Experimental study, finite element simulation and theoretical analysis on failure mechanism of steel-concrete-steel (SCS) composite deep beams with UHPC

Configurations of steel faceplate (SP) and filled concrete (FC) are the main concern issue in steel- ultra-high performance concrete (UHPC) -steel (SUS) composite deep beams, which have important effects on failure modes, mechanical behaviors and interfacial slip. This paper aims to quantify the relationship between failure modes and configurations of SP. Results can be used to explore the failure mechanism and propose the theoretical models of SUS composite deep beams. 6 SUS composite deep beams were measured. Results indicate that SUS composite deep beams with different configurations of SP and FC, exhibit different failure modes, including shear without slip failure, slip failure and flexural without slip failure. Influence mechanism of SP, FC, spacing of shear studs on failure modes, mechanical behaviors and interfacial slip was explored. Failure mechanism was revealed by a modified Strut-and-Tie model. Subsequently, finite element (FE) models of SUS composite deep beams were developed to obtain the width of concrete diagonal strip, and configuration relationship between SP and FC. Based on the test results and FE results, the theoretical models of SUS composite deep beams corresponding to different failure modes were deduced and validated, considering the interfacial slip between SP and FC.