基于条带-云图法的地震动持时对结构地震易损性影响分析

Investigation on effect of ground motion duration on seismic fragility of structures based on stripe-cloud approach

地震动持时对结构损伤的影响显著,然而目前地震易损性研究中很少考虑地震动持时的影响。本文提出了一种地震易损性分析的条带-云图法,引入向量型地震动强度指标IM=[IM1,IM2],利用IM1进行基于条带法的结构时程分析,然后采用与地震动持时相关的IM2离散化时程分析统计结果,进行云图法回归分析,建立合理考虑地震动持时影响的结构概率地震需求模型,进而分析地震动持时对结构地震易损性的影响。为了说明本文提出的方法,分别选取具有长、短持时特性的两组地震动作为输入,对3个高度不同的钢筋混凝土框架结构采用条带-云图法进行了地震易损性分析。分析结果表明:采用条带-云图法获得的IM与结构损伤之间的相关程度明显增加,可以提高概率地震需求模型的可靠性;与短持时地震动相比,长持时地震动可以在更低的强度水平引起更严重的结构损伤,在易损性分析中需要考虑持时影响;地震动持时对结构易损性分析结果的影响与选择的地震动强度指标有关,与能量相关的指标可以更好地反映地震动持时的影响。

Ground motion duration has significant influence on the damage of structures.Nevertheless,the impact of ground motion duration was rarely considered in seismic fragility analysis of structures currently.In this paper,the stripe-cloud approach was proposed to investigate the influence of ground motion duration on seismic fragility of structures.Vector-valued intensity measure(IM)of ground motion,IM=[IM1,IM2],was introduced.First,IM1 is used to perform time-history analysis of structures based on stripe method,and IM2 which relates to ground motion duration is used to discretize the statistical results of the time-history analysis.Then cloud method is adopted further to establish the probabilistic seismic demand models for structures which can consider the influence of ground motion duration reasonably.Furthermore,two suites of ground motion records with long-and short-duration were chosen as inputs respectively,and stripe-cloud approach was conducted for 3 reinforced concrete frame structures which have varying heights.The results demonstrate that stripe-cloud approach not only dramatically increases the correlation between seismic intensity measures and structural damage measures,but also improves the reliability of the probabilistic seismic demand models of structures.Vector-valued IM can effectively consider the effect of duration on seismic fragility analysis.Long-duration ground motion can cause severer damage at lower intensity levels comparing to short-duration ground motion.It is necessary to explicitly consider the effect of ground motion duration in seismic fragility analysis.The influence of ground motion duration on the seismic fragility analysis results is also related to the IM selected.Energy-related IMs can consider the influence of duration appropriately.