2001 ASD Supplements - unprotected PDF - American Wood Council

ASD STRUCTURAL LUMBER SUPPLEMENTL-9C P is 1.0for fully supported or “zero length” columns,or as given in NDS Section 3.7 otherwiseBending (Moment and Shear)The capacities for bending members can be computedby the following equations:For moment:M′ = F ′b SC r is 1.15for members used in repetitive member applicationsas defined in NDS Section 4.3.9,or 1.00 otherwiseC F is as shown in Table 4.4C L is 1.0C f is 1.0for fully laterally supported beams, or as givenin NDS Section 3.3.3 otherwisefor rectangular members loaded along a principalaxis, or as given in NDS Section 4.3.10otherwise4For shear:For a rectangular bending member of breadth, b, anddepth, d,2F ′v bdV ′ =3where:M′ and V′ are the allowable moment and shear capacities,F b ′ and F v ′ are the allowable bending and sheardesign values, S is the section modulus.The allowable bending and shear design values arecomputed by multiplying the tabulated design values by aseries of adjustment factors.The tabulated design values for F b and F v are providedin the NDS Supplement.C fu is 1.0for members loaded edgewise, or as shownin Table 4.5 for members loaded flatwiseCombined Axial & FlexuralThe design capacities for members under combinedaxial and flexural loading are based upon the equations inNDS Section 3.9. Users are directed to that section and tothe discussion of tension, compression, and bending above.BearingThe required bearing areas of members are computedbased upon the following equations:For end bearing:DESIGN ADJUSTMENT FACTORSF ′b = FbCDCMCt CiCLCFCfuCr CfF v′ = F vcC DC MC iP g′ = F c′where:and:C D is 1.0C M is 1.0C t is 1.0C i is 1.0for normal (ten years) load duration, or asshown in Table 4.1 otherwisefor 19% MC and less, or as shown in Table4.2 otherwiseunless temperatures exceed 100°F for extendedperiods of time, or as shown in Table4.3 otherwisefor members that are not incised, or as shownin Table 4.6 otherwiseand:F c′ = F cC DC tC D is 1.0C t is 1.0for normal (ten years) load duration, or asshown in Table 4.1 otherwiseunless temperatures exceed 100°F for extendedperiods of time, or as shown in Table4.3 otherwiseAMERICAN FOREST & PAPER ASSOCIATION