ABSTRACT

This paper proposes an alternative time-dependent seismic fragility assessment framework considering the variable correlation of structural random parameters for aging highway bridges subject to non-uniform chloride-induced corrosion attacks. The proposed systematic framework is implemented to perform a probabilistic time-dependent seismic fragility assessment for a typical multi-span reinforced concrete continuous girder (MSRCCG) bridge. Effects of non-uniform chloride-induced deterioration on the time-evolving seismic capacity, seismic demand of reinforced concrete (RC) columns, and the time-dependent seismic fragility of the case-study bridge are investigated using nonlinear sectional moment-curvature and nonlinear time history analysis. Furthermore, this paper performs comparative studies to investigate the influence of variable correlation of structural random parameters on the time-variant seismic capacity, seismic demand of RC columns, and time-dependent seismic fragility of the case-study bridge. The results indicate the following conclusions: (1) Non-uniform chloride-induced corrosion may change the vulnerable position and the damage mechanisms of RC columns; (2) Due to non-uniform chloride-induced deterioration, the flexural capacity and curvature ductility of RC columns may exhibit a nonlinear reduction, while there is a nonlinear accelerated growth of time-dependent seismic fragility for aging highway bridges along their service lives; (3) The time-variant seismic capacity (i.e., the flexural capacity and curvature ductility) and seismic demand of RC columns tends to have a certain reduction and increase by ignoring the variable correlation of structural random parameters, respectively; and (4) The time-dependent seismic vulnerabilities of aging highway bridges may be overestimated by ignoring the variable correlation of structural random parameters.

摘要

本文提出了一种替代的时间相关地震脆弱性评估框架，考虑到老化公路桥梁的结构随机参数的可变相关性，这些桥梁受到非均匀氯化物引起的腐蚀攻击。所提出的系统框架被实施以对典型的多跨钢筋混凝土连续梁 (MSRCCG) 桥进行概率时间相关的地震脆弱性评估。使用非线性截面弯矩曲率和非线性研究了非均匀氯化物引起的劣化对随时间演变的抗震能力、钢筋混凝土 (RC) 柱的抗震需求以及案例研究桥梁的时间相关地震脆弱性的影响时间历史分析。此外，本文通过对比研究研究了结构随机参数的可变相关性对案例研究桥梁的时变抗震能力、RC柱的抗震需求和时变地震脆弱性的影响。结果表明如下结论：（1）非均匀氯化物腐蚀可能改变RC柱的易损位置和损伤机制；（2）由于氯离子引起的非均匀劣化，RC柱的抗弯承载力和曲率延性可能呈现非线性减小，而老化公路桥梁在其使用寿命期间随时间地震脆性非线性加速增长；(3) 时变抗震能力（即，忽略结构随机参数的可变相关性，RC柱的抗弯承载力和曲率延性）和抗震需求趋于有一定的减少和增加；(4) 忽略结构随机参数的可变相关性，可能会高估老化公路桥梁的时间相关地震脆弱性。