Mechanical behaviour of bridge expansion joint interfaces filled with novel polyurethane-modified asphalt

The use of Asphalt Plug Joints (APJs) in bridge construction has rapidly expanded due to their distinct advantages in driving comfort, shock absorption, noise reduction, and maintenance ease. However, prolonged exposure to vehicular loads and environmental factors renders this expansion joint susceptible to interface effects and stress concentration, leading to damage, particularly at the interface layers between the expansion joint pavement and the expansion joint-cross joint plate contact areas. To address issues such as stress concentration, this study proposes a polyurethane-modified asphalt concrete mixture as the joint filling material. Pull-out and inclined shear tests are used to identify a bonding agent with superior adhesive properties. Additionally, a finite element model of pull-out specimens containing bilinear cohesive elements is established to simulate the cohesive damage process of the interface layers. Through parameter design analysis, the study examines the influence of individual parameter variations on interface damage behavior, obtaining comprehensive simulated analysis data on interface crack resistance performance. Based on interface test data, a bilinear cohesive force model and a viscoelastic material model of the asphalt concrete mixture are employed to establish a scaled-down model of the improved geometry design of the new APJ. This model simulates the interface mechanical characteristics of APJs under temperature effects and vehicle loads. The results demonstrate that the bilinear cohesive force model effectively simulates the nonlinear behavior of interface bonding slip. Furthermore, the use of SZ interface bonding agents and improvements in cross joint plate form can effectively mitigate issues such as uneven settlement and low-temperature cracking.