The AISC specification for ASD specifies the following allowable shear stresses Fv, ksi ( ksiX6.894=MPa)
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For a compact section bent about the major axis, the unbraced length Lb of the compression flange, where plastic hinges may form at failure, may not exceed Lpd, given by Eqs. given in post. For beams bent about the minor axis and square and circular beams, Lb is not restricted for plastic analysis.
The maximum fiber stress in bending for laterally supported beams and girders is Fb = 0.66Fy if they are compact, except for hybrid girders and members with yield points exceeding 65 ksi (448.1 MPa). Fb = 0.60Fy for non-compact sections. Fy is the minimum specified yield strength of the steel, ksi (MPa). Table lists values of Fb for two grades of steel.
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Plastic analysis of prismatic compression members in buildings is permitted if (Fy)½(l/r) does not exceed 800 and Fuless than equal to 65 ksi (448 MPa). For axially loaded members with b/t less than equal to (lambda)r , the maximum load P u , ksi (MPa= 6.894 X ksi), may be computed from
Pu = 0.85AgFcr
Where Ag=gross cross-sectional area of the member
F cr =0.658 lambda Fy for lambda <= 2.25
=0.877 Fy/lambda for lambda > 2.25
lambda =(Kl/r)2(Fy/286,220)
The AISC specification for LRFD presents formulas for designing members with slender elements.
The AISC specification for allowable-stress design (ASD) for buildings provides two formulas for computing allowable compressive stress Fa, ksi (MPa), for main members. The formula to use depends on the relationship of the largest effective slenderness ratio Kl/r of the cross section of any unbraced segment to a factor C c defined by the following equation and table below:
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