场地放大系数的理论解答
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摘要
场地系数是各个国家和地区规范中考虑地震动场地效应的关键指标,决定着各类工程结构设防水准,但国内外规范就此存在显著差别。采用土层–基岩理想场地模型,导出了土层场地与参考基岩场地地震动响应定量关系解析表达。提出了场地放大系数一般规律,并通过数值模拟验证了其可靠性,在此基础上对国内外规范场地系数的合理性进行检验。结果表明:土层场地地震动响应与参考基岩场地相比,在全频域空间恒定表现为放大,场地放大系数随场地变软整体表现出增大趋势,这与美国新规范场地系数取值和规律一致;中国规范中软场地系数取值严重偏于保守,强烈地震动作用下软场地系数小于1的现象不合理,中国规范Ⅳ类场地系数普遍小于Ⅲ类的取值方案有待商榷。
The site coefficient is a key index for considering the seismic site effects in various national and regional standards, which determines the criterion of earthquake-resistant design, but there exist significant differences between domestic and foreign standards. Based on the ideal soil-bedrock site model, an analytical expression for the quantitative relationship between soil site and reference bedrock is derived and examined through numerical simulation. The general rules of site amplification coefficient are put forward, and the reliability of different recommended values are verified. The results indicate that the soil ground motion is always amplified in the whole frequency domain compared to the reference bedrock. The site amplification coefficients show the overall increasing trend with the softening of the site, and are consistent with the suggested values in the new NEHRP provisions of the United States of America. The coefficient of soft site in China is seriously conservative and the value is less than 1.0 under strong vibration, which is clearly unreasonable. It is debatable whether the site coefficient of class site IV should be generally less than that of class site III in China's code.
The site coefficient is a key index for considering the seismic site effects in various national and regional standards, which determines the criterion of earthquake-resistant design, but there exist significant differences between domestic and foreign standards. Based on the ideal soil-bedrock site model, an analytical expression for the quantitative relationship between soil site and reference bedrock is derived and examined through numerical simulation. The general rules of site amplification coefficient are put forward, and the reliability of different recommended values are verified. The results indicate that the soil ground motion is always amplified in the whole frequency domain compared to the reference bedrock. The site amplification coefficients show the overall increasing trend with the softening of the site, and are consistent with the suggested values in the new NEHRP provisions of the United States of America. The coefficient of soft site in China is seriously conservative and the value is less than 1.0 under strong vibration, which is clearly unreasonable. It is debatable whether the site coefficient of class site IV should be generally less than that of class site III in China's code.
引文
[1]SEED H B,ROMO M P,SUN J I,et al.The Mexico earthquake of September 19,1985:relationships between soil conditions and earthquake ground motions[J].Earthquake Spectra,1988,4(4):687-729.
[2]HANKS T C,BRADY A G.The loma prieta earthquake,ground motion,and damage in Oakland,Treasure Island,and San Francisco[J].Bulletin of the Seismological Society of America,1991,81(5):2019-2047.
[3]GAO S,LIU H,DAVIS P M,et al.Localized amplification of seismic waves and correlation with damage due to the Northridge earthquake:evidence for focusing in Santa Monica[J].Bulletin of the Seismological Society of America,1996,86(1B):S209-S230.
[4]KIM B,HASHASH Y M A.Site response analysis using downhole array recordings during the March 2011Tohoku-Oki earthquake and the effect of long-duration ground motions[J].Earthquake Spectra,2013,29(S1):S37-S54.
[5]薄景山,李秀领,刘德东,等.土层结构对反应谱平台值的影响[J].地震工程与工程振动,2003,23(4):29-33.(BOJing-shan,LI Xiu-ling,LIU De-dong,et al.Effects of soil layer construction on platform value of response spectra[J].Earthquake Engineering and Engineering Vibration,2003,23(4):29-33.(in Chinese))
[6]薄景山,李秀领,刘红帅.土层结构对地表加速度峰值的影响[J].地震工程与工程振动,2003,23(3):35-40.(BOJing-shan,LI Xiu-ling,LIU Hong-shuai.Effects of soil layer construction on peak accelerations of ground motions[J].Earthquake Engineering and Engineering Vibration,2003,23(3):35-40.(in Chinese))
[7]DARRAGH R B,SHAKAL A F.The site response of two rock and soil station pairs to strong and weak ground motion[J].Bulletin of the Seismological Society of America,1991,81(5):1885-1899.
[8]AKI K.Local site effects on weak and strong ground motion[J].Tectonophysics,1993,218(1):93-111.
[9]KOKUSHO T,SATO K.Surface-to-base amplification evaluated from KiK-net vertical array strong motion records[J].Soil Dynamics and Earthquake Engineering,2008,28(9):707-716.
[10]郭晓云,薄景山,巴文辉.汶川地震不同场地反应谱平台值统计分析[J].地震工程与工程振动,2012,32(4):54-62.(GUO Xiao-yun,BO Jin-shan,BA Wen-hui.Statistical analysis of peak flat values of response spectra in different site condition based on Wenchuan strong ground motions[J].Earthquake Engineering and Engineering Vibration,2012,32(4):54-62.(in Chinese))
[11]崔昊,丁海平.基于KiK-net强震记录的场地调整系数估计[J].地震工程与工程振动,2016,36(4):147-152.(CUI Hao,DING Hai-ping.Estimation of site coefficient based on KiK-net strong-motion seismograph network[J].Earthquake Engineering and Engineering Dynamics,2016,36(4):147-152.(in Chinese))
[12]HWANG H H M,LIN H,HUO J R.Site coefficients for design of buildings in eastern United States[J].Soil Dynamics and Earthquake Engineering,1997,16(1):29-40.
[13]李小军,彭青.不同类别场地地震动参数的计算分析.地震工程与工程振动,2001,21(1):29-36.(LI Xiao-jun,PENG Qing.Calculation and analysis of earthquake ground motion parameters for different site categories[J].Earthquake Engineering and Engineering Vibration,2001,21(1):29-36.(in Chinese))
[14]吕悦军,彭艳菊,兰景岩,等.场地条件对地震动参数影响的关键问题[J].震灾防御技术,2008,3(2):126-135.(LU Yue-jun,PENG Yan-ju,LAN Jing-yan,et al.Some key problems about site effects on seismic ground motion parameters[J].Technology for Earthquake Disaster Prevention,2008,3(2):126-135.(in Chinese))
[15]李瑞山.新一代土层地震反应分析方法研究[D].哈尔滨:中国地震局工程力学研究所,2016.(LI Rui-shan.Research on a new generation technique for ground seismic response analysis[D].Harbin:Institute of Engineering Mechanics,China Earthquake Administration,2016.(in Chinese))
[16]KAKLAMANOS J,BAISE L G,THOMPSON E M,et al.Comparison of 1D linear,equivalent-linear,and nonlinear site response models at six Ki K-net validation sites[J].Soil Dynamics and Earthquake Engineering,2015,69:207-219.
[17]王亮.基于KiK-net强震台网的土层地震动特性研究[D].哈尔滨:中国地震局工程力学研究所,2014.(WANGLiang.The research of soil layer seismic characteristic based on KiK-net strong-motion network[D].Harbin:Institute of Engineering Mechanics,China Earthquake Administration,2014.(in Chinese))
[18]GRIFFITHS S C,COX B R,RATHJE E M.Challenges associated with site response analyses for soft soils subjected to high-intensity input ground motions[J].Soil Dynamics and Earthquake Engineering,2016,85:1-10.
[19]袁晓铭,李瑞山,孙锐.新一代土层地震反应分析方法[J].土木工程学报,2016,49(10):95-102,122.(YUANXiao-ming,LI Rui-shan,SUN Rui.A new generation method for earthquake response analysis of soil layers[J].China Civil Engineering Journal,2016,49(10):95-102,122.(in Chinese))
[20]李兆焱,袁晓铭,王鸾,等.巨厚场地三种土层地震反应分析程序对比检验[J].地震工程与工程振动,2017,37(4):42-50.(LI Zhao-yan,YUAN Xiao-ming,WANGLuan,et al.Verification of three methods for calculating earthquake response of soil layers in deep sites[J].Earthquake Engineering and Engineering Dynamics,2017,37(4):42-50.(in Chinese))
[21]Building Seismic Safety Council of the National Institute of Building Sciences.NEHRP recommended seismic provisions for new buildings and other structures[S].2015.
[22]SEYHAN E,STEWART J P.Semi-empirical nonlinear site amplification from NGA-West2 data and simulations[J].Earthquake Spectra,2014,30(3):1241-1256.
[23]ASCE/SEI 7-16 American Society of Civil Engineers.Minimum design loads for buildings and other structures[S].2016.
[24]GB 18306-2015中国地震动参数区划图[S].2015.(GB18306-2015 Seismic ground motion parameters zonation map of China[S].2015.(in Chinese))
[25]廖振鹏.工程波动理论导论[M].2版.北京:科学出版社,2002.(LIAO Zhen-peng.Introduction to wave motion theories for engineering[M].2nd ed.Beijing:Science Press,2002.(in Chinese))
[26]罗诚,谢俊举,温增平.熊本MW7.0地震近场地表与井下地震动对比研究[J].地震学报,2018,40(1):108-120.(LUO Cheng,XIE Jun-ju,WEN Zeng-ping.Comparison of near-field surface and borehole ground motion observed during the Kumamoto MW7.0 earthquake[J].Acta Seismologica Sinica,2018,40(1):108-120.(in Chinese))
[2]HANKS T C,BRADY A G.The loma prieta earthquake,ground motion,and damage in Oakland,Treasure Island,and San Francisco[J].Bulletin of the Seismological Society of America,1991,81(5):2019-2047.
[3]GAO S,LIU H,DAVIS P M,et al.Localized amplification of seismic waves and correlation with damage due to the Northridge earthquake:evidence for focusing in Santa Monica[J].Bulletin of the Seismological Society of America,1996,86(1B):S209-S230.
[4]KIM B,HASHASH Y M A.Site response analysis using downhole array recordings during the March 2011Tohoku-Oki earthquake and the effect of long-duration ground motions[J].Earthquake Spectra,2013,29(S1):S37-S54.
[5]薄景山,李秀领,刘德东,等.土层结构对反应谱平台值的影响[J].地震工程与工程振动,2003,23(4):29-33.(BOJing-shan,LI Xiu-ling,LIU De-dong,et al.Effects of soil layer construction on platform value of response spectra[J].Earthquake Engineering and Engineering Vibration,2003,23(4):29-33.(in Chinese))
[6]薄景山,李秀领,刘红帅.土层结构对地表加速度峰值的影响[J].地震工程与工程振动,2003,23(3):35-40.(BOJing-shan,LI Xiu-ling,LIU Hong-shuai.Effects of soil layer construction on peak accelerations of ground motions[J].Earthquake Engineering and Engineering Vibration,2003,23(3):35-40.(in Chinese))
[7]DARRAGH R B,SHAKAL A F.The site response of two rock and soil station pairs to strong and weak ground motion[J].Bulletin of the Seismological Society of America,1991,81(5):1885-1899.
[8]AKI K.Local site effects on weak and strong ground motion[J].Tectonophysics,1993,218(1):93-111.
[9]KOKUSHO T,SATO K.Surface-to-base amplification evaluated from KiK-net vertical array strong motion records[J].Soil Dynamics and Earthquake Engineering,2008,28(9):707-716.
[10]郭晓云,薄景山,巴文辉.汶川地震不同场地反应谱平台值统计分析[J].地震工程与工程振动,2012,32(4):54-62.(GUO Xiao-yun,BO Jin-shan,BA Wen-hui.Statistical analysis of peak flat values of response spectra in different site condition based on Wenchuan strong ground motions[J].Earthquake Engineering and Engineering Vibration,2012,32(4):54-62.(in Chinese))
[11]崔昊,丁海平.基于KiK-net强震记录的场地调整系数估计[J].地震工程与工程振动,2016,36(4):147-152.(CUI Hao,DING Hai-ping.Estimation of site coefficient based on KiK-net strong-motion seismograph network[J].Earthquake Engineering and Engineering Dynamics,2016,36(4):147-152.(in Chinese))
[12]HWANG H H M,LIN H,HUO J R.Site coefficients for design of buildings in eastern United States[J].Soil Dynamics and Earthquake Engineering,1997,16(1):29-40.
[13]李小军,彭青.不同类别场地地震动参数的计算分析.地震工程与工程振动,2001,21(1):29-36.(LI Xiao-jun,PENG Qing.Calculation and analysis of earthquake ground motion parameters for different site categories[J].Earthquake Engineering and Engineering Vibration,2001,21(1):29-36.(in Chinese))
[14]吕悦军,彭艳菊,兰景岩,等.场地条件对地震动参数影响的关键问题[J].震灾防御技术,2008,3(2):126-135.(LU Yue-jun,PENG Yan-ju,LAN Jing-yan,et al.Some key problems about site effects on seismic ground motion parameters[J].Technology for Earthquake Disaster Prevention,2008,3(2):126-135.(in Chinese))
[15]李瑞山.新一代土层地震反应分析方法研究[D].哈尔滨:中国地震局工程力学研究所,2016.(LI Rui-shan.Research on a new generation technique for ground seismic response analysis[D].Harbin:Institute of Engineering Mechanics,China Earthquake Administration,2016.(in Chinese))
[16]KAKLAMANOS J,BAISE L G,THOMPSON E M,et al.Comparison of 1D linear,equivalent-linear,and nonlinear site response models at six Ki K-net validation sites[J].Soil Dynamics and Earthquake Engineering,2015,69:207-219.
[17]王亮.基于KiK-net强震台网的土层地震动特性研究[D].哈尔滨:中国地震局工程力学研究所,2014.(WANGLiang.The research of soil layer seismic characteristic based on KiK-net strong-motion network[D].Harbin:Institute of Engineering Mechanics,China Earthquake Administration,2014.(in Chinese))
[18]GRIFFITHS S C,COX B R,RATHJE E M.Challenges associated with site response analyses for soft soils subjected to high-intensity input ground motions[J].Soil Dynamics and Earthquake Engineering,2016,85:1-10.
[19]袁晓铭,李瑞山,孙锐.新一代土层地震反应分析方法[J].土木工程学报,2016,49(10):95-102,122.(YUANXiao-ming,LI Rui-shan,SUN Rui.A new generation method for earthquake response analysis of soil layers[J].China Civil Engineering Journal,2016,49(10):95-102,122.(in Chinese))
[20]李兆焱,袁晓铭,王鸾,等.巨厚场地三种土层地震反应分析程序对比检验[J].地震工程与工程振动,2017,37(4):42-50.(LI Zhao-yan,YUAN Xiao-ming,WANGLuan,et al.Verification of three methods for calculating earthquake response of soil layers in deep sites[J].Earthquake Engineering and Engineering Dynamics,2017,37(4):42-50.(in Chinese))
[21]Building Seismic Safety Council of the National Institute of Building Sciences.NEHRP recommended seismic provisions for new buildings and other structures[S].2015.
[22]SEYHAN E,STEWART J P.Semi-empirical nonlinear site amplification from NGA-West2 data and simulations[J].Earthquake Spectra,2014,30(3):1241-1256.
[23]ASCE/SEI 7-16 American Society of Civil Engineers.Minimum design loads for buildings and other structures[S].2016.
[24]GB 18306-2015中国地震动参数区划图[S].2015.(GB18306-2015 Seismic ground motion parameters zonation map of China[S].2015.(in Chinese))
[25]廖振鹏.工程波动理论导论[M].2版.北京:科学出版社,2002.(LIAO Zhen-peng.Introduction to wave motion theories for engineering[M].2nd ed.Beijing:Science Press,2002.(in Chinese))
[26]罗诚,谢俊举,温增平.熊本MW7.0地震近场地表与井下地震动对比研究[J].地震学报,2018,40(1):108-120.(LUO Cheng,XIE Jun-ju,WEN Zeng-ping.Comparison of near-field surface and borehole ground motion observed during the Kumamoto MW7.0 earthquake[J].Acta Seismologica Sinica,2018,40(1):108-120.(in Chinese))