隔震高层结构的悬臂梁模型的地震反应研究
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摘要
对底部隔震悬臂梁的地震等效作用和效应进行了研究。水平力作用下具有弯曲型侧移曲线的悬臂梁在动力特征上与高层结构接近,隔震悬臂梁可作为隔震高层结构的一种等效的简化模型。采用伯努利-欧拉梁理论推导出底部隔震悬臂梁的周期和振型,利用振型反应分解谱法分析隔震悬臂梁的地震效应,研究隔震前后各振型的等效地震作用的变化。研究发现隔震高层减振的主要原因在于调整了各振型对内力的贡献比例,延长了高阶振型的周期,从而降低高阶振型的影响,实现减振的目的;隔震对结构上部和底部作用也不同,且对剪力影响大于弯矩;隔震层刚度越弱,对高阶振型的抑制作用越明显,隔震后与隔震前1阶振型的周期比大于1.4可取得较好的隔震效果,规则的隔震高层结构可只采用2个振型计算。
Earthquake actions and seismic effects are studied for base-isolated cantilever beam.Based on the assumption that the dynamic characteristics of cantilever beams,with bending deformation curve of lateral displacement when subjected to lateral forces,are similar to those of high-rise structures,the base-isolated cantilever beam is investigated in this study as an equivalent simplified model of high-rise structures.Vibration periods and modes are derived from the Bernoulli-Euler theory,and earthquake responses are calculated with the mode decomposition response spectrum method.The seismic modal effects of pre-and post-isolation are then examined.It is found that seismic-effect adjustment of each mode is the main mechanism of seismic reduction of isolated high-rise structures and that the higher modes contribution is reduced with periods of the higher modes elongated.Other findings include that base-isolation influence on the substructure is different from the upper-structure,that earthquake-response variation of shear is more significant than that of the moment,and that the reduction of the higher modes is more significant with lower isolation stiffness.It is suggested that the fundamental period ratio of the post-and pre-isolation be over 1.4,and that seismic effect of base-isolated regular high-rise structure can be calculated with two lowest modes alone.
Earthquake actions and seismic effects are studied for base-isolated cantilever beam.Based on the assumption that the dynamic characteristics of cantilever beams,with bending deformation curve of lateral displacement when subjected to lateral forces,are similar to those of high-rise structures,the base-isolated cantilever beam is investigated in this study as an equivalent simplified model of high-rise structures.Vibration periods and modes are derived from the Bernoulli-Euler theory,and earthquake responses are calculated with the mode decomposition response spectrum method.The seismic modal effects of pre-and post-isolation are then examined.It is found that seismic-effect adjustment of each mode is the main mechanism of seismic reduction of isolated high-rise structures and that the higher modes contribution is reduced with periods of the higher modes elongated.Other findings include that base-isolation influence on the substructure is different from the upper-structure,that earthquake-response variation of shear is more significant than that of the moment,and that the reduction of the higher modes is more significant with lower isolation stiffness.It is suggested that the fundamental period ratio of the post-and pre-isolation be over 1.4,and that seismic effect of base-isolated regular high-rise structure can be calculated with two lowest modes alone.
引文
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[14]Craig R R Jr.结构动力学[M].北京:人民交通出版社,1996.Craig R R Jr.Structural dynamics[M].Beijing:ChinaCommunications Press,1996.(in Chinese)
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[3]Taisei Co.Reducing vibrations caused by earthquakesand strong winds,Hybrid TASS Method[EB].http://www.taisei.co.jp/english/technology/3a_comfort.html,2010.
[4]苏键,温留汉.黑沙,周福霖.高层隔震建筑性能分析[J].建筑结构,2009,39(11):40―42.Su Jian,Wenliuhan.Heisha,Zhou Fulin.Study ondynamic characteristics of base isolated high-risebuilding[J].Building Structure,2009,39(11):40―42.(in Chinese)
[5]Kelly J M.Earthquake resistant design with rubber[M].2nd ed.London:Springer Verlag London Limited,1997.
[6]李中锡,周锡元.规则型隔震房屋的自振特性和地震反应分析方法[J].地震工程与工程震动,2002,22(2):33―41.Li Zhongxi,Zhou Xiyuan.Vibration property andearthquake response analysis method for regular isolatedbuilding[J].Earthquake Engineering and EngineeringVibration,2002,22(2):33―41.(in Chinese)
[7]刘文光,杨巧荣,周福霖.大高宽比隔震结构地震反应的实用分析方法[J].地震工程与工程振动,2004,24(4):115―121.Liu Wenguang,Yang Qiaorong,Zhou Fulin.Simplifiedmethod of earthquake response analysis for slenderisolated structure[J].Earthquake Engineering andEngineering Vibration,2004,24(4):115―121.(inChinese)
[8]付伟庆,刘文光,王建,王焕定.高层隔震结构的等效简化模型研究[J].地震工程与工程振动,2005,25(6):141―145.Fu Weiqing,Liu Wenguang,Wang Jian,Wang Huanding.Research on practical design method of regularhigh-rising isolated structure[J].Earthquake Engineeringand Engineering Vibration,2005,25(6):141―145.(inChinese)
[9]王焕定,付伟庆,刘文光,于德湖,程树良.规则隔震结构等效简化模型的研究[J].工程力学,2006,23(8):138―143.Wang Huanding,Fu Weiqing,Liu Wenguang,Yu Dehu,Cheng Shuliang.Research on equivalent simplifiedmodel of regular shock-insulation building[J].Engineering Mechanics,2006,23(8):138―143.(inChinese)
[10]Ariga T,Kanno Y,Takewaki I.Resonant behaviour ofbase-isolated high-rise buildings under long-periodground motions[J].Structural Design of Tall and SpecialBuildings,2006,15:325―338.
[11]Li Q S,Cao H,Li G.Analysis of free vibrations of tallbuildings[J].Journal of Engineering Mechanics,ASCE,1994,120(9):1861―1876.
[12]Li Q S,Fang J Q,Jeary A P.Free vibration analysis ofcantilevered tall structures under various axial loads[J].Journal of Engineering Structures,ASCE,2000,22(5):525―534.
[13]Takewaki I.Robustness of base-isolated high-risebuildings under code-specified ground motions[J].Structural Design of Tall and Special Buildings,2008,17(2):257―271.
[14]Craig R R Jr.结构动力学[M].北京:人民交通出版社,1996.Craig R R Jr.Structural dynamics[M].Beijing:ChinaCommunications Press,1996.(in Chinese)
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