Long-term analysis of steel-concrete composite beams: FE modelling for effective width evaluation

This paper presents a finite element model suitable for long-term analysis of steel–concrete composite beams. The structure is modelled using one-dimensional beam elements for the steel profile and two-dimensional shell elements for the concrete slab, where the two types of element are interconnected by means of special-purpose link elements. In this way, the deformability of the connection system can be taken into account, along with the shear lag phenomenon in the concrete slab. Careful consideration is taken in modelling the concrete behaviour, for which both rheological phenomena, such as creep and shrinkage, and non-linear behaviour due to cracking are fully considered for a plane stress state. Some preliminary analyses carried out on a composite girder bridge subjected to long-term loading demonstrate the applicability of the proposed method for evaluating the influence of different and complex phenomena, such as the shrinkage and cracking of concrete, on the effective width evaluation. These analyses also highlight potential shortcomings in current design codes of practice, the validation of which necessitates further experimental and numerical work.