2001 ASD/LRFD Wind/Seismic Supplement - American Wood Council

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ASD/LRFD SUPPLEMENT – SPECIAL DESIGN PROVISIONS FOR WIND AND SEISMIC214.3.4 Shear Wall Aspect RatiosSize and shape of shear walls shall be limited to theaspect ratios in Table 4.3.4.Table 4.3.4Maximum Shear WallAspect RatiosShear WallMaximumSheathing Typeh/b s RatioWood structural panels, all edges nailed 3½:1 1Particleboard, all edges nailed 2:1Diagonal Sheathing, conventional 2:1Gypsum wallboard 2 2:1Portland Cement Plaster 2 2:1Fiberboard 1½:11For design to resist seismic forces, the shear wall aspect ratio shall notexceed 2:1 unless the nominal unit shear capacity is multiplied by 2b s /h. Inno case shall the aspect ratio exceed 3½:1.2Walls having aspect ratios exceeding 1½:1 shall be blocked.4.3.4.1 Aspect Ratio of Perforated Shear Wall Segments:The aspect ratio limitations of 4.3.4 shall apply toperforated shear wall segments within a perforated shearwall. For design to resist seismic forces, the nominal shearcapacity of the perforated shear wall shall be multipliedby 2b s /h when the aspect ratio of any perforated shearwall segment included in the sum of shear wall segmentlengths, ∑L i , is greater than 2:1, but does not exceed 3½:1.Portions of walls with aspect ratios in excess of 3½:1 shallnot be counted in the sum of shear wall segments.4.3.5 Shear Walls With OpeningsThe provisions of this section shall apply to the designof shear walls with openings. Where framing andconnections around the openings are designed for forcetransfer around the openings the provisions of 4.3.5.1 shallapply. Where framing and connections around the openingare not designed for force transfer around the openingsthe provisions of 4.3.5.2 shall apply.4.3.5.1 Force Transfer Around Openings: Whereshear walls with openings are designed for force transferaround the openings, the aspect ratio limitations of 4.3.4shall apply to the overall shear wall including openingsand to each wall pier at the sides of an opening. The heightof a wall pier shall be defined as the clear height of thepier at the side of an opening. The length of a wall piershall be defined as the sheathed length of the pier. Designfor force transfer shall be based on a rational analysis.The length of a wall pier shall not be less than 2 feet.4.3.5.2 Perforated Shear Walls: Where wood structuralpanel shear walls with openings are not designed forforce transfer around the opening, they shall be designedas perforated shear walls. The following limitations shallapply:a. A perforated shear wall segment shall be locatedat each end of a perforated shear wall.Openings shall be permitted to occur beyondthe ends of the perforated shear wall, howeverthe length of such openings shall not beincluded in the length of the perforated shearwall.b. The nominal unit shear capacity shall not exceed2,000 plf.c. Where out of plane offsets occur, portions ofthe wall on each side of the offset shall beconsidered as separate perforated shear walls.d. Collectors for shear transfer shall be providedthrough the full length of the perforated shearwall.e. A perforated shear wall shall have uniformtop of wall and bottom of wall elevations.Perforated shear walls not having uniformelevations shall be designed by other methods.f. Perforated shear wall height, h, shall not exceed20 feet.4.3.6 Construction Requirements4.3.6.1 Framing Requirements: All framing used forshear wall construction shall be 2x nominal or larger members.Shear wall boundary elements, such as end posts,shall be provided to transmit the design tension and compressionforces. Shear wall sheathing shall not be used tosplice boundary elements. End posts (studs or columns)shall be framed to provide full end bearing.a. Tension and Compression Chords: Tensionforce, T, and a compression force, C, resultingfrom shear wall overturning forces at eachstory level shall be calculated in accordancewith the following:where:T = C = ν h(4.3-4)C = Compression chord force, lbs.h = Shear wall height, ft.T = Tension chord force, lbs.ν = Induced unit shear, lbs./ft.4LATERAL FORCE-RESISTING SYSTEMSAMERICAN FOREST & PAPER ASSOCIATION
22 LATERAL FORCE-RESISTING SYSTEMSEach end of each perforated shear wall shall be designedfor a tension force, T, and a compression force, C.Each end of each perforated shear wall segment shall bedesigned for a compression force, C, in each segment.For perforated shear walls, the values for T and C resultingfrom shear wall overturning forces at each story levelshall be calculated in accordance with the following:where:VhT = C =C LC o∑L io∑i(4.3-5)= Shear capacity adjustment factor from Table4.3.3.4V = Induced shear force in perforated shear wall, lbs.= Sum of perforated shear wall segment lengths,ft.4.3.6.2 Sheathing: Shear walls shall be sheathed withapproved materials. Sheathing nails or other approvedsheathing connectors shall be driven flush with the surfaceof the sheathing. Details on sheathing types andthicknesses for commonly used shear wall assemblies areprovided in 4.3.7 and Tables 4.3A, B, and C.4.3.6.3 Fasteners: Sheathing shall be attached to framingusing approved fasteners. Details on type, size, andspacing of mechanical fasteners in commonly used shearwall assemblies are provided in 4.3.7 and Tables 4.3A, B,and C.a. Adhesives: Adhesive attachment of shear wallsheathing is not permitted as a substitute formechanical fasteners. Approved adhesive attachmentsystems shall be permitted in SeismicDesign Categories A and B where R = 1.5 andΩ 0 = 2.5 unless other values are approved. InSeismic Design Categories C-F, adhesive attachmentof shear wall sheathing is notpermitted.4.3.6.4 Shear Wall Anchorage and Load Path: Designof shear wall anchorage and load path shall conformto the requirements of this section, or shall be calculatedusing principles of mechanics.a. Anchorage for In-plane Shear: Connectionsshall be provided to transfer the induced unitshear force, ν, into and out of each shear wall.(1) In-plane Shear Anchorage for PerforatedShear Walls: The maximum induced unitshear force, ν max , transmitted into the topof a perforated shear wall, out of the baseof the perforated shear wall at full heightsheathing, and into collectors (drag struts)Vν max=Co∑Liconnecting shear wall segments, shall becalculated in accordance with the following:b. Uplift Anchorage at Shear Wall Ends: Wherethe dead load stabilizing moment is not sufficientto prevent uplift due to overturningmoments on the wall (from 4.3.6.1a), an anchoringdevice shall be provided at the endof each shear wall.(1) Uplift Anchorage for Perforated ShearWalls: In addition to the requirements of4.3.6.4.b, perforated shear wall bottomplates at full height sheathing shall be anchoredfor a uniform uplift force, t, equalto the unit shear force, ν, determined inSection 4.3.6.4.a.(1) or calculated by rationalanalysis.c. Anchor Bolts: Foundation anchor bolts shallhave a steel plate washer under each nut notless than 2½" x 2½" x ¼". The plate washershall extend to within ½" of the edge of thebottom plate on the sheathed side.d. Load Path: A load path to the foundation shallbe provided for uplift, shear, and compressionforces. Elements resisting shear wallforces contributed by multiple stories shallbe designed for the sum of forces contributedby each story.4.3.7 Shear Wall Systems(4.3-6)4.3.7.1 Wood Structural Panel Shear Walls: Shearwalls sheathed with wood structural panel sheathing shallbe permitted to be used to resist seismic and wind forces.The size and spacing of fasteners at shear wall boundaries,panel edges, and intermediate supports shall be asprovided in Table 4.3A. The shear wall shall be constructedas follows:a. Panels installed either horizontally or verticallywith panel joints occurring overcommon studs or blocking. Panels not lessthan 4 ft. x 8 ft. except that a single panelwith a minimum dimension of 1 foot is permittedif it is fully blocked and nailed.b. Nails spaced not less than 3/8 inch from edgesand ends of panels, studs, blocking, and topand bottom plates. Maximum nail spacingAMERICAN WOOD COUNCIL
Page 1 and 2: 2001 EDITIONSUPPLEMENTSpecial Desig
Page 3 and 4: ASD/LRFD SUPPLEMENT - SPECIAL DESIG
Page 9 and 10: 6 GENERAL DESIGN REQUIREMENTSG aG a
Page 11 and 12: 8 MEMBERS AND CONNECTIONS3.1 Framin
Page 13 and 14: 10 MEMBERS AND CONNECTIONS3.2.3 Roo
Page 20 and 21: Table 4.2B Nominal Unit Shear Value

2001 ASD/LRFD Wind/Seismic Supplement - American Wood Council

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