Influence of shear connectors on the ultimate capacity of steel-UHPC-steel slabs subjected to concentrated loads

In steel-concrete-steel (SCS) structures, the external steel plates and the internal concrete core are composite through the shear connectors, such as tie bars and headed studs. Compared to traditional reinforced concrete (RC) structures, excellent mechanical performances and modular construction are significant advantages for SCS composite structures. To satisfy the extreme service environment for nuclear power containments and offshore platforms, ultra-high performance concrete (UHPC) is applied as the core material which forms steel-UHPC-steel composite structure. In this paper, static tests of three steel-UHPC-steel composite slabs with simple supports on four sides were conducted under concentrated loads. The failure characteristics and failure mechanism were summarized, in which a punching shear cone developed in the UHPC core and steel fibers resisted the propagation of cracks. Besides, refined numerical models of steel-UHPC-steel slab were established by Abaqus/Explicit, which considered the material damage and element deletion. The applicability of the finite element method was verified by comparing load-deflection curves and failure characteristics with the test results. On this basis, the influence of the arrangement of shear connectors on the mechanical performances of the steel-UHPC-steel slab was analyzed and discussed. Combining all the cases, flexural-slippage failure and punching shear failure were proposed according to the different composite action caused by shear connectors. Finally, the design method was enhanced, which predicted the ultimate capacity of steel-UHPC-steel composite slabs under concentrated loads. Design recommendation was provided for the arrangement of shear connectors based on controlling the failure modes.