Behaviour of Stiffened Composite Beams with Partial Shear Interaction Accounting for Time Effects

This paper describes an analytical model to account for the effects of creep and shrinkage on the response of composite steel-concrete beams with partial shear connection stiffened by means of longitudinal plates bolted to the bottom flange of the steel member. The particularity of this model is that the partial interaction behaviour is assumed to exist between the top slab and the joist as well as between the joist and the bolted longitudinal stiffening plate, leading to a three-layered structural representation. The weak formulation of the problem is obtained and used to derive a 13 degrees-of-freedom element whose freedoms include the axial displacements of each layer, the rotations and vertical displacements at the end nodes. A parametric study has then been carried out for the case of a simply supported beam to investigate the effects of the time-dependent behaviour of the concrete for different levels of shear connection stiffness.