Calibration of Analytical Fragility Curves Based on Empirical Data of Bridges
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摘要: 基于理论计算或试验研究定义桥梁损伤状态建立的理论易损性曲线,通常不能将桥梁构造(包括几何性质、材料性质等)、地面运动和场地条件等因素均考虑在内.鉴于此,为更加精确地以易损性曲线的形式评估桥梁抗震性能,首先利用1994年北岭地震桥梁损伤数据建立双参数对数正态分布的经验易损性曲线;其次,给出一种多跨桥梁力学模型,定义桥墩柱转动延性值量化桥梁损伤状态,获得4种损伤状态下的理论易损性曲线;最后,以90%置信区间的经验易损性曲线对理论易损性曲线进行校准.计算结果表明:利用桥梁力学模型建立的理论易损性曲线校准后能近似吻合经验易损性曲线,且3种损伤状态阈值由SRSS优化公式得到校准.随着结构损伤知识的进展,未来可利用更详细的结构损伤过程对校准后的理论易损性曲线做二次更新,进一步提高桥梁系统风险评估的精确性,尤其是遭受强震灾害下由多座桥梁组成的高速公路网络.Abstract: Most previous studies of analytical fragility curves based on bridge damage states defined through theoretical computations or experimental investigations couldn’t fully include the influences of bridge configuration (geometric properties, material properties, etc.), ground motion, site condition and so on. In view of this, the empirical fragility curves of the 2-parameter lognormal distribution were firstly constructed on the basis of the bridge damage data from the 1994 Northridge earthquake. Meanwhile, the analytical fragility curves of a multispan bridge model under four different damage states were obtained with definition of the bent column rotational ductility thresholds. Lastly, the analytical fragility curves were calibrated with the empirical fragility curves of the 90% confidence interval. The results show that the calibrated analytical fragility curves of the bridge model are fairly consistent with the empirical ones, and the threshold values of the 3 damage states are also calibrated with the SRSS optimization formula. With the progress of the structural damage knowledge, the calibrated analytical fragility curves can be updated again. The improved fragility curves are promising in the seismic risk assessment of a highway network containing as many as thousands of bridges that may be affected by a major earthquake nearby or far away.
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