非规则平行匝道桥部分减隔震体系地震响应与减震机理

Seismic Response and Isolation Mechanism of Partially Isolated System for Irregular Parallel Ramp Bridges

针对非规则平行匝道桥的合理抗震体系问题,研究了部分减隔震体系的地震响应与减震机理.建立结构动力响应非线性有限元模型,对比了采用延性体系、减隔震体系以及部分减隔震体系的桥梁地震响应.结果显示部分减隔震体系能有效降低平行匝道因墩高差异而引起的主梁整体转动效应,并对包括主梁加速度、墩底弯矩、墩柱漂移率以及最不利单桩响应等具有更好的减震功效.基于规则桥梁的单自由度简化方法对3种体系进行了平转动比的定性评估,显示非规则平行匝道桥受多阶振型共同作用明显,进一步的幅频分析显示部分减隔震体系的动力响应在各振型间更趋于平均化.对3种体系各构件性能项以及结构整体的地震冗余度指标进行了比较,结果显示部分减隔震体系能有效避开导致延性抗震体系和减隔震体系取得最小冗余度指标的参数区域,因而具有最高的冗余度指标.

To explore a reasonable earthquake resisting system for irregular parallel ramp bridges, the seismic response and isolation mechanism of the partially isolated system were investigated.Nonlinear finite element models were established and the seismic responses of the bridge using ductile, fully isolated and partially isolated systems were compared.The results show that the partially isolated system can effectively reduce the unexpected rotation of the girder caused by the evident difference in pier heights and achieve better isolation effect in terms of acceleration of the girder, base bending moment, drift ratio of the piers and the seismic force to the critical piles.Based on the simple single-degree-of-freedom method of the regular bridge, a qualitative evaluation on the ratio of the translational displacement to rotation of the deck of the three systems was conducted;the results show that the dynamic response of the irregular ramp bridge are dominated by multiple modes.Further analysis on the amplitude-frequency relationship shows that the partially isolated system tends to perform a more averaged dynamic response among the modes.The seismic redundancy indices of individual component performance and the entire structure were also analyzed.The results show that the partially isolated system can avoid the parameters that had led to minimum redundancy of both the ductile system and the isolated system and consequently resulted in the highest redundancy.