成层地基自由场地面运动的随机模型
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摘要
地表土层通常具有成层的特点,在地震工程中将覆盖土层简化为力学性质沿竖向成层变化,水平向为各向同性的层状半空间体才会得到更符合实际情况的解答。采用频域分析方法,对多层横观各向同性土层对垂直向上的入射剪切波的反应进行了分析。在此基础上,分析了自由场地面运动的频率响应函数,计算了响应位移的功率谱密度函数,并给出了算例。算例表明,多层土的功率谱密度函数具有多个峰值。采用频域分析方法计算层状土地基在地震作用下的位移和应力响应,避免了时域分析时对波在界面处多次反射和透射的反复追踪,思路清晰,步骤简明。
The ground soils are usually layered,and in earthquake engineering,it is reasonable to assume that the mechanical properties of the ground soils vary with the depth of soil,and are homogeneous in all horizontal layers.The analysis method in frequency domain is adopted to treat the transversely isotropic multi-layered soils,and response of soil layers under the upward shear waves is obtained.Based on the above analysis,the frequency response function of free-field ground motion is established.The power spectrum density function of displacement is calculated.An example is also given to illustrate the variation of the power spectrum density function via frequency,it is shown that the power spectrum density function of multi-layered soil has more peaks.Furthermore,by adopting the frequency domain analysis method,the calculation for stress and displacement responses of the layered foundation under earthquakes will be much more simplified due to avoiding the multiple tracing to the reflections and transmissions of the waves on the soil interface in time domain analysis.
The ground soils are usually layered,and in earthquake engineering,it is reasonable to assume that the mechanical properties of the ground soils vary with the depth of soil,and are homogeneous in all horizontal layers.The analysis method in frequency domain is adopted to treat the transversely isotropic multi-layered soils,and response of soil layers under the upward shear waves is obtained.Based on the above analysis,the frequency response function of free-field ground motion is established.The power spectrum density function of displacement is calculated.An example is also given to illustrate the variation of the power spectrum density function via frequency,it is shown that the power spectrum density function of multi-layered soil has more peaks.Furthermore,by adopting the frequency domain analysis method,the calculation for stress and displacement responses of the layered foundation under earthquakes will be much more simplified due to avoiding the multiple tracing to the reflections and transmissions of the waves on the soil interface in time domain analysis.
引文
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[2]欧进萍,王光远.结构随机振动[M].北京:高等教育出版社,1998.Ou Jinping,Wang Guangyuan.Random Vibration of Structures[M].Beijing:Higher Education Press,1998.
[3]徐建国,王博,陈淮,等.大型渡槽结构非线性地震响应分析[J].世界地震工程,2006,22(4):35-40.Xu Jianguo,Wang Bo,Chen Huai,et al.Non-linear earthquake response analysis of a large-scale aqueduct[J].World Earthquake Engineering,2006,22(4):35-40.
[4]廖振鹏.工程波动理论导论[M].2版.北京:科学出版社,2002.Liao Zhenpeng.Introduction to Wave Motion Theories in Engineering(2nd edition)[M].Beijing:Science Press,2002.
[5]王峻,王兰民.地震荷载作用下黄土地基震陷研究[J].世界地震工程,2007,23(4):44-47.Wang Jun,Wang Lanmin.Study on seimic subsidence of loess ground under simulated-earthauake loads[J].World Earthquake Engineering,2007,23(4):44-47.
[6]王赞芝.地基-基础-贮仓结构相互作用系统动力特性及减震控制研究[D].西安:西安建筑科技大学,2005.Wang Zanzhi.Studies on dynamic properties of subsoil-foundation-silo structrue interaction system and vibration reducing measures of silo strcture[D].Xi’an:Xi’an University of Architecture and Technology,2005.
[7]白德贵,陈国兴,王志华.波浪作用对单柱式桥墩地震反应特性的影响[J].世界地震工程,2008,24(4):82-88.Bai Degui,Chen Guoxing,Wang Zhihua.Dynamic analysis of a single-column pier under ground motion and wave action[J].World EarthquakeEngineering,2008,24(4):82-88.
[8]王赞芝.动力机器地基随机振动研究[J].力学与实践,2005,27(4):18-21.Wang Zanzhi.Study on random vibration of subsoil under dynamic machine[J].Mechanics in Engineering,2005,27(4):18-21.
[9]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关系[J].世界地震工程,2009,25(2):11-17.Zhan Jiyan,Chen Guoxing,Liu Jianda.Empirical relationship between shear wave velocity and soil depth on deep soft sites in urban area ofSuzhou city[J].World Earthquake Engineering,2009,25(2):11-17.
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