大跨度整体式高墩桥梁地震易损性分析

Seismic Vulnerability Analysis of Long-span Integral High-pier Bridges

为探究强震作用下高墩大跨整体式桥梁的地震损伤机理,从基于性态的抗震设计理念出发并结合概率方法对其进行地震易损性研究。首先基于OpenSees建立实例桥的弹塑性分析模型;然后综合考虑地震动与桥梁结构参数的双随机特性,生成地震动与桥梁的随机样本,并进一步采用IDA法建立桥梁概率性地震需求模型,确定桥墩各构件的地震易损性;最后基于条件概率原理,考虑桥墩的4种构件失效模式,结合PCM法快速、有效地推导出精确的桥梁系统地震易损性。研究表明:薄壁边墩墩顶截面的曲率延性随PGA发展较快,能提前进入塑性状态并成为桥墩各构件的最易损截面;在设计地震和罕遇地震作用下,发生中等破坏的失效概率分别为0.38和0.93,而中墩截面的抗震性能明显优于边墩截面,在罕遇地震下发生中等破坏的失效概率仅为0.15;与一阶界限法相比,PCM法能充分考虑各构件之间的相关程度,利用其导出考虑多种失效模式下复杂体系桥梁的系统易损性曲线更为合理。

In order to explore the seismic damage mechanism of integrated bridges with high pier and large span under strong earthquakes,the seismic vulnerability of bridges was studied based on the concept of performance-based seismic design and probability method.First of all,the elastic-plastic analysis model of the bridge example was established based on OpenSees code.Subsequently,by comprehensively considering the double random characteristics of ground motion and bridge structural parameters,the random samples of ground motion and bridge were generated.Meanwhile,the probabilistic seismic demand model of bridge was established by IDA method,and the seismic vulnerability of each component of the pier was determined.Finally,based on the principle of conditional probability,considering four failure modes of piers,and combined with PCM method,the accurate seismic vulnerability of the bridge system was established quickly and effectively.The results showed that the curvature ductility of the top section of the thin-walled side pier developed rapidly with PGA,this section could enter the plastic state in advance,and became the most vulnerable section of each member of the pier;Under design earthquake and rare earthquake,the failure probability of moderate damage was 0.38 and 0.93 respectively,while the seismic performance of middle pier section was obviously better than that of side pier section,and the failure probability of moderate damage under rare earthquake was only 0.15.Compared with the first-order boundary method,PCM method could fully consider the correlation between components.Therefore,it is more reasonable to use PCM to establish the system vulnerability curves of complex system bridges considering multiple failure modes.