深软场地大地震远场地震动反应特性分析
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摘要
采用等效线性方法考虑土的动力非线性特性,利用一维波动模型分析了深软场地的地震反应特性,结果表明,与输入苏州人工地震波时的计算结果相比,大地震远场地震动作用时,深软场地的地表水平向峰值加速度明显增大,规准反应谱的特征周期值显著增大,地表设计地震动的水平地震影响系数值明显增大,且两者的差异随输入地震动峰值加速度的增大而增大;当土层剪切波速的变异性由+10%变化到-10%时,地表水平地震影响系数曲线平台值有降低的趋势,规准反应谱的特征周期略有增大,且-10%的变异性对水平地震影响系数的影响要比+10%的变异性的影响显著;土体动剪切模量比和阻尼比均有变异时对地表设计地震动参数的影响较大,且土的阻尼比由-2δ到+2δ变异时,地表水平向峰值加速度和地震影响系数平台值有减小趋势。
Considering nonlinear dynamic characteristic of soils by equivalent linearization method,ground motion characteristics of deep soft site are analyzed base on a one-dimensional wave motion model of horizontally layered soil.The results show that the horizontal peak ground accelerations have a significant amplification under the far-field motions of great earthquake compared with that inputting Suzhou artificial seismic waves;meanwhile,design characteristic periods of normalized response spectrum as well as horizontal seismic influence coefficients of design ground motion are increased;and these amplifications appear to be more obvious with the growing of bedrock peak ground acceleration.When the variability of shear wave velocity of deep soft site changes from +10% to-10%,the horizontal seismic influence coefficient curves of design ground motion decrease significantly;and the characteristic periods of normalized response spectrum increase slightly.The influence due to the-10% variability of shear wave velocity on horizontal seismic influence coefficients would be more significant than that of the +10% variability.What's more,there would be a larger effect on design ground motion parameters if the variability of soil dynamic shear modulus ratio and damping ratio are both changed;and the variability of damping ratio changes from-2δ to +2δ,the horizontal peak ground accelerations of deep soft site and its seismic influence coefficients have a falling tendency.
Considering nonlinear dynamic characteristic of soils by equivalent linearization method,ground motion characteristics of deep soft site are analyzed base on a one-dimensional wave motion model of horizontally layered soil.The results show that the horizontal peak ground accelerations have a significant amplification under the far-field motions of great earthquake compared with that inputting Suzhou artificial seismic waves;meanwhile,design characteristic periods of normalized response spectrum as well as horizontal seismic influence coefficients of design ground motion are increased;and these amplifications appear to be more obvious with the growing of bedrock peak ground acceleration.When the variability of shear wave velocity of deep soft site changes from +10% to-10%,the horizontal seismic influence coefficient curves of design ground motion decrease significantly;and the characteristic periods of normalized response spectrum increase slightly.The influence due to the-10% variability of shear wave velocity on horizontal seismic influence coefficients would be more significant than that of the +10% variability.What's more,there would be a larger effect on design ground motion parameters if the variability of soil dynamic shear modulus ratio and damping ratio are both changed;and the variability of damping ratio changes from-2δ to +2δ,the horizontal peak ground accelerations of deep soft site and its seismic influence coefficients have a falling tendency.
引文
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[2]尹力峰,王坚,谭明,等.不同场地条件下的土层地震反应对比分析[J].内陆地震,2007,21(4):297-303.YIN Li-feng,WANG Jian,TAN Ming,et al.Contrast analysis of earthquake response in different site conditions[J].Inland Earthquake,2007,21(4):297-303.
[3]RATHJE ELLEN M,KOTTKE ALBERT R,TRENT WHITNEY L.Influence of input motion and site property variabilities on seismic site response analysis[J].Journal of Geotechnical and Geoenvironmental Engineering,2010,136(4):607-619.
[4]楼梦麟,严国香,沈建文,等.上海软土动力参数变异性对土层地震反应的影响[J].岩土力学,2004,25(9):368-372.LOU Meng-lin,YAN Guo-xiang,SHEN Jian-wen,et al.Effect of variability of dynamic parameters of soft soil in Shanghai region on seismic respongse of layered soil[J].Rock and Soil Mechanics,2004,25(9):368-372.
[5]张继周,缪林昌,王华敬.土性参数不确定性描述方法的探讨[J].岩土工程学报,2009,30(12):936-940.ZHANG Ji-zhou,MIAO Lin-chang,WANG Hua-jing.Methods for characterizing variability of soil parameters[J].Chinese Journal of Geotechnical En-gineering,2009,30(12):936-940.
[6]YEH C H,RAHMAN M S.Seismic response variability of soil sites[C]//Proceedings of the 6th ASCE Specialty Conference on Probabilistic Mechanics,and Structural and Geotechnical Reliability.Denver:[s.n].,1992:392-395.
[7]陈国兴,刘雪珠,王炳辉.土动力参数变异性对深软场地地表地震动参数的影响[J].防灾减灾工程学报,2007,27(1):1-10.CHEN Guo-xing,LIU Xue-zhu,WANG Bin-hui.Effect of variability of soil dynamic parameters on ground motion parameters for deep soft sites[J].Journal of Disaster Prevention and Mitigation Engineering,2007,27(1):1-10.
[8]战吉艳,陈国兴,刘建达.苏州城区深软场地土剪切波速与土层深度的经验关系[J].世界地震工程,2009,25(2):11-17.ZHAN Ji-yan,CHEN Guo-xing,LIU Jian-da.Empirical relationship between shear wave velocity and soil depth on deep soft sites in urban area of Suzhou city[J].World Earthquake Engineering,2009,25(2):11-17.
[9]陈国兴,朱定华,何启智.GZZ―1型自振柱试验机研制与性能试验[J].震工程与工程振动,2003,23(1):110-114.CHEN Guo-xing,ZHU Ding-hua,HE Qi-zhi.Development and property test of GZZ―1 free vibration column test system[J].Earthquake Engineering and Earthquake Vibration,2003,23(1):110-114.
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