47.5 MB - The Whole Building Design Guide

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Loads and Attachment Methods 9Information on loads on rooftop equipment was first introducedin the 2002 edition of ASCE 7. For guidance on load calculations,see “Calculating Wind Loads and Anchorage Requirements forRooftop Equipment” (ASHRAE, 2006). A minimum safety factorof 3 is recommended for critical facilities. Loads and resistanceshould also be calculated for heavy pieces of equipment since thedead load of the equipment is often inadequate to resist the designwind load. The 30’ x 10’ x 8’ 18,000-pound HVAC unit shownin Figure 3-69 was attached to its curb with 16 straps (one screwper strap). Although the wind speeds were estimatedto be only 85 to 95 miles per hour(peak gust), the HVAC unit blew off the medicaloffice building.To anchor fans, small HVAC units, and reliefair hoods, the minimum attachmentschedule provided in Table 3-2 is recommended.The attachment of the curb to theroof deck also needs to be designed and constructedto resist the design loads.Mechanical penetrations through theelevator penthouse roof and walls mustpossess adequate wind and waterresistance to ensure continuity of elevatorservice (see Section 3.3.3.3). In additionto paying special attention to equipmentattachment, air intakes and exhaustsshould be designed and constructed toprevent wind-driven water from enteringthe penthouse.Figure 3-69:Although this 18,000-pound HVAC unit wasattached to its curb with16 straps, it blew offduring Hurricane Ivan.(Florida, 2004)9. Discussion is based on: Attachment of Rooftop Equipment in High-wind Regions—Hurricane Katrina Recovery Advisory (May 2006,revised July 2006)MAKING CRITICAL FACILITIES SAFE FROM High Wind3-83
Table 3-2: Number of #12 Screws for Base Case Attachment of Rooftop EquipmentCase No Curb Size and Equipment Type Equipment AttachmentFastener Factorfor Each Side ofCurb or Flange12345612” x 12” Curb with GooseneckRelief Air Hood12” x 12” Gooseneck Relief AirHood with Flange12” x 12” Gooseneck Relief AirHood with Flange24” x 24” Curb with GooseneckRelief Air Hood24” x 24” Gooseneck Relief AirHood with Flange24” x 24” Gooseneck Relief AirHood with FlangeHood Screwed to Curb 1.6Flange Screwed to 22 GaugeSteel Roof DeckFlange Screwed to 15/32” OSBRoof Deck2.82.9Hood Screwed to Curb 4.6Flange Screwed to 22 GaugeSteel Roof DeckFlange Screwed to 15/32” OSBRoof Deck7 24” x 24” Curb with Exhaust Fan Fan Screwed to Curb 2.58 36” x 36” Curb with Exhaust Fan Fan Screwed to Curb 3.39105’-9” x 3’- 8” Curb with 2’- 8”high HVAC Unit5’-9 ”x 3’- 8” Curb with 2’- 8”high Relief Air Hood8.18.2HVAC Unit Screwed to Curb 4.5*Hood Screwed to Curb 35.6*Notes to Table 3-2:1. The loads are based on ASCE 7-05. The resistance includes equipment weight.2. The Base Case for the tabulated numbers of #12 screws (or ¼ pan-head screws for flange-attachment) is a 90-mph basic windspeed, 1.15 importance factor, 30’ building height, Exposure C, using a safety factor of 3.V 2 D( )3. For other basic wind speeds, multiply the tabulated number of #12 screws by to determine the required number90 2of #12 screws (or ¼ pan-head screws) required for the desired basic wind speed, V D(mph).4. For other roof heights up to 200’, multiply the tabulated number of #12 screws by (1.00 + 0.003 [h - 30]) to determine therequired number of #12 screws or ¼ pan-head screws for buildings between 30’ and 200’.Example A: 24” x 24” exhaust fan screwed to curb (table row 7), Base Case conditions (see Note 1): 2.5 screws per side;therefore, round up and specify 3 screws per side.Example B: 24” x 24” exhaust fan screwed to curb (table row 7), Base Case conditions, except 120 mph: 120 2 x 1 ÷ 90 2 =1.78 x 2.5 screws per side = 4.44 screws per side; therefore, round down and specify 4 screws per side.Example C: 24” x 24” exhaust fan screwed to curb (table row 7), Base Case conditions, except 150’ roof height: 1.00 +0.003 (150’ - 30’) = 1.00 + 0.36 = 1.36 x 2.5 screws per side = 3.4 screws per side; therefore, round down and specify 3screws per side.* This factor only applies to the long sides. At the short sides, use the fastener spacing used at the long sides.3-84 MAKING CRITICAL FACILITIES SAFE FROM High Wind
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Risk Management SeriesDesign Guidef
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Any opinions, findings, conclusions
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ational during and after a major di
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TARGET AUDIENCEThis manual describe
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Appendix A contains a list of acron
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Forster, FEMA; David Godschalk, Uni
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Chapter 2- Making Critical faciliti
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2.4.6 Utility Installations .......
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4.4.8 Utility Plumbing Systems.....
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avoid them when feasible. In cases
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It then crossed Florida into the Gu
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Figure 1-2: Mississippi coast SLOSH
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isks for the facility at the propos
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m Appoint a building program manage
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-Figure 1-3: Process flow chart for
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hazards, usually refers to a buildi
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occurrence during a specified time
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ut is moderate overall. Some hazard
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words, the acceptable performance o
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prior to the onset of this level of
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1.4 REFERENCESAmerican Society of C
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MAKING CRITICAL FACILITIES SAFE FRO
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m Land subsidence, which increases
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valley or the presence of obstructi
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2.1.1.1 Probability of Occurrence o
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year, a very low probability flood
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m FIRMs and Flood Insurance Studies
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Figure 2-3: Riverine flood hazard z
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have been prepared by the U.S. Army
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ABFEs represent the best estimate o
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The following characteristics that
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Figure 2-7 shows the general relati
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2.1.2.5 Hydrodynamic LoadsWater flo
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stillwater depth) and that waves pr
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Debris velocity: The velocity of th
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The most convincing evidence of the
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2.1.3.2 Summary of the NFIP Minimum
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complished through a State permit,
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Developed through a consensus proce
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2.2 CRITICAL FACILITIES EXPOSED TOF
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listed includes health hazards, los
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overview on performance-based desig
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Figure 2-12:Katrina’s storm surge
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Buoyancy and uplift: If below-grade
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acceptable, depending on the type o
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Metal components: Metal structural
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Emergency power generators: Generat
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Office records and police files: Wh
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2.3 REQUIREMENTS AND BESTPRACTICES
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terior drainage (on the land side);
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Slab-on-grade foundation on structu
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and debris and ice impact loads. Fl
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are capable of withstanding direct
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pressure, hydrodynamic loads, wave
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may significantly reduce the certai
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2.3.2.1 Elevation ConsiderationsThe
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Figure 2-30:Flood hazard zones inco
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path when designing and specifying
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ular attention to underfloor utilit
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2.3.5.4 Storage Tank InstallationsA
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2.4.2 SITE MODIFICATIONSA plan to m
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Mobilized floodwall: This category
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methods used to move other types of
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Even if a facility is unlikely to s
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Wastewater system components become
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Emergency barriers are measures of
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2.5 CHECKLIST FOR BUILDINGVULNERABI
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Table 2-3: Checklist for Building V
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FEMA, Protecting Building Utilities
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MAKING CRITICAL FACILITIES SAFE FRO
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flow is typically 6,000 to 12,000 f
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Tornado: This is a violently rotati
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Figure 3-3: Design wind speeds for
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Exposure: The characteristics of th
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Internal pressure (building pressur
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Figure 3-7:Schematic of internalpre
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Figure 3-8: Relative roof uplift pr
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larities will normally be based on
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spread in both of those storms. Pri
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and subsequent progressive failure;
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3.2 CRITICAL FACILITIES EXPOSED TOH
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Wall coverings, soffits, and large
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oof panels were applied over metal
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3.2.2 Evaluating Critical Facilitie
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Step 2: Perform a field investigati
Page 180 and 181: 3.3.1.1 SiteWhen selecting land for
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Page 184 and 185: As part of the detailed design effo
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Page 188 and 189: a window submittal should show that
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Page 192 and 193: Figure 3-23:View looking down at th
Page 194 and 195: m For buildings that have mechanica
Page 196 and 197: sionals should also specify the att
Page 198 and 199: Figure 3-31:Door sill pan flashing
Page 200 and 201: Adjustable jamb/head weatherstrippi
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Page 204 and 205: Soffits: Depending on the wind dire
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Page 208 and 209: Figure 3-47:These four ties werenev
Page 210 and 211: m Install ties as the brick is laid
Page 212 and 213: At the hospital shown in Figure 3-5
Page 214 and 215: etween the hospital and the medical
Page 216 and 217: metal panels were attached with con
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Page 220 and 221: If the roof system is fully adhered
Page 222 and 223: Figure 3-60:View of the underside o
Page 224 and 225: ities. For FMG-insured facilities,
Page 226 and 227: Figure 3-65:The original modifiedbi
Page 228 and 229: Figure 3-66:If mechanically attache
Page 232 and 233: Fan cowling attachment: Fans are fr
Page 234 and 235: Condenser attachment: In lieu of pl
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Page 238 and 239: Figure 3-78:Collapsed hospital ligh
Page 240 and 241: Figure 3-80:The antenna tower atthi
Page 242 and 243: Table 3-3: Risk Reduction Design Me
Page 244 and 245: Table 3-3: Risk Reduction Design Me
Page 246 and 247: Chapter 4 for information on the pe
Page 248 and 249: Figure 3-83:Open walkways donot pro
Page 250 and 251: ASTM E 1996 specifies five missile
Page 252 and 253: ASCE 7 refers to ASTM E 1996 for mi
Page 254 and 255: For interior non-load-bearing mason
Page 256 and 257: m For structural metal roofs, it is
Page 258 and 259: Mechanically attached and air-press
Page 260 and 261: Figure 3-92:To avoid walkway padblo
Page 262 and 263: 3.4.4.2 Mechanical PenthousesBy pla
Page 264 and 265: To enhance the wind performance of
Page 266 and 267: Mechanically attached single-ply me
Page 268 and 269: to power generation stations and by
Page 270 and 271: occupants can have bottled water pr
Page 272 and 273: Table 3-4: Recommendations for Desi
Page 274 and 275: Strong and violent tornadoes can ge
Page 276 and 277: For critical facilities located in
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funds are not available for strengt
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Figure 3-106:The school’s built-u
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3.6.2 Building EnvelopeThe followin
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Shutters are typically a more econo
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semblies with laminated glass assem
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Figure 3-116:The edge nailer on top
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Figure 3-118:The antenna at thishos
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3.7 Checklist for BuildingVulnerabi
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3.8 References and Sources ofAdditi
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American Society for Testing and Ma
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FEMA, Attachment of Brick Veneer in
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accompanied with suggestions on pos
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Hurricane Katrina emphasized the fa
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The water supply was interrupted an
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Hancock Medical Center in Bay St. L
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Figure 4-4:Penthouse at the WestJef
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Figure 4-6:Repair of EIFS wallcover
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The primary cause of window breakag
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West Jefferson Medical Center lost
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4.2.8 Mechanical and ElectricalSyst
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covering the fill cap and all vent
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emergency communications frequently
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mary and West Jefferson Medical Cen
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4.3 EDUCATIONAL FACILITIES4.3.1 Bac
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4.3.2 Effects of FloodingThe most d
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Figure 4-17:Broken windows atD’Ib
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St. Stanislaus High School in Bay S
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4.3.6 Structural SystemsMost of the
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The St. Stanislaus High School camp
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Figure 4-27:Metal roof covering pee
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ment, especially HVAC systems, was
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Figure 4-30:Interior damage at Char
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m Doors should be designed to meet
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different, most of them require and
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4.4.3 Effects of High WindsThe high
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Figure 4-33:Jackson County EOCFigur
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them experienced significant proble
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Figure 4-37:Back Bay Fire Company#3
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Figure 4-39:Gulfport Fire Station #
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Third District Fire Station in New
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Figure 4-44:Roof damage at HancockC
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underground tank for toilets and wa
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Figure 4-47:Generator mounted atgra
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Figure 4-49:Broken communicationsma
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erate without adequate emergency po
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FISFMAFMGFMRHMGPIBCICCICULPSMEPSMOB
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Building, enclosed. A building that
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Floodway. The channel and that port
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OOpenings. Apertures or holes in th
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FEMA Mitigation ProgramscFederal fu
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Table 1: Side-by-Side of FEMA Progr
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todial care facilities (including t
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aged windows with impact-resistant
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tions, and wastewater treatment pla
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