动态子结构法在凸起地形地震动响应中的应用
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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.
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.
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.
引文
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[10]ZHANG W,CHEN X F.Traction image method for irregular free surface boundaries in finite difference seismic wave simulation[J].Geophysical Journal International,2006,7(1):337
[2] 荣棉水,李小军.局部地形对出平面运动谱特性的影响分析[J].中国地震,2007,23(2):147RONG Mianshui,LI Xiaojun.The effect analysis of topography on the spectrum property of anti-plane movement[J].Earthquake Research in China,2007,23(2):147
[3] 荣棉水,李小军,吕悦军.平台地形地面运动特征周期值的影响[J].中国地震,2009,25(2):178 RONG Mianshui,LI Xiaojun,LU Yuejun.Effect of protruding topography on characteristic period of ground motion[J].Earthquake Research in China,2009,25(2):178
[4] 刘晶波.局部不规则地形对地震地面运动的影响[J].地震学报,1996,18(2):239LIU Jingbo.Influence of local irregular topography on seismic ground motion[J].Acta Seismologica Sinica,1996,18(2):239
[5] 郝明辉,张郁山.凸起地形对地震动特性的影响[J].地震学报,2014,36(5):883HAO Minghui,ZHANG Yushan.Analysis of terrain effect on the properties of ground motion.Acta Seismologica Sinica,36(5):883
[6] GEORGE D,ACHILLEAS G.Numerical evaluation of slope topography effects on seismic ground motion[J].Soil Dynamics and Earthquake Engineering,2005,25:547
[7] 李英民,王丽萍,赵耀.岩质坡地建筑设计水平地震动放大系数的确定[J].地震工程与工程振动,2010,30(4):159LI Yingmin,WANG Liping,ZHAO Yao.Amplification factors of design horizontal ground motions for structures on rock slops[J].Earthquake Engineering and Engineering Dynamics,2010,30(4):159
[8] 梁建文,巴振宁.弹性层状半空间中凸起地形对入射平面SH波的放大作用[J].地震工程与工程振动,2008,28(1):1LIANG Jianwen,BA Zhenning.Surface motion of a hill in layered half-space subjected to incident plane SH waves[J].Earthquake Engineering and Engineering Dynamics,2008,28(1):1
[9] GE Z X,CHEN X F.An efficient approach for simulating wave propagation with the boundary element method in multilayered media with irregular interfaces[J].Bulletin of the Seismological Society of America,2008,98(6):3007
[10]ZHANG W,CHEN X F.Traction image method for irregular free surface boundaries in finite difference seismic wave simulation[J].Geophysical Journal International,2006,7(1):337