汶川地震竖向地震动特征初步分析
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摘要
选择国家强震动台网中心发布的2008年5月12日汶川地震四川、甘肃、陕西等地台站中的94组加速度记录进行了处理,提取了一些主要地震动参数,应用统计分析方法重点对地震动竖向与水平峰值加速度比、竖向与水平加速度反应谱及竖向与水平卓越周期比等进行了研究。结果表明:竖向与水平峰值加速度比的平均值为0.58,但约30%台站的峰值加速度比大于2/3;竖向与水平峰值加速度比随震中距的增大减小,近震区该比值离散性较大,场地条件对该比值也有较大的影响;在周期0~6s内竖向与水平加速度反应谱比曲线总体呈马鞍形;不同的周期段,竖向加速度反应谱和水平加速度反应谱的谱形有较大差异,相比水平加速度反应谱,竖向加速度反应谱偏"瘦";除少数台站外,绝大部分台站竖向与水平卓越周期比均小于1.0,该比值随震中距的增大而增大,并逐渐趋于平缓。上述研究结果可以为时程分析选取竖向地震动输入提供参考。
94 suites of acceleration records from the stations in Sichuan,Gansu and Shaanxi provinces during the Wenchuan earthquake of May 12,2008,which were released by China Strong Motion Networks Center,were selected to the process for extracting some essential ground motion parameters.The ratios of vertical to horizontal peak ground accelerations,the acceleration response spectra and predominant period were mainly investigated with the method of statistical analysis.The results indicated that the average ratio of vertical to horizontal peak ground motion is 0.58,and the ratios of more than 30% stations are greater than 2/3.This ratio decreases with the increasing epicentral distance and it is much discrete in the near-fault region.Furthermore,site condition also influences this ratio.The curve of vertical to horizontal acceleration response spectrum ratios with periods from 0 to 6 second appears to be saddle-shaped generally.The shapes of vertical and horizontal acceleration response spectrum vary within different period ranges.And vertical acceleration response spectrum looks thin comparing to the horizontal counterpart.Except several stations,the ratio between vertical to horizontal predominant periods is less than 1.0.This ratio increases with the increasing epicentral distance and becomes smooth gradually.The study results can provide a reference for choosing the vertical ground motion input during a time history analysis.
94 suites of acceleration records from the stations in Sichuan,Gansu and Shaanxi provinces during the Wenchuan earthquake of May 12,2008,which were released by China Strong Motion Networks Center,were selected to the process for extracting some essential ground motion parameters.The ratios of vertical to horizontal peak ground accelerations,the acceleration response spectra and predominant period were mainly investigated with the method of statistical analysis.The results indicated that the average ratio of vertical to horizontal peak ground motion is 0.58,and the ratios of more than 30% stations are greater than 2/3.This ratio decreases with the increasing epicentral distance and it is much discrete in the near-fault region.Furthermore,site condition also influences this ratio.The curve of vertical to horizontal acceleration response spectrum ratios with periods from 0 to 6 second appears to be saddle-shaped generally.The shapes of vertical and horizontal acceleration response spectrum vary within different period ranges.And vertical acceleration response spectrum looks thin comparing to the horizontal counterpart.Except several stations,the ratio between vertical to horizontal predominant periods is less than 1.0.This ratio increases with the increasing epicentral distance and becomes smooth gradually.The study results can provide a reference for choosing the vertical ground motion input during a time history analysis.
引文
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[15]Kim S J,Holub C J,Elnashai A S.Analytical assessmentof the effect of vertical earthquake motion on RC bridgepiers[J].ASCE Journal of Structural Engineering,2011,137(2):252―260.
[16]Kim S J,Elnashai A S.Characterization of shakingintensity distribution and seismic assessment of RCbuildings for the Kashmir(Pakistan)earthquake ofOctober 2005[J].Engineering Structures,2009,31(12):2998―3015.
[17]Kunnath S K,Erduran E,Chai Y H,et al.Effect ofnear-fault vertical ground motions on seismic response ofhighway overcrossings[J].ASCE Journal of BridgeEngineering,2008,13(3):282―290.
[18]Yilmaz Z.Probabilistic seismic hazard assessment for theeffect of vertical ground motions on seismic response ofhighway bridges[D].Davis:University of California,2008.
[19]Malhotra P K.Smooth spectra of horizontal and verticalground motions[J].Bulletin of the Seismological Societyof America,2006,96(2):506―518.
[2]Yanf J,Lee C M.Characteristics of vertical andhorizontal ground motions recorded during the Niigata-ken Chuetsu,Japan Earthquake of 23 October 2004[J].Engineering Geology,2007,94(1/2):50―64.
[3]贾俊峰,欧进萍.近断层竖向地震动峰值特征[J].地震工程与工程振动,2009,29(1):44―49.Jia Junfeng,Ou Jinping.Peak amplitude characteristics ofvertical seismic ground motions in near-fault regions[J].Earthquake Engineering and Engineering Vibration,2009,29(1):44―49.(in Chinese)
[4]Kim S J,Elnashai A S.Seismic assessment of RCstructures considering vertical ground motion[D].Urbana:University of Illinois at Urbana-Champaign,2008.
[5]贾俊峰,欧进萍.近断层竖向与水平向加速度反应谱比值特征[J].地震学报,2010,32(1):41―50.Jia Junfeng,Ou Jinping.Vertical-to-horizontalacceleration response spectrum ratio of near-fault groundmotion[J].Acta Seismologica Sinica,2010,32(1):41―50.(in Chinese)
[6]李恒,秦小军.竖向与水平向地震动加速度反应谱比特性分析[J].地震工程与工程振动,2010,30(1):8―14.Li Heng,Qin Xiaojun.Study on characteristics of verticalto horizontal acceleration response spectral ratio[J].Earthquake Engineering and Engineering Vibration,2010,30(1):8―14.(in Chinese)
[7]Li Xinle,Dou Huijuan,Zhu Xi.Engineeringcharacteristics of near-fault vertical ground motions andtheir effect on the seismic response of bridges[J].Earthquake Engineering and Engineering Vibration,2007,6(4):345―350.
[8]Bozorgnia Y,Campbell K,Niazi M.Observed spectralcharacteristics of vertical ground motion recorded duringworldwide earthquakes from 1957 to 1995[C]//Proc.12WCEE.Auckland,New Zealand,Paper No.2671,2000.
[9]周锡元,徐平,王国权,等.1999年台湾集集地震近断层竖向与水平反应谱比值的研究[J].地震地质,2006,28(3):325-335.Zhou Xiyuan,Xu Ping,Wang Guoquan,et al.A casestudy on near fault vertical to horizontal response spectralratio from the 1999,Chi-Chi,Taiwan,earthquake[J].Seismology and Geology,2006,28(3):325―335.(inChinese)
[10]谢俊举,温增平,高孟潭,等.2008年汶川地震近断层竖向与水平向地震动特征[J].地球物理学报,2010,53(8):1796―1805.Xie Junju,Wen Zengping,Gao Mengtan,et al.Characteristics of near-fault vertical and horizontalground motion from the Wenchuan earthquake[J].Chinese Journal of Geophysics,2010,53(8):1796―1805.(in Chinese)
[11]Kikuchi M,Dan K,Yashiro K.Seismic behavior of areinforced concrete building due to large vertical groundmotions in near-source regions[C]//Proc.12WCEE.Auckland,New Zealand,Paper No.1876,2000.
[12]Yamazaki S,Minami S,Mimura H,et al.Effects ofvertical ground motions on earthquake response of steelframes[C]//Proc.12WCEE.Auckland,New Zealand,Paper No.0663,2000.
[13]Kim S J,Holub C J,Elnashai A S.Analytical andexperimental investigations of the effect of verticalground on RC bridge piers[C].The 14th WorldConference on Earthquake Engineering.Beijing,China,Paper No.S28-002,2008.
[14]Elnashai A S,Spencer B,Kuchma D,et al.Analysis anddistributed hybrid simulation of shear-sensitive RCbridges subjected to horizontal and vertical earthquakeground motion[J].Technical Memorandum of PublicWorks Research Institute,2005,3983:351―368.
[15]Kim S J,Holub C J,Elnashai A S.Analytical assessmentof the effect of vertical earthquake motion on RC bridgepiers[J].ASCE Journal of Structural Engineering,2011,137(2):252―260.
[16]Kim S J,Elnashai A S.Characterization of shakingintensity distribution and seismic assessment of RCbuildings for the Kashmir(Pakistan)earthquake ofOctober 2005[J].Engineering Structures,2009,31(12):2998―3015.
[17]Kunnath S K,Erduran E,Chai Y H,et al.Effect ofnear-fault vertical ground motions on seismic response ofhighway overcrossings[J].ASCE Journal of BridgeEngineering,2008,13(3):282―290.
[18]Yilmaz Z.Probabilistic seismic hazard assessment for theeffect of vertical ground motions on seismic response ofhighway bridges[D].Davis:University of California,2008.
[19]Malhotra P K.Smooth spectra of horizontal and verticalground motions[J].Bulletin of the Seismological Societyof America,2006,96(2):506―518.
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