基于结构强震记录的结构时变模态参数识别
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摘要
为研究结构在地震过程中动力特性变化和损伤过程,为结构地震损伤评估提供可靠依据,采用递归式在线系统辨识算法RARX模型,利用结构强震记录识别了结构时变模态参数。以一座6层钢筋混凝土框架结构为例,识别了其时变自振频率、阻尼比和等效刚度。结果发现:在小地震动作用下,结构自振频率随时间几乎不发生改变;在大地震动作用的整个时间过程中,结构自振频率随时间逐渐降低,降低到一定程度到达最低点后,频率开始回升,直至地震结束,但最后不能回升到初始值,说明经历大震发生损伤的结构在震后性能会有所恢复;结构等效刚度变化趋势和自振频率相同,但在大震中下降比频率下降大的多;结构阻尼比在经历大震发生损伤后增大。结果可供结构地震损伤预测及结构震后安全鉴定参考。
To study changes of structural dynamic characteristics and structural seismic damage process during earthquakes for the purpose of structural seismic damage assessment,time-varying modal parameters were identified based on the strong motion records by using the on-line system identification method-RARX model.As an example,the natural frequencies,damping ratios and equivalent stiffnesses of a 6-story reinforcement concrete frame structure were identified from its strong motion records during two earthquakes;one is small earthquake,and the other is great earthquake.The results showed that the natural frequencies do not change during small earthquake;in great earthquake,the natural frequencies decrease gradually until they reach the lowest point values,and then increase until the end of the earthquake but they can not be recovered to the initial values,those mean the performance of structures can be recovered to a certain extent after the earthquake;the equivalent stiffnesses are changed with the same trend as natural frequencies,but decrease much greater than that of natural frequencies;however,the structural damping ratios increase after damage under the excitation of great earthquake.The results provided a reference for the damage detection and prognosis.
To study changes of structural dynamic characteristics and structural seismic damage process during earthquakes for the purpose of structural seismic damage assessment,time-varying modal parameters were identified based on the strong motion records by using the on-line system identification method-RARX model.As an example,the natural frequencies,damping ratios and equivalent stiffnesses of a 6-story reinforcement concrete frame structure were identified from its strong motion records during two earthquakes;one is small earthquake,and the other is great earthquake.The results showed that the natural frequencies do not change during small earthquake;in great earthquake,the natural frequencies decrease gradually until they reach the lowest point values,and then increase until the end of the earthquake but they can not be recovered to the initial values,those mean the performance of structures can be recovered to a certain extent after the earthquake;the equivalent stiffnesses are changed with the same trend as natural frequencies,but decrease much greater than that of natural frequencies;however,the structural damping ratios increase after damage under the excitation of great earthquake.The results provided a reference for the damage detection and prognosis.
引文
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[2]Izuru T,Nakamura M.Stiffness-damping simultaneous identi-fication using limited earthquake records[J].Earthquake En-gineering and Structural Dynamics,2000,29(8):1219-1238.
[3]Huang C S,Hung S L,Wen C M,et al.A neural networkapproach for structural identification and diagnosis of a build-ing from seismic response data[J].Earthquake Engineeringand Structural Dynamics,2003,32(2):187-206.
[4]Yiannis H,Costas P,Maria P.Multi-objective framework forstructural model identification[J].Earthquake Engineeringand Structural Dynamics,2005,34(6):665-685.
[5]Gong M S,Xie L L,Ou J P.Modal parameter identificationof structure model using shaking table test data[C].The 14thWorld Conference on Earthquake Engineering,2008,PaperNo.05-01-0400.
[6]Lennart L.System Identification-Theory for the User[M].Upper Saddle River,NJ:PTR Prentice Hall,1999.
[7]朱宏平,翁顺.运用小波分析方法进行结构模态参数识别[J].振动与冲击,2007,26(4):1-5.
[8]王轩,夏江宁,宋汉文.基于多轴振动环境试验的模态参数辨识[J].振动与冲击,2008,27(4):52-55.
[9]公茂盛.基于强震记录的结构模态参数识别与应用研究[D].哈尔滨:中国地震局工程力学研究所,2006.
[10]傅志方,华宏星.模态分析理论与应用[M].上海:上海交通大学出版社,2000.
[11]张贤达.现代信号处理[M].北京:清华大学出版社,2002.
[12]Gong Maosheng.Damage Detection of Reinforced ConcreteStructure Based on Limited Strong Motion Records[D].Japan,Tsukuba:Building Research Institute,2008.
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