Nonlinear finite-element analysis of composite steel girder bridges

This paper investigates the behavior of composite steel girder bridges by means of sophisticated three-dimensional nonlinear finite-element (FE) analyses. The bridge model is such that the deck is represented by shear flexible shell elements and the structural steel girder is idealized by Timoshenko beam elements. The full composite action between slab and girder is guaranteed by multipoint constraints. Both the bridge deck and steel girder are divided into a number of layers to account for the cracking and yielding through their depth. This paper also presents a reinforced concrete material model, which utilizes a strain decomposition approach. The strain decomposition technique enables the explicit inclusion of physical behavior across the cracked concrete surface, such as aggregate interlock and dowel action, rather than intuitively defining the shear retention factor. The proposed material model is integrated into the commercial FE software ABAQUS shell elements through a user-supplied material subroutine. The FE results have been compared to experimental results reported by other researchers. The proposed bridge FE model is capable of predicting the initial cracking load level, the ultimate load capacity, and the crack pattern with good accuracy.