近断层地震作用下考虑P-Δ效应的混凝土结构响应分析

Response Analysis of Concrete Structure Considering the P-Δ Effect due to Near-fault Earthquake Ground Motions

近断层地震动具有更大的水平地震和竖向地震作用,从而改变结构的p-Δ效应。首先,利用537组近断层地震动,统计分析了近断层地震动的反应谱特性和竖向与水平向加速度峰值比,考察了近断层地震动的特性。其次,分别对近断层脉冲地震动、近断层非脉冲地震动和远断层地震动作用下混凝土结构的弹塑性反应进行了计算,分析了p-Δ效应的影响规律。最后,同时输入竖向和水平向地震动,考虑竖向地震动对结构p-Δ效应的影响。结果表明:近断层地震动有较大的水平向和竖向反应谱值,在近断层区域,将竖向地震动作用简单的按照现行规范中的取水平地震作用的2/3进行考虑是偏于不安全的;加速度峰值一致的前提下,结构在近断层脉冲地震作用下具有较大的响应,但p-Δ效应对结构的响应影响不明显,幅度大多未超过10%;由于地震动的随机性及复杂性,竖向地震动引起的惯性力不一定会增大结构的反应,也有可能会减小结构的反应。

The p-Δ effect of structure will changed,because the near-fault earthquake ground motions has greater horizontal and vertical earthquake effect.First,the statistical analysis of the ratios of vertical-to-horizontal acceleration response spectrum and vertical-to-horizontal peak acceleration from 537 series of earthquake records will exhibit the characteristics of near-fault earthquake ground motions.Secondly,we conduct the elastic-plastic analyze of concrete structure with the p-Δeffect under near-fault ground motions with velocity impulse and near-fault ground motions and far-fault ground motions,analyse the influence of p-Δeffect.Finally,we consider horizontal and vertical ground motion at the same time,analyse the influence of p-Δeffect with vertical ground motion.Results indicate that near-fault earthquake ground motions have greater response spectrum value than usual,and it＇s unsafe to take vertical ground motion as 65 percent of horizontal ground motion in near-fault regions.Structure has greater earthquake response under near-fault ground motions with velocity impulse in the case of same peak acceleration value.But it＇s not obvious that structure response has p-Δeffect.Due to the randomness and complexity ofground motions,the inertial force caused by vertical ground motions can increase the response of structure and may also reduce the response of structure.