Flexural behavior of wet joints in steel-UHPC composite deck slabs under hogging moment

A new type of steel-UHPC composite slabs (SUCS) with PBL shear connectors are used as bridge decks in an ultra-long-span composite cable-stayed bridge under construction in China. SUCS can be prefabricated in the factory and then transported to the construction site for assembly. The steel parts of the adjacent SUCS shall be welded together and UHPC wet joints, which are the weak parts of the bridge deck, shall be cast in-situ to finish the assembly. Full-scale tests of three SUCS with dovetail-shaped wet joint or newly-proposed construction-friendly rectangular wet joint were conducted to investigate the flexural behavior under hogging moment. Flexural failure of the interface section occurred in all specimens. The ultimate capacity and crack resistance of rectangular wet joints can be close to the dovetail-shaped wet joints with the same notch length. The phenomenon that tenons were pulled out from the rectangular notch appeared in rectangular wet joints during loading, which was especially prominent when the notch length was short, and the ultimate capacity and crack resistance would be reduced. Experimental results showed significant differences between cracking behavior of the interface and the non-interface, revealing the importance influence of wet joints on durability. The ultimate capacity was analyzed theoretically, and discussions were made on the reduction of ultimate capacity caused by wet joints. In addition, a crack width prediction model was obtained by modifying the model in GB50010-2010, which was based on the comprehensive analysis method combining bond-slip method and non-slip method. The modified model can give satisfactory prediction results of crack width for both interfacial and non-interfacial cracks.