苏通桥对非一致地震地面运动的反应和人工波质量的讨论
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摘要
台湾集集地震SMART-II密集台阵的,带有GPS国际标准时间校准的7群非一致地震地面加速度记录,和2群以杂交法针对苏通桥桥位断层和地质构造产生的非一致地震人工地面加速度时程历史作为输入,分析了世界最大跨斜拉桥——苏通桥——对非一致地震地面运动的变形和内力反应。每群地震输入由两个或三个台站的三分量加速度记录组成。还考虑顺桥向与波传播方向、断层走向间不同夹角、大桥是否跨越断层的情况下非一致地震地面运动的反应,并与由每群台站记录中含最大水平地面峰值加速度的记录构成的一致地震地面运动的反应做了比较。比较表明:尽管相应的一致地震输入是由一群台站记录中含最大水平地面峰值加速度的记录组成,苏通桥的半数非一致地震反应仍比相应的一致地震反应大,个别情况的非一致反应甚至比一致反应大得多。因此,苏通桥这样的特大桥的抗震设计应当考虑非一致地震的影响。还提出桥梁设计者应根据桥的动力特性对地震安全性评价提出所需的地震动参数。还检查了有关部门对苏通桥抗震设计提供的人工加速度波的反应谱和互相关系数,结果表明桥梁设计者应当在多方面检查所提供的人工波的质量。
7 groups of asynchronous ground acceleration time histories of Chichi earthquake,Taiwan,Sept.21,1999,recorded by a dense closely spaced array SMART-II with GPS international standard time calibration,and 2 groups of synthetic asynchronous acceleration time histories generated by using a hybrid method of mode superposition and finite difference are used as earthquake ground motion inputs,to analyze earthquake responses of Sutong cable-stayed bridge with the longest span in the world.Different angles between the longitudinaldirection of the bridge and wave traveling direction or direction of Chelonpu fault,and cases of fault-crossing or fault-no-crossing of the bridge are considered.The responses are compared with those to related synchronous seismic ground motions consisting of those with the largest peak ground acceleration in each group of inputs.The results show that responses of such a long-span bridge to asynchronous seismic ground motions are very likely to be larger and sometime much larger than those to related synchronous seismic ground motions.Therefore,seismic design of such long-span bridges should consider effects of asynchronous seismic ground motions.The paper also evaluates quality of synthetic ground motion time histories given by a concerned institute with respect to response spectra and cross-correlation coefficients between synthetic time histories.The results show that bridge designers must check quality of the synthetic time histories.
7 groups of asynchronous ground acceleration time histories of Chichi earthquake,Taiwan,Sept.21,1999,recorded by a dense closely spaced array SMART-II with GPS international standard time calibration,and 2 groups of synthetic asynchronous acceleration time histories generated by using a hybrid method of mode superposition and finite difference are used as earthquake ground motion inputs,to analyze earthquake responses of Sutong cable-stayed bridge with the longest span in the world.Different angles between the longitudinaldirection of the bridge and wave traveling direction or direction of Chelonpu fault,and cases of fault-crossing or fault-no-crossing of the bridge are considered.The responses are compared with those to related synchronous seismic ground motions consisting of those with the largest peak ground acceleration in each group of inputs.The results show that responses of such a long-span bridge to asynchronous seismic ground motions are very likely to be larger and sometime much larger than those to related synchronous seismic ground motions.Therefore,seismic design of such long-span bridges should consider effects of asynchronous seismic ground motions.The paper also evaluates quality of synthetic ground motion time histories given by a concerned institute with respect to response spectra and cross-correlation coefficients between synthetic time histories.The results show that bridge designers must check quality of the synthetic time histories.
引文
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[3]Ketchum M A,Charles S.Golden Gate Bridge seismic evaluation[R].Report of Lin T Y International,Imbsen&Associates,Inc.and Geospectra,Inc.Lin T Y International,San Francisco,USA.1990.
[4]Panza G F,Alvarez L,Aoudia A,Ayadi A,Benhallou H,Benouar D,Bus Z,Chen Y T,Cioflan C,Ding Z F.Realistic modeling of seismic input for megacities and large urban areas[R].The UNESCO/IUGS/IGCP Project414,Episodes,2002,25(3):160～184.
[5]中国地震局.工程场地地震安全性评价技术规范GB17741-1999[S].北京,中国地震出版社,1999.China Institute of Seismological Engineering.Code of seismic safety evaluation of engineering sites GB17741-1999[S].Beijing:China Seismology Press,1999.(in Chinese)
[6]The Caltrans Seismic Advisory Board.Guidline for generation of response-spactrum-compatible Roch motion time histories for application to Caltrans toll bridge seismic retrofit projects[S].Caltrans,1996.
[7]AASHTO.LRFD bridge design specifications[S].2nd Edition with Revisions up to2002,AASHTO.
[8]EUROCODE8.Design provisions for earthquake resistance of structures[S].Part2:Bridges,CEN,1996.
[9]Lin T Y.International/Moffatt&Nichol Engineers.San Francisco-Oakland Bay Bridge,east span seismic safety project design criteria[S].Draft99,Revision7,1999.
[10]李焯芬.香港青马大桥地震危险性分析(青马大桥地震危险性评估最终报告)[R].香港大学土木及结构工程系和广东省地震局研究报告,1997.Li Zhaofen.Seismic analysis of Tsing Ma suspension bridge(final version)[R].Report of Hong Kong University&Guangdong Institute of Seismological Engineering,1997.(in Chinese)
[11]中国交通部标准.公路工程抗震设计规范JTJ004-89[S].北京:交通出版社,1990.China Ministry of Communication.Specifications for seismic design of highway engineering JTJ004-89[S].Beijing:China Jiaotong Press,1990.(in Chinese)
[12]江苏省地震工程研究院.苏通桥工程场地地震安全性评价报告[R],2000.Jiangsu Institute of Seismological Engineering.Seismic safety evaluation report of engineering site of Sutong Bridge[R].2000.(in Chinese)
[13]秦权,楼磊.非经典阻尼对悬索桥地震反应的影响[J].土木工程学报,1999,32(3):17～22.Qin Quan,Lou Lei.Effects of non-proportional damping on seismic responses of long span bridges[J].China Civil Engineering Journal,1999,32(3):17～22.(in Chinese)
[14]江苏省地震工程研究院.苏通长江公路大桥初步设计基础资料汇报材料:桥位地震与地震参数研究[R],2002.Investigations on seismology and seismic parameters of bride location,report on basic documents for preliminary design of Sutong Yanzi River Bridge[R].Jiangsu Institute of Seismological Engineering,2002.(in Chinese)
[15]贺瑞,秦权.产生时程分析用的高质量地面运动时程的新方法[J].工程力学,2006,23(8):12～18.He Rui.Qin Quan.New methods for generating high quality acceleration time histories[J].Engineering Mechanics,2006,23(8):12～18.(in Chinese)
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