Innovative castable polyurethane elastomer bearing system for highway bridges: Mechanical properties and performance evaluation

Abstract

This study developed a castable polyurethane elastomer (CPUE) bearing system for bridges, consisting of fixed bearings and sliding bearings. The fixed bearing is composed of polyurethane elastomer (PUE) combined with nine layers of steel plates, while the sliding bearing is formed by casting PUE with five layers of steel plates, with a 3 mm layer of polytetrafluoroethylene (PTFE) adhered to the top surface. PUE was synthesized using organosilicon diol, TDI-100, PCL-210N, and MOCA, and its mechanism was analyzed through ATR-FTIR, XRD, SEM, DSC, and DMA techniques. The PUE exhibited a glass transition temperature (Tg) of −24.8°C, ensuring flexibility under low-temperature conditions. Mechanical performance tests revealed that the vertical stiffness of the fixed and sliding bearings under 20 MPa stress was 2636.56 kN/mm and 2167.73 kN/mm, respectively, demonstrating excellent load-bearing capacity. Under cyclic shear strain of 100 % and 0.05 Hz frequency, the fixed bearing maintained a stable equivalent damping ratio of 13.6 ± 0.5 %, while the sliding bearing achieved a friction coefficient of 0.045 with PTFE. Horizontal shear tests under varying frequencies (0.005–0.1 Hz), temperatures (-10°C to 80°C), pressures (10–30 MPa), shear strains (50–250 %), and repeated loading (50 cycles at 100 % strain) showed no failure of the CPUE bearings, with residual deformation less than 5 % of initial displacement, indicating good hysteresis performance and resistance to deformation. This study provides a reference for the application of CPUE bearing systems in long-span bridges with high load-bearing requirements.