高墩梁桥考虑墩身高阶振动的水平向主导振型
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摘要
规则中、低墩梁桥的水平向动力特性主要取决于对应方向的基本振型,因而可近似按单自由度体系对其进行抗震性能研究和抗震设计。而高墩梁桥由于墩身质量参与和高阶振型影响,其动力特性较为复杂,难以借用单自由度体系模型进行抗震分析和研究。为进一步了解高墩梁桥的动力特性和地震反应特点,将高墩梁桥简化成单墩-质点体系模型,考虑墩身质量参与和高阶振型,分别研究墩高、墩顶集中质量和梁-墩质量比等参数对体系水平向主导振型分布的影响,提出梁-墩质量比是决定单墩-质点体系水平向振型质量参与系数的主要因素,并通过曲线拟合给出了二者间的函数关系式;再利用反应谱方法计算体系在不同地震动输入下的墩底内力和墩顶位移,分离出前几阶水平向振型对体系地震反应的贡献率,依此给出因计算目标而异的选取单墩-质点体系水平向主导振型的合理判据。
In the case of high-pier beam bridges, different from the regular mediun-length-pier or short-pier beam bridges, due to the participation of pier column mass and influence of higher vibration modes in horizontal directions, the dynamically complex structure under seismic attack could not be effectively analyzed based on SDOF model any longer. To make a step further to understand the dynamic properties and seismic responses of high-pier beam bridges, a single-col-umn-and-mass (SCM) system as the simplified dynamic model for high-pier beam bridges is employed in consideration of the pier shaft mass participation as well as the higher vibration modes, to study the influences of system parameters including pier height, pier-top concentrative mass and beam to pier mass ratio on the distribution of horizontal predominant vibration modes. It shows that the beam to pier mass ratio is the dominant factors deciding the horizontal modal mass partici-pating coefficients of the SCM system and then the definite relations between them are formulated. The response spectrum method is applied to compute the pier-bottom seismic force and pier-top displacement of the SCM system under inputs from several different ground motion records. The significant modal contributions to system seismic responses are identified to form reasonable criteria for selection of the SCM system's horizontal predominant vibration modes according to diverse evaluation objectives.
In the case of high-pier beam bridges, different from the regular mediun-length-pier or short-pier beam bridges, due to the participation of pier column mass and influence of higher vibration modes in horizontal directions, the dynamically complex structure under seismic attack could not be effectively analyzed based on SDOF model any longer. To make a step further to understand the dynamic properties and seismic responses of high-pier beam bridges, a single-col-umn-and-mass (SCM) system as the simplified dynamic model for high-pier beam bridges is employed in consideration of the pier shaft mass participation as well as the higher vibration modes, to study the influences of system parameters including pier height, pier-top concentrative mass and beam to pier mass ratio on the distribution of horizontal predominant vibration modes. It shows that the beam to pier mass ratio is the dominant factors deciding the horizontal modal mass partici-pating coefficients of the SCM system and then the definite relations between them are formulated. The response spectrum method is applied to compute the pier-bottom seismic force and pier-top displacement of the SCM system under inputs from several different ground motion records. The significant modal contributions to system seismic responses are identified to form reasonable criteria for selection of the SCM system's horizontal predominant vibration modes according to diverse evaluation objectives.
引文
[1]Caltrans.Seismic Design Criteria[S].Version 3.1,Feb.2004,U.S.A.
[2]中华人民共和国交通部部标准.公路工程抗震设计规范(JTJ 004-89)[S].第1版,北京:人民交通出版社,1989,11.
[3]Anil K.Chopra,Rakesh K.Goel.AModal Pushover AnalysisProcedure to Estimate Seismic Demands for Buildings:Theoryand Preliminary Evaluation[R].PEER Report 2001/03,Pa-cific Earthquake Engineering Research Center,College of En-gineering,University of California Berkeley,January 2001.
[4]Chopra AK,Goel RK.A modal pushover analysis procedurefor estimating seismic demands for buildings[J].EarthquakeEngineering and Structural Dynamics,2002;31(3):561—582.
[5]Tatjana Isakovic and Matej Fischinger.Higher modes in sim-plified inelastic seismic analysis of single column bent viaducts[J].Earthquake Engineering and Structural Dynamics,2006;35:95—114.
[6]T.S.Paraskeva1,A.J.Kappos1 and A.G.Sextos.Exten-sion of modal pushover analysis to seismic assessment of bridg-es[J].Earthquake Engineering and Structural Dynamics,2006;35:1269—1293.
[7]李建中,宋晓东,范立础.桥梁高墩位移延性能力的探讨[J].地震工程与工程振动,2005,25(1):43—48.
[8]施洲,赵人达.桥梁结构边界条件变异对固有振动特性的影响分析[J].振动与冲击,2007,26(2):141—145.
[2]中华人民共和国交通部部标准.公路工程抗震设计规范(JTJ 004-89)[S].第1版,北京:人民交通出版社,1989,11.
[3]Anil K.Chopra,Rakesh K.Goel.AModal Pushover AnalysisProcedure to Estimate Seismic Demands for Buildings:Theoryand Preliminary Evaluation[R].PEER Report 2001/03,Pa-cific Earthquake Engineering Research Center,College of En-gineering,University of California Berkeley,January 2001.
[4]Chopra AK,Goel RK.A modal pushover analysis procedurefor estimating seismic demands for buildings[J].EarthquakeEngineering and Structural Dynamics,2002;31(3):561—582.
[5]Tatjana Isakovic and Matej Fischinger.Higher modes in sim-plified inelastic seismic analysis of single column bent viaducts[J].Earthquake Engineering and Structural Dynamics,2006;35:95—114.
[6]T.S.Paraskeva1,A.J.Kappos1 and A.G.Sextos.Exten-sion of modal pushover analysis to seismic assessment of bridg-es[J].Earthquake Engineering and Structural Dynamics,2006;35:1269—1293.
[7]李建中,宋晓东,范立础.桥梁高墩位移延性能力的探讨[J].地震工程与工程振动,2005,25(1):43—48.
[8]施洲,赵人达.桥梁结构边界条件变异对固有振动特性的影响分析[J].振动与冲击,2007,26(2):141—145.
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