复杂地形条件下地震波的传播研究
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摘要
利用显式有限元结合透射人工边界,研究了典型山谷地形桥址对地震波传播的影响,探讨了不同入射角度、入射方向及山谷跨度对地震动地形效应的影响规律。结果表明:坡底各位置的地震动的反应相差不大,而坡顶及坡顶后一定范围内的地震动存在不同程度的放大;地震波垂直入射时引起的地表放大效应最大,山谷左右两侧地表放大效应相对相差不大;在计算桥梁结构的地震反应时可以仅考虑地震波垂直入射的情况,其结果是偏安全的;地形放大效应存在明显的方向性;山谷的放大作用和山间跨度密切相关。
Seismic wave propagation in a typical mountain-valley bridge site was studied based on the explicit finite element method with artificial transmitting boundary.The topographic effects of the incident degrees,the incident directions and the span of the mountain-valley were also discussed.It was shown that the amplification effects at the bottom of slopes did not change obviously.However,the effects near the top of slope were magnified to some extent.The absolute amplification factors were the largest under the condition of normal incidence,and the difference of the relative amplification factors at the left and right sides was not obvious.The normal incidence condition could be considered and the results were safe.Meanwhile,there was obvious directivity of topographic effects.The amplification effects were related to the span of mountain-valley.
Seismic wave propagation in a typical mountain-valley bridge site was studied based on the explicit finite element method with artificial transmitting boundary.The topographic effects of the incident degrees,the incident directions and the span of the mountain-valley were also discussed.It was shown that the amplification effects at the bottom of slopes did not change obviously.However,the effects near the top of slope were magnified to some extent.The absolute amplification factors were the largest under the condition of normal incidence,and the difference of the relative amplification factors at the left and right sides was not obvious.The normal incidence condition could be considered and the results were safe.Meanwhile,there was obvious directivity of topographic effects.The amplification effects were related to the span of mountain-valley.
引文
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[2]王君杰,王前信,江近仁.大跨拱桥在空间变化地震动下的响应[J].振动工程学报,1995,18(2):119–126.(WANG Jun-jie,WANG Qian-xin,JIANG Jin-ren.Random response of long-span arch bridge under spatially variable seismic excitations[J].Journal of Vibration Engineering,1995,18(2):119–126.(in Chinese))
[3]NAZMY Aly S,ABDEL G,AHMED M.Nonlinear earthquake response analysis of long-span cable-satyed bridgest:heory[J].Earthquake Engineering&Structural Dynamics,1990,19(1):45–62.
[4]刘洪兵,范立础.大跨桥梁考虑地形及多点激励的地震响应分析[J].同济大学学报,2003,31(6):641–646.(LIU Hong-bing,FAN Li-chu.Seismic analysis of long span bridges considering topographic effects and multi-supported excitations[J].Journal of Tongji University,2003,31(6):641–646.(in Chinese))
[5]HARTZELL S H,CARVER D L,KING K W.Initial investigation of site and topographic effects at Robinwood Bridge,California[J].Bull Seis Soc Am,1994,84(5):1336–1349.
[6]ASHFORD S A,SITAR N.Analysis of topographic amplification of inclined shear waves in a steep coastal bluff[J].Bull Seis Soc Am,1997,87:692–700.
[7]ASHFORD S A,SITAR N,LYSMER J,DENG N.Topographic effects on the seismic response of steep[J].Bull Seis Soc Am,1997,87:701–709.
[8]李小军,廖振鹏,关慧敏.粘弹性场地地形对地震动影响分析的显式有限元–有限差分方法[J].地震学报,1995,17(3):362–369.(LI Xiao-jun,LIAO Zhen-peng,GUAN Hui-min.An explicit finite element-finite difference method for analyzing the effect of visco-elastic Local topography on the earthquake motion[J].Acta Seismologica Sinica,1995,17(3):362–369.(in Chinese))
[9]YANG Jun,SATO T.Interpretation of seismic vertical amplification observed at an array site[J].Bull Seis Soc Am,2000,90(2):275–285.
[10]CELEBI M.Topographic and geological amplification determined from strong-motion and after shock records of the 3 March 1985 Chile Earthquake[J].Bull Seis Soc Am,1987,77:1147–1167.
[11]廖振鹏.工程波动导论[M].第二版.北京:科学出版社,2002.(LIAO Zhen-peng.Engineering wave theory[M].2nd ed.Beijing:Science Press,2002.(in Chinese))
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