Flexural behavior of steel plate-UHPC composite wet joints for precast UHPC deck slabs

Ultra-high performance concrete (UHPC) can be used in steel-concrete composite structures to decrease selfweight, enhance mechanical properties and promote the accelerated bridge construction (ABC). However, the wet joint is always the weakest part due to fiber discontinuity at the interface, increasing the risk of cracking and water seepage. To this end, this paper proposed a novel T-shaped steel plate-UHPC composite bridge deck joint which eliminated the need for temporary brackets and formwork during casting. Further, the flexural behavior of this composite joint was experimentally investigated, concerning failure mode, stiffness, strain development, cracking characteristics and ductility, in comparison to an integral cast-in-place reinforced UHPC slab. The feasibility of natural curing was explored to reduce construction period, cost, and difficulty. The results indicated that the steel plate-UHPC composite joint performed comparably to the integral cast-in-place reinforced UHPC slab in terms of stiffness, ultimate capacity and strain development. Different steel plate configurations influenced crack distribution due to interaction effects between headed studs, UHPC and the steel plate. The main crack of steel plate-UHPC composite slab joints developed at the interface due to fiber discontinuity. The effect of curing conditions on macro-mechanical behaviors was not significant, indicating natural curing was feasible for practical engineering. When steel bars yielded, steel plate strain developed rapidly, contributing more significantly to load resistance. Finally, finite element analysis and experimental results confirmed the feasibility of this novel joint, with a crack resistance safety factor exceeding 1.8.