上盘效应对工程结构位移反应影响分析

在断层附近的一定区域内,受到上盘效应等因素影响的地震动将显著改变结构的动力响应.针对上盘效应及与其相对的下盘效应对结构弹性及非弹性位移反应的影响进行研究.结果表明,上盘效应对(结构绝对位移的增大作用)在短周期段显著,下盘效应的增大作用在长周期段显著.尽管上盘地震动加速度峰值普遍较大,但其相对非弹性位移仅在长周期段大于下盘地震动,在短周期及中等周期段均较下盘地震动小.与远场地震动相比,在某些情况下受上盘和下盘效应影响的地震动将引起大的结构相对非弹性位移,因此将现有经远场地震动得出的相对非弹性位移关系用于近场区结构的性能评估会得到不安全的结果.

A study on the displacement response of structures due to hanging wall effects

The response of structure in the region near an active fault is dramatically influenced by the near-field effects,such as the hanging wall.In this paper,the characteristics of elastic and inelastic displacement response of structure due to these effects are investigated.According to this study,the amplification of absolute displacement response of hanging wall effects is significant in the short period range,while that of the foot wall effects is significant in the long period range.Although high peak ground accelerations are observed on hanging wall stations,the relative inelastic displacement response of the hanging wall ground motions is larger than foot wall ground motions only in very long period range.Larger relative inelastic displacement response is found in the short and medium period ranges of the foot wall effects.Compared with far-field ground motions,the high relative inelastic displacement capacity is needed when ground motions are influenced by hanging wall and foot wall effects.In some cases,unsafe results may be obtained in the evaluation of existing structures located in near-field regions when the relations of relative inelastic displacement is adopted for far-field ground motions.