Mechanical properties of steel-UHPC-steel slabs under concentrated loads considering composite action

Abstract

Steel-concrete-steel (SCS) composite structure is widely used as the protective structure in the containment of nuclear power plants, offshore platforms, subsea tunnels, and so on. This study investigates the mechanical properties of SCS composite slabs with ultra-high performance concrete (UHPC) as the core material under concentrated loads. Five S-UHPC-S composite slabs were tested with different parameters of the spacing of headed studs and the thickness of the concrete core. Besides, one S-C-S composite slab with the normal concrete as the core material was tested for comparison. Two failure modes, i.e. punching shear failure and interfacial debonding failure, were defined considering different composite action between the concrete core and bottom steel plate. A punching shear cone was formed in punching shear failure, while interfacial debonding failure had an obvious interfacial slippage between the concrete core and bottom steel plate. The failure mechanism of these two failure modes was analyzed. Moreover, a design method to predict bearing capacities was developed, which could take the effect of the concrete core, steel fibers in UHPC, steel plates, and tie bars into consideration. In particular, a reduction coefficient was introduced to reflect the effect of composite action between the concrete core and bottom steel plate. The design method was suitable with six specimens in this study and other specimens in literature, which could provide theoretical guidance for the application of SCS composite structure in practical engineering.