Low-temperature effects on the seismic performance of lead rubber bearings and isolated bridges: Experimental study and numerical simulation

This study investigates the effects of low temperature on the mechanical properties of lead rubber bearings (LRBs) and the seismic performance of isolated bridges through compression-shear tests and nonlinear dynamic analyses. Compression-shear tests were conducted on LRBs at six temperature levels: 30, 0, –10, –20, –30, and –40 ℃. The vertical stiffness was measured before and after cyclic shear loading to evaluate the residual vertical load-carrying capacity of the LRBs. Temperature-dependent bearing properties were identified using a bilinear model and introduced into a nonlinear finite element model for a seismically isolated bridge. Finally, 40 near-fault ground motions were selected to assess the seismic responses of the isolated bridge under different temperatures. The test results indicate that decreasing temperature causes more severe bearing damage and significantly increases the initial horizontal stiffness, shear modulus, effective stiffness, post-yield stiffness, and peak shear force of LRBs. Meanwhile, residual vertical stiffness degradation becomes more pronounced after large cyclic shear deformation at low temperatures. Nonlinear dynamic analyses indicated that low-temperature-induced bearing hardening shortened the fundamental period of the bridge and reduced the bearing shear strain and hysteretic energy dissipation capacity of LRBs. Consequently, the maximum drift ratio, curvature demand, and pier-base shear force increased as temperature decreased. These findings indicate that low temperatures significantly affect the mechanical properties of LRBs, weaken their seismic isolation effect, and lead to increased damage to bridge piers. Temperature-dependent bearing properties and residual vertical stiffness degradation should be explicitly considered in seismic design and performance evaluation of isolated bridges.