caused by buildings pounding againstone another, ground failure that causes the degradationof the building foundation, landslides, fires andtidal waves (tsunamis). Most of these “indirect”forms of damage are not addressed in this Handbook.Generally, the farther from the source of anearthquake, the less severe the motion. The rate atwhich motion decreases with distance is a function ofthe regional geology, inherent characteristics anddetails of the earthquake, and its source location. Theunderlying geology of the site can also have a significanteffect on the amplitude of the ground motionthere. Soft, loose soils tend to amplify the groundmotion and in many cases a resonance effect canmake it last longer. In such circumstances, buildingdamage can be accentuated. In the San Franciscoearthquake of 1906, damage was greater in the areaswhere buildings were constructed on loose, manmadefill and less at the tops of the rocky hills. Evenmore dramatic was the 1985 Mexico City earthquake.This earthquake occurred 250 miles from thecity, but very soft soils beneath the city amplified theground shaking enough to cause weak mid-rise buildingsto collapse (see Figure F-5). Resonance of thebuilding frequency with the amplified ground shakingfrequency played a significant role. Sites withrock close to or at the surface will be less likely toamplify motion. The type of motion felt also changeswith distance from the earthquake. Close to thesource the motion tends to be violent rapid shaking,whereas farther away the motion is normally more ofa swaying nature. Buildings will respond differentlyto the rapid shaking than to the swaying motion.Each building has its own vibrational characteristicsthat depend on building height and structuraltype. Similarly, each earthquake has its own vibrationalcharacteristics that depend on the geology ofthe site, distance from the source, and the type andsite of the earthquake source mechanism. Sometimesa natural resonant frequency of the building and aprominent frequency of the earthquake motion aresimilar and cause a sympathetic response, termedresonance. This causes an increase in the amplitudeof the building’s vibration and consequentlyincreases the potential for damage.Resonance was a major problem in the 1985Mexico City earthquake, in which the total collapseof many mid-rise buildings (Figure F-5) causedmany fatalities. Tall buildings at large distances fromthe earthquake source have a small, but finite, probabilityof being subjected to ground motions containingfrequencies that can cause resonance.Where taller, more flexible, buildings are susceptibleto distant earthquakes (swaying motion) shorterFigure F-5Mid-rise building collapse, 1985 MexicoCity earthquake.FEMA 154 F: Earthquakes and How Buildings Resist Them 133

Figure F-6Near-field effects, 1992 Landers earthquake, showing house (white arrow) close to surface faulting(black arrow); the insert shows a house interior.and stiffer buildings are more susceptible to nearbyearthquakes (rapid shaking). Figure F-6 shows theeffects on shorter, stiffer structures that are close tothe source. The inset picture shows the interior of thehouse. Accompanying the near field effects is surfacefaulting also shown in Figure F-6.The level of damage that results from a majorearthquake depends on how well a building has beendesigned and constructed. The exact type of damagecannot be predicted because no two buildingsundergo identical motion. However, there are somegeneral trends that have been observed in manyearthquakes.● Newer buildings generally sustain less damagethan older buildings designed to earlier codes.● Common problems in wood-frame constructionare the collapse of unreinforced chimneys(Figure F-7) houses sliding off their foundations(Figure F-8),collapse of cripple walls(Figure F-9), or collapse of post and pier foundations(Figure F-10). Although such damage maybe costly to repair, it is not usually life threatening.● The collapse of load bearing walls that supportan entire structure is a common form of damagein unreinforced masonry structures(Figure F-11).Figure F-7Collapsed chimney with damaged roof,1987 Whittier Narrows earthquake.● Similar types of damage have occurred in manyolder tilt-up buildings (Figure F-12).From a life-safety perspective, vulnerable buildingsneed to be clearly identified, and then strengthenedor demolished.F.4 How Buildings Resist EarthquakesAs described above, buildings experience horizontaldistortion when subjected to earthquake motion.When these distortions get large, the damage can becatastrophic. Therefore, most buildings are designed134 F: Earthquakes and How Buildings Resist Them FEMA 154

Figure F-8House that slid off foundation,1994 Northridge earthquake.Figure F-11Collapse of unreinforced masonrybearing wall, 1933 Long Beachearthquake.Figure F-9Figure F-10Collapsed cripple stud walls droppedthis house to the ground, 1992 Landersand Big Bear earthquakes.This house has settled to the ground dueto collapse of its post and pierfoundation.Figure F-12Collapse of a tilt-up bearing wall.with lateral-force-resisting systems (or seismic systems),to resist the effects of earthquake forces. Inmany cases seismic systems make a building stifferagainst horizontal forces, and thus minimize theamount of relative lateral movement and consequentlythe damage. Seismic systems are usuallydesigned to resist only forces that result from horizontalground motion, as distinct from verticalground motion.The combined action of seismic systems alongthe width and length of a building can typically resistearthquake motion from any direction. Seismic systemsdiffer from building to building because thetype of system is controlled to some extent by thebasic layout and structural elements of the building.Basically, seismic systems consist of axial-, shearandbending-resistant elements.In wood-frame, stud-wall buildings, plywoodsiding is typically used to prevent excessive lateraldeflection in the plane of the wall. Without the extrastrength provided by the plywood, walls would distortexcessively or “rack,” resulting in broken windowsand stuck doors. In older wood frame houses,FEMA 154 F: Earthquakes and How Buildings Resist Them 135

this resistance to lateral loads is provided by eitherwood or steel diagonal bracing.The earthquake-resisting systems in modern steelbuildings take many forms. In moment-resisting steelframes, the connections between the beams and thecolumns are designed to resist the rotation of the columnrelative to the beam. Thus, the beam and thecolumn work together and resist lateral movementand lateral displacement by bending. Steel framessometimes include diagonal bracing configurations,such as single diagonal braces, cross-bracing and “Kbracing.”In braced frames, horizontal loads areresisted through tension and compression forces inthe braces with resulting changed forces in the beamsand columns. Steel buildings are sometimes constructedwith moment-resistant frames in one directionand braced frames in the other.In concrete structures, shear walls are sometimesused to provide lateral resistance in the plane of thewall, in addition to moment-resisting frames. Ideally,these shear walls are continuous reinforced-concretewalls extending from the foundation to the roof ofthe building. They can be exterior walls or interiorwalls. They are interconnected with the rest of theconcrete frame, and thus resist the horizontal motionof one floor relative to another. Shear walls can alsobe constructed of reinforced masonry, using bricks orconcrete blocks.136 F: Earthquakes and How Buildings Resist Them FEMA 154

ReferencesASCE, 1998, Handbook for the SeismicEvaluation of Buildings — A Pre-standard,prepared by the American Society of CivilEngineers for the Federal EmergencyManagement Agency, FEMA 310 Report,Washington D.C.ASCE, 2000, Prestandard and Commentary forthe Seismic Rehabilitation of Buildings,prepared by the American Society of CivilEngineers for the Federal EmergencyManagement Agency, FEMA 356 Report,Washington, D.C.ATC, 1987, Evaluating the Seismic Resistance ofExisting Buildings, Applied TechnologyCouncil, ATC-14 Report, Redwood City,California.ATC, 1989, Procedures for Postearthquake SafetyEvaluation of Buildings, Applied TechnologyCouncil, ATC-20 Report, Redwood City,California.ATC, 1992, Procedures for Building SeismicRehabilitation (Interim), Applied TechnologyCouncil, ATC-26-4 Report, Redwood City,CaliforniaATC, 1995, Addendum to the ATC-20Postearthquake Building Safety ProceduresApplied Technology Council, ATC-20-2Report, Redwood City, California.ATC, 1988a, Rapid Visual Screening of Buildingsfor Potential Seismic Hazards: A Handbook,prepared by the Applied Technology Councilfor the Federal Emergency ManagementAgency, FEMA 154 Report, Washington,D.C.ATC, 1988b, Rapid Visual Screening of Buildingsfor Potential Seismic Hazards: SupportingDocumentation, prepared by the AppliedTechnology Council for the FederalEmergency Management Agency, FEMA 155Report, Washington, D.C.ATC, 1997a, NEHRP Guidelines for the SeismicRehabilitation of Buildings, prepared by theApplied Technology Council for the BuildingSeismic Safety Council, published by theFederal Emergency Management Agency,FEMA 273 Report, Washington, D.C.ATC, 1997b, NEHRP Commentary on theGuidelines for the Seismic Rehabilitation ofBuildings, prepared by the AppliedTechnology Council for the Building SeismicSafety Council, published by the FederalEmergency Management Agency, FEMA 274Report, Washington, D.C.ATC, 2002, Rapid Visual Screening of Buildingsfor Potential Seismic Hazards: SupportingDocumentation (2 nd edition), prepared by theApplied Technology Council for the FederalEmergency Management Agency, FEMA 155Report, Washington, D.C.BSSC, 1992, NEHRP Handbook for the SeismicEvaluation of Existing Buildings, prepared bythe Building Seismic Safety Council for theFederal Emergency Management Agency,FEMA 178 Report, Washington D.C.BSSC, 1997, NEHRP Recommended Provisionsfor the Seismic Regulations for New Buildingsand Other Structures, and Commentary,prepared by the Building Seismic SafetyCouncil for the Federal EmergencyManagement Agency, FEMA 302 and 303Reports, Washington, D.C.BSSC, 2000, NEHRP Recommended Provisionsfor the Seismic Regulations for New Buildingsand Other Structures, and Commentary, 2000Edition, prepared by the Building SeismicSafety Council for the Federal EmergencyManagement Agency, FEMA 368 and 369Reports, Washington, D.C.EERI, 1998, Seismic Rehabilitation of Buildings:Strategic Plan 2005, prepared by theEarthquake Engineering Research Institute forthe Federal Emergency Management Agency,FEMA 315 Report, Washington, D.C.FEMA, 1995, Typical Costs for SeismicRehabilitation of Buildings, Second Edition,FEMA 156 and 157 Reports, FederalFEMA-154 References 137

Emergency Management Agency,Washington, D.C.ICBO, 1973, 1997, Uniform Building Code,International Conference of Building Officials,Whittier, California.NBS, 1980, Development of a Probability BasedLoad Criterion for American NationalStandard A58.1, NBS Special Publication 577,National Bureau of Standards, Washington,D.C.NIBS, 1999, Earthquake Loss EstimationMethodology HAZUS, Technical Manual,Vol. 1, prepared by the National Institute ofBuilding Sciences for the Federal EmergencyManagement Agency, Washington, D.C.ROA, 1998, Planning for Seismic Rehabilitation:Societal Issues, developed for the BuildingSeismic Safety Council, by Robert OlsonAssociates, Inc., for the Federal EmergencyManagement Agency, FEMA-275 Report,Washington, D.C.SAC, 2000, Recommended Seismic DesignCriteria for New Steel Moment-FrameBuildings, prepared by the SAC Joint Venture,a partnership of the Structural EngineersAssociation of California, the AppliedTechnology Council, and CaliforniaUniversities for Research in EarthquakeEngineering, for the Federal EmergencyManagement Agency, FEMA 350 Report,Washington, D.C.VSP, 1994, Seismic Rehabilitation of FederalBuildings: A Benefit/Cost Model; Volume 1: AUsers Manual and Volume 2: SupportingDocumentation; prepared by VSP Associates,Sacramento California, for the FederalEmergency Management Agency, FEMA-255and FEMA-256 Reports, Washington, D.C.Web pagesSanborn Map Companywww.sanbornmap.comwww.lib.berkeley.edu/EART/sanborn.html138 References FEMA 154

Project ParticipantsMr. Christopher Rojahn (Principal Investigator)Applied Technology Council555 Twin Dolphin Drive, Suite 550Redwood City, California 94065Mr. Ugo MorelliFederal Emergency Management Agency500 C Street, Room 416Washington, DC 20472Project ManagementFEMA ManagementDr. Charles Scawthorn (Co-PrincipalInvestigator and Project Director)ABS Consulting1111 Broadway, 10th FloorOakland, California 94607Prof. Thalia Anagnos(San Jose State University)2631 South CourtPalo Alto, California 94306Project Advisory PanelProf. Anne S. Kiremidjian(Stanford University)1421 Berry Hills Court,Los Altos, California 94305Mr. John Baals, Seismic Safety ProgramCoordinator, U.S. Department of the InteriorBureau of ReclamationDenver Federal Center, Building 67P.O. Box 25007, D-8110Denver, Colorado 80225-0007Mr. James Cagley*Cagley & Associates6141 Executive Blvd.Rockville, Maryland 20852Mr. Melvyn GreenMelvyn Green & Associates21307 Hawthorne Blvd., Suite 250Torrance, California 90503Mr. Terry Hughes, CBOCode SpecialistHnedak Bobo Group, Inc.104 South Front StreetMemphis, Tennessee 38103* ATC Board ContactMs. Joan MacQuarrieChief Building OfficialCity of Berkeley2120 Milvia StreetBerkeley, California 94704Mr. Chris D. PolandDegenkolb Engineers225 Bush Street, Suite 1000San Francisco, California 94104Prof. Lawrence D. Reaveley(University of Utah)1702 Cannes WaySalt Lake City, Utah 84121Mr. Doug SmitsChief Building/Fire OfficialCity of Charleston75 Calhoun Street, Division 320Charleston, South Carolina 29401Mr. Ted WinsteadWinstead Engineering, Inc.2736 Gerald Ford Drive, EastCordova, Tennessee 38016FEMA-154 Project Participants 139

Mr. Kent DavidABS Consulting1111 Broadway, 10th FloorOakland, California 94607-5500Dr. Stephanie A. KingWeidlinger Associates4410 El Camino Real, Suite 110Los Altos, California 94022Technical ConsultantsMr. Richard RanousABS Consulting300 Commerce Drive, Suite 200Irvine, California 92602Dr. Nilesh ShomeABS Consulting1111 Broadway, 10th FloorOakland, California 94607-5500Mr. Vincent PrabisABS Consulting1111 Broadway, 10th FloorOakland, California 94607-5500Mr. William Holmes (Facilitator)Rutherford & Chekene427 Thirteenth StreetOakland, California 94612Workshop ConsultantsDr. Keith Porter (Recorder)California Institute of Technology1200 E. California Blvd., MC 104-44Pasadena, California 91125Dr. Gerald BradyApplied Technology Council555 Twin Dolphin Drive, Suite 550Redwood City, California 94065Mr. Peter MorkApplied Technology Council555 Twin Dolphin Drive, Suite 550Redwood City, California 94065Report Production and EditingMs. Michelle SchwartzbachApplied Technology Council555 Twin Dolphin Drive, Suite 550Redwood City, California 94065140 Project Participants FEMA-154