基于移动平均分解的近断层地震动弹性反应谱研究
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摘要
抗震设计规范中的设计反应谱是通过对大量的中、远场地震记录统计回归分析的结果,而近场地震记录因观测资料缺乏,导致对近场地震动的频谱特性考虑不够.近断层地震动有一些显著区别于远场地震动的特点,其中之一就是近断层地震动包含高频部分和低频脉冲部分.采用一种移动平均滤波器将近断层地震动分解为低频脉冲部分和高频部分,并采用这个方法分解了一些近断层地震动记录,同时研究了近断层地震动弹性反应谱的特性.结果表明,对于单脉冲记录,采用脉冲部分基本可以代表采用原始记录对结构的响应;对于多脉冲记录,因存在一个或多个次高峰,其脉冲部分不能有效代表原始记录对结构的响应,若仅考虑脉冲部分而忽略高频部分将对短周期结构相当不利.
The design response spectrum in seismic design code is the result of a large number of midfield and far-field seismic records statistical regression analysis.As a result of the lack of observation data,the percent of near-field seismic records is small,which leads to the insufficient consideration of the frequency spectrum characteristic of near field ground motions.Near-fault ground motions have some important characteristic that make them different from far-fault ground motions.High-frequency components and low-frequency pulses of near-fault ground motions are among notable specifications.In this paper,a moving average filtering has been designed to decompose the near-fault ground motions into two components having different frequency contents: low-frequency pulses component and high-frequency component.The method is applied to decompose a few selected near-fault records and the elastic response of structure is examined through their response to the decomposed parts.The results emphasizes that for single pulse record the pulse component can effectively represent the response of the structure under the original records.But for multi-pulse record,owing to the existence of one or more peaks,the pulse component can not effectively represent the structure response under the original records.The sole consideration of the pulse component and ignoring the high frequency component is very bad for short cycle structure.
The design response spectrum in seismic design code is the result of a large number of midfield and far-field seismic records statistical regression analysis.As a result of the lack of observation data,the percent of near-field seismic records is small,which leads to the insufficient consideration of the frequency spectrum characteristic of near field ground motions.Near-fault ground motions have some important characteristic that make them different from far-fault ground motions.High-frequency components and low-frequency pulses of near-fault ground motions are among notable specifications.In this paper,a moving average filtering has been designed to decompose the near-fault ground motions into two components having different frequency contents: low-frequency pulses component and high-frequency component.The method is applied to decompose a few selected near-fault records and the elastic response of structure is examined through their response to the decomposed parts.The results emphasizes that for single pulse record the pulse component can effectively represent the response of the structure under the original records.But for multi-pulse record,owing to the existence of one or more peaks,the pulse component can not effectively represent the structure response under the original records.The sole consideration of the pulse component and ignoring the high frequency component is very bad for short cycle structure.
引文
[1]胡进军.近断层地震动方向性效应及超剪切破裂研究[D].哈尔滨:中国地震局工程力学研究所,2009.
[2]BOLT B A.Earthquakes[M].New York:W.H.Free-man,1993.
[3]MAKRIS N.Rigidity-plasticity-viscosity:can electr-orheological dampers protect base-isolated structuresfrom near-source ground motions[J].Earthquake En-gineering and Structural Dynamics,1997(26):571-591.
[4]AGRAWAL A K,HE W L.A closed-form approxima-tion of near-fault ground motion pulses for flexiblestructures[J].In:Proceedings of the 15th ASCE en-gineering mechanics conference,Columbia University,New York,NY,2002:843-845.
[5]BAKER J W.Quantitative classification of near-faultground motions using wavelet analysis[J].Bulletin ofSeismological Society of America,2007,97(5):1486-1501.
[6]FARID G,HOSSEIN J,GHANNAD M A GHANNAD.Study on elastic response of structures to near-faultground motions through record decomposition[J].SoilDynamics and Earthquake Engineering,2010(30):536-546.
[2]BOLT B A.Earthquakes[M].New York:W.H.Free-man,1993.
[3]MAKRIS N.Rigidity-plasticity-viscosity:can electr-orheological dampers protect base-isolated structuresfrom near-source ground motions[J].Earthquake En-gineering and Structural Dynamics,1997(26):571-591.
[4]AGRAWAL A K,HE W L.A closed-form approxima-tion of near-fault ground motion pulses for flexiblestructures[J].In:Proceedings of the 15th ASCE en-gineering mechanics conference,Columbia University,New York,NY,2002:843-845.
[5]BAKER J W.Quantitative classification of near-faultground motions using wavelet analysis[J].Bulletin ofSeismological Society of America,2007,97(5):1486-1501.
[6]FARID G,HOSSEIN J,GHANNAD M A GHANNAD.Study on elastic response of structures to near-faultground motions through record decomposition[J].SoilDynamics and Earthquake Engineering,2010(30):536-546.
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