Abstract：Segmented-casting UHPC joint of steel-UHPC composite bridge deck may lead to degradation of its local tensile performance, which may further result in severe durability and safety problem of bridge deck. Direct tensile test and theoretical analysis were conducted on UHPC rectangular joint of steel-UHPC composite bridge deck. Based on axial tension tests, the impact of reinforcement ratio on axial tension behavior of rectangular joint was investigated, the crack resistance mechanism of rectangular joint was explained, and the interfacial bond strength of UHPC was discussed. Test results show that the crack of rectangular joint initiated at the corner of rectangular joint. The crack of UHPC layer around joint didn’t propagate prominently, and fracture surface of joint is relatively flat compared with that of continuous UHPC layer. The crack resistance of transverse edges and slip resistance of longitudinal edges contribute to the crack resistance of rectangular joint. Bond strength of UHPC rectangular joint under axial tension is 3.6～4.7MPa. According to test results, for UHPC rectangular joint under axial tension, the recommended design axial tension of joint was lower than 3.5MPa and 6.0MPa for forbidding crack and allowing the maximum crack width of 0.05mm respectively. Besides, equivalent residual tensile strength of UHPC in the softening stage of axial tension constitutive model was proposed basedon energy equivalence principle and simplification of softening stage for UHPC axial tension constitutive model, and the calculation formula for main crack spacing of R-UHPC member under axial tension was derived. Compared with the experimental results, the derived formula for calculating crack spacing has a high accuracy, and could provide theoretical reference for practical engineering application.
