SV波入射下河谷地形地震动分布特征分析
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摘要
基于显式有限元方法和人工透射边界,对二维河谷地形在3条地震动波以SV波形式垂直入射和30°斜入射下进行了地震反应分析,比较了河谷地表各观测点地震动的差别,探讨了河谷地形地震动空间分布特征。结果表明,河谷地形对地震动分布具有重要影响,沿河谷斜坡顶到谷底的各观测点地震动峰值加速度(PGA)存在显著差异,地震动位移存在差动现象,地震动加速度反应谱在大于1 Hz的高频段差别明显。入射角度是影响场地地震反应的重要因素,斜入射时各观测点PGA和相对位移的离散程度明显大于垂直入射情形。
Using explicit finite element method and artificial transmitting boundary,the seismic response analysis of a 2D canyon model is performed under three incident SV seismic waves respectively with the assumptions of vertical incidence and oblique incidence at the angle of 30 degrees.The canyon surface ground motions have been compared and the distribution characteristics of ground motions are summarized.It indicates that canyon topography has significant influence on the distribution of ground motions.The peak ground accelerations(PGA) vary greatly from the bottom of the slope to the upper corners.Ground acceleration at high frequency band beyond 1 Hz has been more greatly amplified.And the canyon ground surface has been characterized by relative displacements(RD).It is also found that the incidence angle shows significant influences on the ground motions.Under oblique incident SV waves,the discrete degree of the PGA and RD observed at the canyon surface are much larger than that under vertical incident SV waves.
Using explicit finite element method and artificial transmitting boundary,the seismic response analysis of a 2D canyon model is performed under three incident SV seismic waves respectively with the assumptions of vertical incidence and oblique incidence at the angle of 30 degrees.The canyon surface ground motions have been compared and the distribution characteristics of ground motions are summarized.It indicates that canyon topography has significant influence on the distribution of ground motions.The peak ground accelerations(PGA) vary greatly from the bottom of the slope to the upper corners.Ground acceleration at high frequency band beyond 1 Hz has been more greatly amplified.And the canyon ground surface has been characterized by relative displacements(RD).It is also found that the incidence angle shows significant influences on the ground motions.Under oblique incident SV waves,the discrete degree of the PGA and RD observed at the canyon surface are much larger than that under vertical incident SV waves.
引文
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[2]CELEBI M.Topographic and geological amplificationdetermined from strong motion and aftershock records ofthe 3 March 1985 Chile Earthquake[J].Bulletin of theSeismological Society of America,1987,77:1147-1167.
[3]梁建文,严林隽,LEE V W.圆弧形凹陷地形表面覆盖层对入射平面SV波的影响[J].地震学报,2001,23(6):622-636.LIANG Jian-wen,YAN Lin-jun,LEE V W.Effects of aCovering Layer in a circuilar-arc canyon on incidentplane SV waves[J].Acta Seismologica Sinica,2001,23(6):622-636.
[4]袁晓铭.圆弧状沉积盆地与软土单覆盖层出平面地表运动对比[J].地震工程与工程振动,2002,22(4):16-21.YUAN Xiao-ming.Comparison of out-of-plane surfaceground motion between a circular-arc alluvial valley and asingle overburden soft layer[J].Earthquake Engineeringand Engineering Vibration,2002,22(4):16-21.
[5]LOUSE G,PIERRE-YVES B,BEATRICE J.The effectof topography on earthquake ground motion:A reviewand new results[J].Bulletin of the Seismological Societyof America,1988,78(1):42-63.
[6]RASSEM M,GHOBARAH A,HEIDEBRECHT A C.Site effects on the seismic response of a suspensionbridge[J].Engineering Structures,1996,18(5):363-370.
[7]STEWART J P,SHOLTIS S E.Case study of strongground motion variations across cut slope[J].SoilDynamics and Earthquake Engineering,2005,25:539-545.
[8]LEE SHIANN-JONG,KOMATITSCH DIMITRI,HUANG BOR-SHOUH,et al.Effects of topography onseismic-wave propagation:An example from NorthernTaiwan[J].Bulletin of the Seismological Society ofAmerica,2009,99(1):314-325.
[9]Eurocodes Committee,Scientific and Technical.Eurocode8:Design of structures for earthquake resistance:Part 2:Bridges[S].Brussels:Cyprus Organisation forStandardisation,1995.
[10]中华人民共和国交通部.JTG/T B02-01-2008公路桥梁抗震设计细则[S].北京:人民交通出版社,2008.
[11]李小军,廖振鹏,关慧敏.黏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.Anexplicit finite element-finite difference method foranalyzing the effect of visco-elastic Local topography onthe earthquake motion[J].Acta Seismologica Sinica,1995,17(3):362-369.
[12]廖振鹏.工程波动理论导论(第二版)[M].北京:科学出版社,2002.
[13]李山有,马强,武东坡,等.断层场地地震反应特征研究[J].地震工程与工程振动,2003,23(5):32-37.LI Shan-you,MA Qiang,WU Dong-po,et al.Study ofcharacteristics of seismic responses of fault site[J].Earthquake Engineering and Engineering Vibration,2003,23(5):32-37.
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