Numerical study on design rules for minimum degree of shear connection in propped steel-concrete composite beams

This manuscript presents a numerical study on simply supported propped composite beams with ductile shear connectors subjected to uniformly distributed load. The aim is to assess the performance of the revised rules for the minimum degree of shear connection (CEN/TC250/SC4.T3) with respect to the occurring slip. First, a nonlinear 3D finite element model was developed through the software ABAQUS 2017 and validated against analytical and full-scale beam test results. Then, 91 configurations were analysed for different degrees of shear connection eta = 0.2, 0.4, 0.6, 0.8 and 1.0. The span ranges from 6 to 25 m while the geometrical and mechanical properties varied within their typical field of applicability. According to both current and revised rules, 16 configurations with relatively deep beam and "weak" concrete slab exhibited allowable slip values smax significantly higher than 6 mm. Therefore, the authors proposed a reduction of the maximum degree of utilization to these special cases. If the proposed reduction is included in the revised rules, none of the considered cases exhibit a slip smax higher than 8 mm while few cases have smax between 6 and 8 mm. For the ease of use, a design proposal is reformulated as a conditional reduction of the plastic bending resistance of the composite section.