基于高阻尼橡胶支座及墩柱劣化的近海隔震桥梁地震响应分析

Seismic response analysis of offshore isolated bridge based on performance degradation of high damping rubber bearing and pier

为研究高阻尼橡胶支座及墩柱材料性能退化对近海隔震桥梁在服役期内抗震性能的影响规律,给近海隔震桥梁的全寿命性能评估提供理论依据,首先,对高阻尼橡胶支座进行海水干湿循环作用下的性能劣化试验,得到相应的力学性能劣化时变模型,给出全寿命周期内高阻尼橡胶支座力学性能时变参数,并基于钢筋力学性能和混凝土材料退化模型,计算全寿命周期内钢筋和混凝土的时变参数,分析纵筋单独劣化、箍筋单独劣化及二者共同劣化3种工况条件下,桥墩截面的抗弯承载力及延性在全寿命周期内的时变规律。随后,采用SAP2000软件建立近海隔震桥梁非线性有限元模型,设计支座单独劣化、墩柱单独劣化、支座和墩柱共同劣化3种工况,分析对比不同工况下桥梁的地震响应时变规律。结果表明:箍筋劣化导致桥墩截面的延性显著降低,但对截面抗弯承载能力影响不大,纵筋劣化则相反,二者共同劣化使得桥墩截面的抗弯能力和延性均大幅下降;墩柱单独劣化和支座单独劣化对桥墩反应和支座滞回曲线均有影响,但相比于支座性能和墩柱材料单独劣化,二者共同作用时影响最大;随着服役时间的增加,墩顶位移和墩底弯矩-转角滞回面积逐渐增大,而墩底弯矩和支座滞回面积均变小;隔震桥梁的抗震性能受极罕遇地震的影响较大,极罕遇地震作用下,桥墩及支座的地震响应均显著增大。

In order to study the influence of performance degradation of high-damping rubber bearings and material of pier on seismic performance of offshore isolated bridges during service period, and provide a theoretical basis for the evaluation of the whole life performance of offshore isolated bridges, a performance degradation test of high-damping rubber bearings was firstly carried under the action of seawater dry-wet cycles, and a corresponding time-varying model of mechanical performance degradation was obtained. The time-varying parameters of mechanical performance of high-damping rubber bearings were given during the whole life cycle. Based on the degradation model of the mechanical performance of steel bar and concrete material, the time-varying parameters of steel bar and concrete were calculated during the whole life cycle. The time-varying law of flexural bearing capacity and ductility of pier section was analyzed during the full-life cycle under three working conditions, longitudinal reinforcement deterioration, stirrup deterioration and both deterioration. Subsequently, a nonlinear finite element model of offshore isolated bridge was established in SAP2000 software, and three working conditions were designed, including pier degradation, bearing degradation, pier and bearing degradation together. The time-varying law of bridge seismic responses were analyzed and compared under different conditions. The results show that the deterioration of stirrup leads to a significant decrease in ductility of the pier section, but has little effect on flexural bearing capacity of the section, while the deterioration of longitudinal reinforcement is on the contrary. The common deterioration of longitudinal reinforcement and stirrup makes the bending resistance and ductility of pier section significantly decrease. Separate deterioration of pier and bearing have effects on both pier response and hysteresis curve of bearing. Compared with the single deterioration of bearing performance and pier material, the joint action of two has the greatest influence on the seismic response of pier and bearing hysteretic curve. With the increase of service time, the displacement at the top of pier and bending moment-turn angle hysteretic area at the bottom of pier increases gradually, but the moment at the bottom of the pier and the hysteretic area of bearings decreases. The seismic performance of isolated bridge is greatly affected by extremely rare earthquakes. Under the extremely rare earthquakes, the seismic response of pier and bearing is significantly increased. 2 tabs, 19 figs, 23 refs.