动态子结构法在凸起地形地震动响应中的应用

Application of dynamic substructure method to protruding topography on characteristics of ground motion

摘要:

为研究山地地形对地震动放大效应的影响,满足实际工程中山地建筑地震动设计的需要,以单峰凸起地形为例,引入动态子结构法,计算地形坡角在30~60°,凸起高度20~80 m和平台段宽度50~600 m共60个不同尺寸岩质凸起地形在地震动输入下的响应,得到不同尺寸凸起地形下模型各点加速度和频谱特性变化规律.结果表明:与传统有限元分析方法相比,动态子结构法在保证计算精度的同时,能很大程度提高计算效率；凸起地形对地震动放大效应影响较大,坡脚到坡顶地震动响应不断增大,坡顶平台中点放大效应最为明显；随地形坡角和坡高增加,地形对地震动的放大效应呈增大趋势；坡角和坡高一定时,随地形宽度增加,地形凸起高度较小时,地震放大效应呈增大趋势,反之凸起高度较大时,地震放大效应呈降低趋势；地形凸起尺寸的增加会激发高频段反应的加剧,同时降低低频段反应峰值.

Abstract:

To study the effect of mountain topography on seismic amplification and meet the seismic design needs of mountain building in practical engineering, taking unimodal protruding topography as an example, dynamic substructure method was introduced to calculate the seismic response of 60 different-size rock bump terrains with slope angle of 30 ~ 60°, bump height of 20 ~ 80 m, and platform width 50 ~ 600 m under the ground motion input, and the seismic response law of amplification of different-size rock bump terrains was obtained. Results show that the dynamic substructure method can greatly improve the computation efficiency while ensuring the computation accuracy. The convex topography has a great influence on the amplification effect of ground motion. The response of ground motion increases constantly from base of slope to slope top, and the amplification effect of the central point of the platform is the largest. With the increase of slope angle and height, the amplification effect of topography on ground motion increases. When the slope angle and slope height remain unchanged and the topographic relief height is relatively small, as the topographic width increases, the seismic amplification effect increases; otherwise, when the bump height is larger, the seismic amplification effect decreases. The increase of topographic relief size leads to the intensification of high frequency response and the decrease of low frequency response peak.