ASD/LRFD Manual - American Wood Council

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ASD/LRFD Manual for Engineered Wood Construction 93 M14: SHEAR WALLS AND DIAPHRAGMS M14.1 General 94 M14.2 Design Principles 94 M14.3 Shear Walls 97 M14.4 Diaphragms 98 14 American Forest & paper association
94 M14: SHEAR WALLS AND DIAPHRAGMS M14.1 General This Chapter pertains to design of shear walls and diaphragms. These assemblies, which transfer lateral forces (wind and seismic) within the structure, are commonly designed using panel products fastened to framing members. The use of bracing systems to transfer these forces is not within the scope of this Chapter. Shear wall/diaphragm shear capacity is tabulated in the ANSI/AF&PA Special Design Provisions for Wind and Seismic (SDPWS) Supplement. M14.2 Design Principles Drag Struts/Collectors The load path for a box-type structure is from the diaphragm into the shear walls running parallel to the direction of the load (i.e., the diaphragm loads the shear walls that support it). Because the diaphragm acts like a long, deep beam, it loads each of the supporting shear walls evenly along the length of the walls. However, a wall typically contains windows and doors. The traditional model used to analyze shear walls only recognizes full height wall segments as shear wall segments. This means that at locations with windows or doors, a structural element is needed to distribute diaphragm shear over the top of the opening and into the full height segments adjacent to it. This element is called a drag strut (see Figure M14.2-1). In residential construction, the double top-plates existing in most stud walls will serve as a drag strut. It may be necessary to detail the double top plate such that no splices occur in critical zones. Or, it may be necessary to specify the use of a tension strap at butt joints to transfer these forces. The maximum force seen by drag struts is generally equal to the diaphragm design shear in the direction of the shear wall multiplied by the distance between shear wall segments. Drag struts are also used to tie together different parts of an irregularly shaped building. To simplify design, irregularly shaped buildings (such as “L” or “T” shaped) are typically divided into simple rectangles. When the structure is “reassembled” after the individual designs have been completed, drag struts are used to provide the necessary continuity between these individual segments to insure that the building will act as a whole. Figures M14.2-1, M14.2-2, and M14.2-3 and the accompanying generalized equations provide methods to calculate drag strut forces. Figure M14.2-1 Shear Wall Drag Strut V Unit shear above opening = V = v a L Unit shear below opening = V L − L Max. force in drag strut = greater of or V L L L 0 1 vaLo L1 = ( L − L ) ( L − L ) 0 V L L L 0 2 vaLo L2 = ( L − L ) ( L − L ) 0 0 0 L L 1 L O L 2 Elevation 0 = v b American Wood Council
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2005 EDITION ASD/LRFD MANUAL MANUAL
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Updates and Errata While every prec
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ii ASD/LRFD MANUAL FOR ENGINEERED W
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iv ASD/LRFD MANUAL FOR ENGINEERED W
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vi ASD/LRFD MANUAL FOR ENGINEERED W
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viii ASD/LRFD MANUAL FOR ENGINEERED
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ASD/LRFD MANUAL FOR ENGINEERED Wood
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M1: general requirements for struct
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M2: DESIGN VALUES FOR STRUCTURAL ME
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M3: Design Provisions and Equations
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M3: Design Provisions and Equations
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10 M3: Design Provisions and Equati
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12 M4: SAWN LUMBER M4.1 General Pro
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14 M4: SAWN LUMBER M4.4 Special Des
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16 M4: SAWN LUMBER Table M4.4-3 Coe
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18 M4: SAWN LUMBER Table M4.5-1a AS
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20 M4: SAWN LUMBER Table M4.5-2b AS
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22 M4: SAWN LUMBER Table M4.5-3a AS
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24 M4: SAWN LUMBER Table M4.5-4c AS
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26 M4: SAWN LUMBER Column Capacity
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28 M5: structural glued laminated t
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34 M6: ROUND TIMBER POLES AND PILES
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36 M6: ROUND TIMBER POLES AND PILES
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38 M7: PREFABRICATED WOOD I-JOISTS
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40 M7: PREFABRICATED WOOD I-JOISTS
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Page 99 and 100: 86 M11: DOWEL-TYPE FASTENERS M11.1
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Page 103 and 104: 90 M12: SPLIT RING AND SHEAR PLATE
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Page 115 and 116: 102 M16: FIRE DESIGN M16.1 General
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144 M16: FIRE DESIGN Table M16.1-10
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146 M16: FIRE DESIGN Compression Me
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156 M16: FIRE DESIGN Example 16.2-1
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158 M16: FIRE DESIGN For the fire d
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160 M16: FIRE DESIGN Figure M16.3-5
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American Forest & Paper Association
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