城市密集建筑群对沉积谷地地震动放大效应的影响

Influence of Urban Intensive Building Groups on the Ground Motion Amplification Effect of an Alluvial Valley

采用有限元模拟方法建立了建筑群-沉积谷地二维模型,并在土体截断边界上施加粘弹性人工边界,在频域与时域中对比分析此体系和单独沉积谷地的地震反应,观察地震时沉积谷地与建筑群之间的动力相互作用规律。分析表明,沉积谷地中建筑群对谷地本身的地震反应具有显著影响。入射波频率较低时,由于共振效应的存在,在部分区域处建筑群-沉积谷地体系的地表位移响应幅值会大于单独沉积谷地,但随着入射波频率的增加,建筑群的存在又会对地震反应产生明显的减弱效果;建筑群对谷地的影响还与建筑高度和建筑间距有关,且不同位置处的响应也存在很大差异。计算结果可为沉积谷地中设防烈度的设置以及工程抗震设计提供部分理论依据。

A two-dimensional model of a buildings-alluvial valley system is established using the finite-element method,and the viscoelastic artificial boundary is applied on the truncated boundary of the soil body.By comparing and analyzing the seismic responses of the buildings-alluvial valley system and the single alluvial valley both in the frequency domain and the time domain,the dynamic interaction between alluvial valley and buildings under earthquake is studied.The results show that because of the resonance effect under low-frequency incident waves,the surface displacement response amplitude of the buildings-alluvial valley system is larger than that of the single alluvial valley in some areas.As the frequency of the incident wave increases,the buildings will have a significant weakening effect on the seismic response.In addition,the impact of the buildings on the valley is also related to the building height and building spacing,and the responses at different locations are significantly different.The numerical results can provide a theoretical basis for the setting of fortification intensity in alluvial valleys and the seismic design of projects.