This study conducts seismic risk assessment of highway bridges in western Canada. The performance-based earthquake engineering (PBEE) framework is enhanced to assess the expected annual repair cost ratio (ARCR) and annual restoration time (ART) of a benchmark bridge class under the region’s three types of earthquakes - shallow crustal earthquakes (CEs), deep subcrustal earthquakes (SCEs), and megathrust Cascadia subduction earthquakes (CSEs). First, event-specific seismic hazard models are considered, whereas event-consistent ground motions are selected for non-linear time history analyses. Compared with those from CEs and SCEs, CSE ground motions feature a much longer duration. This long-duration effect is captured by validating the numerical model of the bridge column against (1) a cyclic pushover test under standard versus long-duration loading protocols and (2) a shaking table test excited by six consecutive ground motions. Besides, the Park and Ang damage index is utilized as the column’s engineering demand parameter (EDP) and updated as a demand-capacity ratio model when reaching four different damage states. A comprehensive list of ground motion intensity measures (IMs) is considered where the spectra acceleration at one second, (1.0), is chosen as the most suitable IM based on its performance in proficiency, efficiency, practicality, and EDP-IM correlation across all three earthquake events. Subsequently, component- and system-level fragility models are derived under each earthquake type using the analysis that convolves the seismic demands with capacity models for multiple bridge components. To further quantify and propagate the epistemic uncertainty associated with the development of probabilistic seismic demand models (PSDMs), the bootstrap resampling technique is utilized to generate numerous seismic demand datasets and develop a stochastic set of seismic fragility curves. Finally, the bootstrapped, event-dependent fragility models are combined with the respective hazard models and probabilistic loss functions to assess the expected ARCR and ART for the benchmark bridge class. This study underscores the significantly higher seismic risk of highway bridges when facing CSEs, followed by CEs and SCEs.

中文翻译：

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加拿大西部公路桥梁在地壳、地壳下和俯冲地震作用下的地震风险评估

本研究对加拿大西部公路桥梁进行地震风险评估。基于性能的地震工程（PBEE）框架得到增强，以评估该地区三种类型地震（浅地壳地震（CE）、浅层地壳地震（CE）、深部地壳地震（SCE）和巨型逆冲卡斯卡迪亚俯冲地震（CSE）。首先，考虑特定事件的地震灾害模型，而选择事件一致的地面运动进行非线性时程分析。与CE和SCE相比，CSE地震动的持续时间更长。这种长期效应是通过验证桥柱的数值模型来捕获的：（1）标准与长期加载协议下的循环推覆测试和（2）由六次连续地面运动激发的振动台测试。此外，Park和Ang损伤指数被用作柱的工程需求参数（EDP），并在达到四种不同损伤状态时更新为需求能力比模型。考虑了地震动强度测量 (IM) 的综合列表，其中一秒的频谱加速度 (1.0) 被选为最合适的 IM，基于其在熟练程度、效率、实用性以及所有测量中的 EDP-IM 相关性方面的表现。三起地震事件。随后，通过将地震需求与多个桥梁构件的能力模型进行卷积分析，得出每种地震类型下的构件和系统级易损性模型。为了进一步量化和传播与概率地震需求模型（PSDM）开发相关的认知不确定性，利用自举重采样技术生成大量地震需求数据集并开发一组随机地震脆弱性曲线。最后，将自举的事件相关脆弱性模型与各自的危险模型和概率损失函数相结合，以评估基准桥梁类别的预期 ARCR 和 ART。这项研究强调了公路桥梁在面对 CSE 时的地震风险显着更高，其次是 CE 和 SCE。