Longitudinal shear in composite steel and concrete trusses

The distribution of longitudinal shear along an interface between steel and concrete of composite trusses is generally highly non-uniform, exhibiting peaks above truss nodes (unless after plastic redistribution). The investigation presented here examines experimentally the behaviour of two steel and concrete composite truss girders, using perforated shear connector to reach full shear connection. Experimental results have served to calibrate the non-linear 3D numerical FE model formulated using ANSYS software package. More than 30 variants of shear connections of a simple truss with Vierendeel panel at midspan have been studied, having various load–slip relationships obtained from previous research. Distinctive peaks of shear flow in the connection above truss nodes have been found within elastic behaviour–especially important for connectors loaded in fatigue–followed by plastic redistribution in plastic region. Comparison of the numerical results with proposals given in Eurocode 4 and influence of shear connection densification above truss nodes are discussed in a detail. Finally, some recommendations for practical design are presented.