###### Abstract  
With the convenient and fast requirements for construction in bridge engineering, prefabricated assembly technology is widely applied in engineering construction. Typically, prefabricated bridge decks are connected through cast-in-place wet joints. Wet joints, as the primary load-bearing parts of bridge decks, undergo complex stress and are prone to cracking and damage. Particularly in the negative bending moment region of bridges, the influence of tensile stress on wet joints is more severe, thus enhancing the mechanical performance and crack resistance of joints becomes crucial. This paper investigates the mechanical behavior of prefabricated reinforced concrete bridge deck panels with variable cross-sections under negative bending moments, focusing on the performance of Ultra High-Performance Concrete (UHPC) wet joints. Full-scale experimental tests were conducted on a 176 m steel truss composite continuous rigid bridge, employing C50 concrete panels with UHPC wet joints. Results show three distinct stages: elastic, crack initiation and propagation, and failure. The maximum failure load reached 822 kN, with a maximum displacement of 21.64 mm. Concrete strains indicate compressive stress near the wet joint and tensile stress near the loading positions. Cracks primarily develop at the wet joint interface and propagate under increasing load, ultimately leading to flexural-shear failure near the variable cross-section of the wet joint. Numerical simulations using ABAQUS/CAE (2020) corroborate experimental findings, closely matching load-displacement curves and identifying damage locations. The study demonstrates that UHPC wet joints significantly enhance crack resistance, meeting design requirements for improved mechanical performance in bridge structures subjected to negative bending moments. interfaces. Moreover, domestic researchers have found through experiments that U-shaped reinforcement greatly enhances the mechanical performance of wet joints, with varying lap lengths significantly affecting its performance [9; 10; 11; 12]. Studies by [PERSON] et al. [13] and others have investigated the mechanical properties and crack development of three types of wet joints: welded reinforcement joints, U-shaped reinforcement joints, and arc-shaped reinforcement joints proving the effective mechanical and load transmission mechanisms of wet joints. [PERSON] et al. [14] and others have examined the influence of different lap forms and lengths of U-shaped reinforcement on wet joints and conducted static tests, demonstrating that in static tensile tests, cracks tend to develop earlier at the construction joints of lateral U-shaped reinforcement, and using welded or increasing lap lengths can reduce the average stress on the reinforcement. Furthermore, research on wet joint construction has been conducted both domestically and internationally, with different construction forms significantly improving the mechanical properties of wet joints [15; 16]. [PERSON] and [PERSON] [17] and others analyzed the bending failure modes of wet joints under different construction forms, concluding that the stiffness of the upper and lower strip diamond joint beams is the highest. [PERSON] et al. [18] analyzed the mechanical properties of different forms of wet joints in bridge deck panels and experimentally demonstrated that densely welded reinforcement on steel slabs significantly improves the crack resistance of wet joints compared to unwelded wet joints on steel slabs. Most of the domestic and foreign research mentioned above mainly focuses on the mechanical properties of bridge deck panels and their wet joints under positive bending moments, with the concrete in the joint area often being high-strength concrete. However, the mechanical properties of bridge deck panels with variable cross-sections and their wet joints under negative bending moments require further investigation.