Composite gravity beams subject to slab lateral movement

Abstract

The behaviour of shear studs and slabs on thirty-three composite beams with different details and differing gravity loading are investigated subject to slab lateral (in-plane) forces. The finite element analysis showed that shear studs, connecting the concrete slabs to the steel beams, yielded under a combination of gravity loading, and lateral forces. This yielding led to a decrease in the degree of composite action and an increase in beam vertical deflection. The presence of initial shear stud stress due to gravity load also caused the lateral force resistance of a shear stud group within a bay to be less than the sum of all shear stud strengths, because some shear studs fractured before others reached their capacity. A method to estimate shear stud group lateral force resistance considering this effect of gravity loading was developed. This method was found to be conservative, estimating a shear stud group lateral strength of 0.8–1.0 times that found from FEM analyses. Due to the possible reduction of composite action under lateral forces, it is recommended that the bare steel beam be designed to carry the gravity un-factored dead and live loads. Furthermore, to limit the loss of composite action, it is recommended that the shear stud group demand from lateral forces alone be less than 50% of the shear stud lateral force capacity obtained using the developed method.