Flexural behavior of wet joints connecting step-shaped composite slab and steel beam under negative moment

This study proposed an innovative step-shaped composite (SSC) slab system that has a high assembly rate. Experimental and analytical studies were carried out to investigate the flexural behavior of wet joints connecting SSC slabs and H-shaped steel beams under negative moment. The effects of three factors were experimentally examined, including width of the horizontal laminated interface, seated length of precast slabs on steel beam, and type of wet joint materials. The crack development, load–deflection response and strain distribution were monitored during the loading. As found, the SSC slabs showed similar flexural behavior to that of the slab cast-in-situ. The seated length (10-30 mm) had a negligible effect on the flexural behavior of the SSC slabs, while the beneficial effect of using ultra-high performance concrete (UHPC) as the wet joint material was significant. Besides, using a wider horizontal laminated interface, initial cracking load and yield load could be significantly improved, though it had a marginal effect on the bearing capacity. Based on the collected bond test results, a cracking load model for SSC slabs with UHPC wet joint was proposed and validated. Finally, a refined finite element (FE) model was established and calibrated against the test results for parametric analysis.