Experimental research on the time-varying law of performance for natural rubber laminated bearings subjected to seawater dry-wet cycles

Natural rubber laminated bearings (NRBs) in sea-crossing or offshore bridges are extremely vulnerable to seawater dry-wet cycles due to weather conditions, wind, waves, and other factors in coastal areas. Seawater dry-wet cycles test was conducted on 20 NRBs and 63 rubber sheets for 60 days to investigate the influence of seawater dry-wet cycles on basic NRB performance. The change laws that govern the NRBs’ horizontal and vertical stiffness were obtained via seawater dry-wet cycles test. In addition, the proposed constitutive parameters of the rubber material were used to establish a finite-element model of the NRBs to simulate and analyze the bearings’ performance and time-varying law. The test results were then compared with the fitted and simulated results. Finally, the performance deterioration law of the NRBs was predicted over a 120-year lifespan based on the extrapolation of the 60-day test results, and the finite element analysis of the performance for NRB within 120-year service life was done to verify the reliable of the prediction result. The 60 days test results show that the NRBs’ horizontal and vertical stiffness increased by 23% and 7%, respectively, after test for 60 days, and horizontal and vertical stiffness increased linearly as the seawater dry-wet cycles test time increased. The findings presented in this paper lay a foundation for further research on the performance of NRBs and will play an important role in the study of the seismic resistance and life-cycle performance of sea-crossing bridges and other structures subjected to seawater dry-wet cycles.