Behavior of a new shear connector for U-shaped steel-concrete hybrid beams

Steel-concrete composite beam is an alternative to reduce the construction time and material costs compared to a conventional reinforced or prestressed concrete one when aiming to reach a large span and limiting the height of the cross-section. Composite beam consisting of a concrete beam cased in a U-shaped steel beam has been recently reported in the literature. Such composite beam is cost effective if a thin-walled steel section is used, leading to some difficulties in welding shear stud connectors. Another shear connector devices have to be used. It is worth mentioning that during concrete encasement, the upper flanges of the U-section have to be linked in order to preserve the shape of the steel cross-section. It is then proposed here to use the linking element as a shear connector. This new type of shear connection is not covered in present norms of composite structures and it requires an investigation on its behavior and on force transfer mechanisms. The experimental investigation of the behavior of these shear connectors through asymmetrical push-out tests is presented in this paper. Two different cross-sections of shear connectors were considered. A finite element model has been developed in order to identify the stress behavior of shear connectors and the surrounding concrete. A good agreement of FEA results and experimental data is obtained. Based on the FEA results, an analytical design formula for shear connectors is proposed.