结构振动台模型模态参数识别新方法研究
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摘要
提出了一种结构振动台模型模态参数识别方法,利用结构模型试验过程中地震反应记录,识别结构模型模态参数。首先判断结构模型在地震动激励下发生的是非时变反应还是时变反应,当结构模型发生非时变反应时,采用整个反应记录数据识别模型参数;当结构模型发生时变反应时,则识别模型进入和退出时变反应的时刻点,将整个记录时程分为3段,采用模型退出时变反应后第三段数据识别参数。该方法可以识别试验中每一次地震动输入之后的结构模态参数,得到整个试验过程中结构模型动力特性变化情况。利用所提方法识别了一座12层钢筋混凝土框架结构模型模态参数,并将识别结果和白噪声输入下模态分析结果进行了对比,验证了方法的实用性、可靠性和准确性。结果发现:结构模型自振频率在整个试验过程中呈阶梯状下降,模型发生破坏后,频率降低,阻尼比增加,传递函数幅值随着输入地震动峰值增加而降低。
The objective of the paper is to present a method for modal parameter identification of structure shaking table test model by using the simulated earthquake response data.An adaptive on-line system identification method,the adaptive forgetting through multiple models,is introduced to investigate whether the time-varying response occurred or not during the process of vibration.If the response is time-invariant,the whole response data such as acceleration timehistory is used to identify the modal parameters by using off-line system identification method of ARX model.Otherwise,the whole response time-history is divided into three segments according to the adaptive system identification result if time-varying response occurs,and the third segment data is used to identify the modal parameters.The modal parameters of structural model after every strong motion input and the changes of dynamic properties during the whole test can be obtained by using the method.The method is applied to the shaking table test data of a 12-story RC-frame structure model to identify the modal parameters,and the results are compared with the modal analysis results identified from response data under the excitation of white-noise input.It is shown that the method is with high availability,reliability and accuracy.Furthermore,the analysis results show that the natural frequency of the structure model decreases in stepladder shape during the whole test process.The structural frequencies decrease but the damping ratios increase after the model is damaged.The amplitudes of the transfer function decrease with the increasing of peak value of the input strong motion data.
The objective of the paper is to present a method for modal parameter identification of structure shaking table test model by using the simulated earthquake response data.An adaptive on-line system identification method,the adaptive forgetting through multiple models,is introduced to investigate whether the time-varying response occurred or not during the process of vibration.If the response is time-invariant,the whole response data such as acceleration timehistory is used to identify the modal parameters by using off-line system identification method of ARX model.Otherwise,the whole response time-history is divided into three segments according to the adaptive system identification result if time-varying response occurs,and the third segment data is used to identify the modal parameters.The modal parameters of structural model after every strong motion input and the changes of dynamic properties during the whole test can be obtained by using the method.The method is applied to the shaking table test data of a 12-story RC-frame structure model to identify the modal parameters,and the results are compared with the modal analysis results identified from response data under the excitation of white-noise input.It is shown that the method is with high availability,reliability and accuracy.Furthermore,the analysis results show that the natural frequency of the structure model decreases in stepladder shape during the whole test process.The structural frequencies decrease but the damping ratios increase after the model is damaged.The amplitudes of the transfer function decrease with the increasing of peak value of the input strong motion data.
引文
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[2]曾国英.三维振动台的正弦扫频分析与模态分析[J].机电工程技术,2006,35(1):30—31.
[3]周云,高向宇,阴毅,等.中海名都高层住宅结构模型模拟地震振动台试验研究[J].地震工程与工程振动,2006,26(1):105—110.
[4]胡彦超,陈章位.实验模态分析中一种改进的傅氏域离散正交多项式[J].振动工程学报,2008,21(1):43—47,2008.
[5]伊廷华,李宏男,王国新.基于小波变换的结构模态参数识别[J].振动工程学报,2006,19(1):51—56.
[6]Huang C S,Hung S L,Wen C M,et al.A neuralnetwork approach for structural identification and di-agnosis of a building from seismic response data[J].Earthquake Engineering and Structural Dynamics,2003,32(2):187—206.
[7]Yiannis H,Costas P,Maria P.Multi-objective frame-work for structural model identification[J].Earth-quake Engineering and Structural Dynamics,2005,34(6):665—685.
[8]Lennart L.System Identification-Theory for the User[M].2nd edition.PTR Prentice Hall,Upper SaddleRiver,N.J.,1999.
[9]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.
[10]Andersson P.Adaptive forgetting in recursive identi-fication through multiple models[J].InternationalJournal of Control,1985,42(11):1 175—1 193.
[11]张贤达.现代信号处理[M].北京:清华大学出版社,2002.
[12]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.
[13]Loh C H,Lin HM.Application of off-line and on-lineidentification techniques to building seismic responsedata[J].Earthquake Engineering and Structural Dy-namics,1996,25:269—290.
[14]吕西林,李培振,陈跃庆.12层钢筋混凝土标准框架振动台模型试验的完整数据[R].同济大学土木工程防灾国家重点实验室振动台试验室研究报告,2004.
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