Study on the Basic Performance Deterioration Law and the Application of Lead Rubber Bearings under the Alternation of Aging and Seawater Erosion

Lead rubber isolation bearings are well-recognized as a common and effective means to mitigate the seismic responses of bridges. However, rubber isolation bearings used in offshore bridges are extremely vulnerable to the action of the alternation of aging and seawater erosion caused by weather conditions, wind, waves, and other factors. Meanwhile, the deterioration law and application of lead rubber bearings subject to the effect of aging and seawater erosion cycles are not clear. Thus, aging and seawater erosion cycles testing on both lead rubber isolation bearings (LRB) and rubber materials were carried out. The parameters for the Mooney–Rivlin model of the rubber material used in LRBs were determined and the time-varying law of basic performance of LRBs was obtained based on test results of LRBs and their rubber material. Then, the determined rubber material parameters were applied into the finite-element model of LRBs to verify the basic performance degradation law of the LRBs. Finally, the obtained basic performance degradation law of LRBs was substituted into the finite model of offshore bridges to investigate the impact of the property degradation of LRBs on their seismic performance. The time-varying law of seismic performance of offshore bridge structures was also studied based on finite element analysis. The results show that both the horizontal and vertical stiffness of LRBs increase with the alternating of aging and seawater erosion time, and the horizontal and vertical stiffness increase by 16.1% and 24.3%, respectively, during the 120-year service period. Additionally, the Mooney–Rivlin model parameters of the LRB rubber material are also significantly affected by the alternating of aging and seawater erosion. Additionally, the results also indicate the deterioration of LRBs has a great influence on the anti-seismic performance of offshore bridge structures. After 120 years of service of offshore bridge isolation bearings under the alternating of aging and seawater erosion, the maximum displacement of the pier top of the offshore bridges, the maximum bending moment at the pier bottom, and the maximum displacement of the rubber bearing increased by 14.2%, 6.6%, and 9.1%, respectively. The findings of this paper play an important role in the seismic behavior study and the life-cycle performance analysis of offshore traffic projects such as sea-crossing bridges in marine environments. At the same time, they also lay a theoretical foundation for the performance analysis of rubber isolation bearings and offshore bridge structures under the alternation of aging and seawater erosion cycles.

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