基于性能的桥梁抗震设计中考虑持时的实际地震波优化选择方法

摘要

The duration of earthquake ground motions has insignificant effects on analysis results for performance-based seismic design of bridges (PBSD ).The incremental dynamic analysis of a six span reinforced concrete (RC ) continuous girder bridge was performed for decoupling the influence between duration,frequency spectrum and amplitude of structural seismic responses by using several groups of real and artificial earthquake waves matching the same target response spectrum and having different probability distributions with 5 -95%significant duration.The correlation between duration and seismic demanded of the RC girder bridge revealed that the mean,dispersion and probability distribution of duration of earthquake ground motions have little influence on displacement engineering demand parameters (EDP)but important effects on the probabilistic estimation (mean),dispersion and probability distribution of energy EDPs or fatigue failure and cumulative damage parameters;if energy EDPs are used in PBSD,the mean,dispersion and probability distribution of duration of earthquake ground motions must be in accordance with the real seismic hazard at the bridge site. An optimal method to rationally select real earthquake ground motions for PBSD based on the total probability theorem was presented,it could effectively consider the effects of mean,dispersion and probability distribution of duration on seismic demands of bridge structures and significantly improve the precision of analysis results and computation efficiency.%在基于性能的桥梁抗震设计（PBSD）中，是否考虑持时的效应会显著影响到分析结果的精确性。为了将持时与幅值、频谱的影响进行解耦，选择多组匹配同一目标谱的实际地震波和人工波，并使各组地震波的5－95％显著持时服从不同的概率分布，对一座钢筋混凝土连续梁桥进行IDA分析。对比持时与桥梁结构地震需求的相关性表明：持时的均值、离散度及其概率分布对于位移工程需求参数（EDP）影响较小，但对能量EDP以及包含能量项的疲劳破坏和累积损伤参数的概率预计（均值）、离散度及其概率分布影响显著。因此，在PBSD中如采用能量EDP，则必须考虑到所选地震波的持时均值、离散度及其概率分布均要符合工程场地实际的地震危险性。在此基础上，针对基于全概率理论的PBSD，提出一种能够考虑持时均值、离散度及其概率分布影响的实际地震波优化选择方法，能够显著提高分析结果的精确性和计算效率。