AISC LRFD 1.pdf

Comm. J4.] DESIGN RUPTURE STRENGTH 247the bolt holes. The block shear failure mode is not limited to the coped ends ofbeams. Other examples are shown in Figure C-J4.1 and C-J4.2.The block shear failure mode should also be checked around the periphery ofwelded connections. Welded connection block shear is determined using = 0.75 inconjunction with the area of both the fracture and yielding planes (Yura, 1988).The LRFD Specification has adopted a conservative model to predict block shearstrength. Test results suggest that it is reasonable to add the yield strength on oneplane to the rupture strength of the perpendicular plane (Ricles and Yura, 1983, andHardash and Bjorhovde, 1985). Therefore, two possible block shear strengths canbe calculated; rupture strength F u on the net tensile section along with shear yielding0.6F y on the gross section on the shear plane(s), or rupture 0.6F u on the net sheararea(s) combined with yielding F y on the gross tensile area. This is the basis ofEquations J4-3a and J4-3b.These equations are consistent with the philosophy in Chapter D for tension members,where gross area is used for the limit state of yielding and net area is used forrupture. The controlling equation is the one that produces the larger rupture force.Fig. C-J4.1. Failure for block shear rupture limit state.Fig. C-J4.2. Block shear rupture in tension.LRFD Specification for Structural Steel Buildings, December 27, 1999AMERICAN INSTITUTE OF STEEL CONSTRUCTION