基于可靠度与易损性的地震动输入修正方法

Calibration of Seismic Input Parameter Based on Reliability and Fragility

在基于性能的地震工程理念与经典可靠度理论框架下,分析了地震易损性与结构可靠度的共同特性,阐释了将两者相结合的理论基础与概率方法;以一座三跨连续梁桥为例,基于OpenSees平台建立桥梁有限元模型,通过非线性动力时程分析对结构进行概率地震需求及易损性分析,基于易损性曲线考虑3种抗震目标对桥墩进行抗震设计,并对设计墩柱进行恒载与车辆活载作用下的可靠度分析;考虑不同地震重现期,根据泊松随机过程计算各类地震作用下的目标可靠度,基于概率方法对结构的初始可靠度进行修正,进一步结合地震易损性,确定不同抗震目标下的地震动水平,提出基于可靠度与易损性的地震动输入参数确定方法。结果表明,1000年、475年和50年地震重现期下,修正PGA均值分别为0.25 g、0.24 g和0.22 g,高于仅考虑易损性时的0.21 g。本方法将地震易损性与可靠度相结合,为结构不同层次的抗震设计提供了思路与方法。

Within the framework of Performance-Based Earthquake Engineering(PBEE)and classical reliability theory,this study reviews the common characteristics of seismic fragility and reliability,interpreting the theoretical foundation and probabilistic methods for their combination.In the case study,probabilistic engineering demand parameters and seismic fragility for a continuous girder bridge are first analyzed using non-linear dynamic time-history analysis.Then,three types of seismic performance objectives are considered for the seismic design of the pier.Additionally,reliability analysis is conducted considering dead load and vehicle live load.Various seismic return periods are set to calculate target reliability indexes according to the Poisson random process.This process calibrates the initial reliability index,which is then combined with the fragility curve using a probabilistic approach to determine seismic input parameters for different seismic performance objectives.The results show that the calibrated input parameters are 0.25 g,0.24 g,and 0.22 g for return periods of 1000,475,and 50 years,respectively.These values are slightly larger than the 0.21 g determined by the fragility curve alone.The proposed method simultaneously considers seismic fragility and reliability,providing a new approach for the seismic design of structures with varying seismic requirements.