The Dependence of Shear Lag on Loading in Composite Beams

A composite beam includes a concrete slab and a steel beam, which are connected by shear connectors. Under positive bending moment, the longitudinal compressive stresses in the concrete slab have a non-uniform distribution along the cross section because of the shear lag effect. In this work a three-dimensional linearly elastic finite element analysis has been done to study the variation of shear lag due to loading type in a composite steel concrete beam. Three types of loading cases have been investigated in this study; concentrated load, line load and uniformly distributed load. From results obtained, it was found that the longitudinal stresses distribution in the concrete slab at the midspan of a simply supported composite beam was markedly different from the uniform distribution assumed in T- beam theory and shear lag clearly affected by loading type.