AISC LRFD 1.pdf

Comm. B5.] LOCAL BUCKLING 179(c) All members having only two fasteners per line in the direction of stress, U =0.75.When a tension load is transmitted by fillet welds to some but not all elements of across section, the weld strength will control.B5. LOCAL BUCKLINGFor the purposes of this Specification, steel sections are divided into compactsections, noncompact sections, and sections with slender compression elements.Compact sections are capable of developing a fully plastic stress distribution andthey possess a rotational capacity of approximately 3 before the onset of local buckling(Yura, Galambos, and Ravindra, 1978). Noncompact sections can develop theyield stress in compression elements before local buckling occurs, but will notresist inelastic local buckling at the strain levels required for a fully plastic stressdistribution. Slender compression elements buckle elastically before the yieldstress is achieved.The dividing line between compact and noncompact sections is the limitingwidth-thickness ratio p . For a section to be compact, all of its compression elementsmust have width-thickness ratios equal to or smaller than the limiting p .Fig. C-B3.2. Staggered holes.Fig. C-B3.3. Longitudinal and transverse welds.LRFD Specification for Structural Steel Buildings, December 27, 1999AMERICAN INSTITUTE OF STEEL CONSTRUCTION