Abstract

The most common tools in seismic performance assessment of highway bridges are single-variable fragility curves. However, fragility curves are not confidently reliable due to utilizing only a single intensity measure (IM). Alternatively, single- and multi-variable vulnerability functions, of which the latter is scarce and rather complex, have been proposed for that purpose, yet without considering the effects of the strong vertical component of near-field earthquakes. This study aimed to develop a multi-variable vulnerability function for multi-span continuous concrete box-girder bridges, accentuating near-field earthquakes. Ten bridge models corresponding to the 1971-1990 design era were considered and analyzed, subjected to three-component records of 164 earthquakes using OpenSees framework. First, 28 IMs related to horizontal and vertical ground motions, and 12 engineering demand parameters were utilized, and a set of potentially optimal IMs were determined through optimality investigation. Then, to ensure that identified IMs are authentically optimal candidates, Lasso regression was employed, introducing 12 IMs as optimal. Finally, Step-wise regressions were conducted to reduce the complexity of the proposed equation. Results revealed peak ground acceleration, peak ground velocity, and velocity spectrum intensity of the horizontal component of ground motion, and acceleration spectrum intensities of both horizontal and vertical components as optimal ones.

摘要

公路桥梁抗震性能评估中最常用的工具是单变量脆性曲线。然而，由于仅使用单一强度测量 (IM)，脆性曲线并不可靠。或者，为此目的提出了单变量和多变量脆弱性函数，后者稀缺且相当复杂，但没有考虑近场地震的强垂直分量的影响。本研究旨在为多跨连续混凝土箱梁桥开发多变量易损性函数，强调近场地震。考虑和分析了 1971-1990 年设计时代对应的 10 个桥梁模型，使用 OpenSees 框架对 164 次地震的三分量记录进行了分析。第一的，利用与水平和垂直地震动相关的28个IMs和12个工程需求参数，通过最优性调查确定了一组潜在的最优IMs。然后，为了确保识别出的 IM 是真正的最佳候选者，采用了 Lasso 回归，引入了 12 个 IM 作为最佳候选。最后，进行逐步回归以降低所提出方程的复杂性。结果表明，地震动水平分量的峰值地加速度、地速度峰值和速度谱强度，以及水平分量和垂直分量的加速度谱强度均为最优值。为了确保识别出的 IM 是真正的最佳候选者，采用了 Lasso 回归，引入了 12 个 IM 作为最佳候选。最后，进行逐步回归以降低所提出方程的复杂性。结果表明，地震动水平分量的峰值地加速度、地速度峰值和速度谱强度，以及水平分量和垂直分量的加速度谱强度均为最优值。为了确保识别出的 IM 是真正的最佳候选者，采用了 Lasso 回归，引入了 12 个 IM 作为最佳候选。最后，进行逐步回归以降低所提出方程的复杂性。结果表明，地震动水平分量的峰值地加速度、地速度峰值和速度谱强度，以及水平分量和垂直分量的加速度谱强度均为最优值。