高速铁路简支箱梁桥的概率地震需求模型及易损性分析

基于已建成高速铁路桥结构类型统计数据,以典型预应力混凝土简支箱梁桥为对象进行易损性研究。考虑5个不确定性参数,基于拉丁超立方抽样的反复试验法建立桥梁样本。采用"装箱法"选择地震动记录,与桥梁样本配对后进行非线性时程分析得到结构响应。定义各构件的损伤状态,通过对构件需求能力比进行二次回归建立桥梁各构件的概率地震需求模型,并生成构件易损性曲线,运用二阶单一边界法生成全桥易损性曲线。结果表明：二次回归分析产生的概率需求模型比线性回归方法更可靠;在地震作用下,此类桥梁构件中的墩柱、活动支座较易损伤,二阶单一边界法能较好地评估全桥系统易损性,在应用上二阶单一边界法比一阶上下边界法简洁方便。

Probabilistic seismic demand models and fragility estimates for multi-span simply supported railway box girder bridges

For the proposes of fragility analysis, a typical configuration of multi-span simply supported concrete box girder bridges are selected as analytical object from the statistics of as-built high-speed railway bridges in China. A set of bridge samples, in which five uncertain parameters are considered, are established using the trial and error method based on the Latin hypercube sampling. A portfolio of recorded ground motions divided into bins are assembled, and matched with bridge samples. Then nonlinear time history analyses are performed to capture the responses of structure. Damage states of bridge components are defined, and probabilistic seismic demand models are formulated by quadratic regression analysis for the ratios of the capacity and demand. Fragility curves of bridge components are developed consequently and the fragility of bridge system is evaluated using a single estimate for the second order bounds method. The results show that PSDMs formulated by quadratic regression are better than that by traditional linear regression. The expansion bearing and the column piers of this bridge type are fragile under earthquake excitation. A single estimate for the second order bounds method is preferable to evaluate the fragility of bridge system, and is easier to use than the first order bounds method.