Static and fatigue behavior of novel UHPC wet joint connections for prefabricated composite bridge deck system

This paper aims to experimentally investigate the static and fatigue flexural performance of coarse aggregate ultra-high-performance concrete (UHPC) wet joints using mechanical sleeves based on the Ningchu Expressway Project, a 3 × 35 m steel-UHPC composite bridge in China. Eight static specimens comprising casting-in-place, and longitudinal and transverse wet joint specimens, were tested under negative moments and analyzed on their load-deflection responses, strain development, and cracking behavior. The test results showed that the peak load of wet joints was below 7% lower than that of casting-in-place. The cracking strength of the wet joint specimens with S-bars and U-bars reached 55.6% and 65.7% of the casting-in-place specimens. Steam curing could increase cracking loads and ductility by more than 10% than the natural curing method, satisfying the requirements of the engineering project. The fatigue test was conducted following the load specified by the Ningchu Expressway Project. After two million cycles, the maximum crack width was 0.19 mm, and the residual strength was still maintained by 95%. These findings indicate that the proposed UHPC wet joint with mechanical sleeve connections has excellent service performance and achieves uniform and efficient load transfer of steel bars in the UHPC wet joints, as well as accelerating construction efficiency and saving labor.