确定性地震动空间差异对重力坝地震响应影响研究

针对高坝-地基体系地震响应分析对空间差异地震动场的需求,在波动输入模型基础上引入地震波组合效应提出确定非一致地震动场模型。该模型从地震动场形成的物理机制出发,以模拟确定性地震动空间差异为目标构建非一致地震动场。随后以确定非一致地震动场和波动输入对应地震动场为基础,采用重力坝算例研究确定性地震动空间差异对结构地震响应的影响。结果显示,相对于波动输入模型,确定非一致地震动场模型可在内蕴多点多维地震动相关性基础上模拟地震动的时间滞后、复杂幅值变化、时程形状差异等宏观空间差异特征。与波动输入地震动场相比,确定非一致地震动场引起重力坝坝踵主拉应力峰值增加的算例占比66.4%,引起下游折坡主拉应力峰值增加的算例占比76.7%。在主拉应力峰值平均值方面,确定非一致地震动场引起坝踵和下游折坡处的最大增幅分别为25.3%和46.4%。考虑工程安全,高坝-地基体系的非一致地震响应分析须全面考虑确定性地震动空间差异的影响。

Influence of deterministic spatial variation of motions on seismic response of gravity dam

For meeting the demand of non-uniform seismic response analysis of high dam-foundation sys-tem,a new deterministic non-uniform seismic motion field (DNSMF) model based on wave input model by introducing the combination effect of seismic waves is proposed in this paper. The combination effect of seis-mic waves is used to illustrate the formulate mechanism of DNSMF. Then the influence of DNSMF on seis-mic response of gravity dam is investigated by two cases of which motion field gained respectively by DNS-MF model and vertical incident wave input model. The result shows that the DNSMF could be gained con-taining the correlation of multi-support and multi-dimension motions. And the macro features of seismic mo-tion field such as time delay,complex amplitude variation and shape change of motion time history,could be expressed by DNSMF model. And the seismic response of gravity dam is influenced dramatically by DNS-MF compared with motion field of vertical incident wave model. The percentage of increasing cases is 66.4% according to principle stress in dam heel and is 76.7% according to principle stress in downstream slope change. Under the influence of DNSMF,the mean value of peak principle stress increases dramatical-ly with the maximum increase of 25.3% in dam heel and 46.4% in downstream slope change respectively. For the safety of project, the deterministic spatial variation of motion should be fully considered in the non-uniform seismic response analysis of high dam-foundation system.