地震动非平稳特性对结构非线性响应影响的分析
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摘要
虽然地震动的非平稳特性被越来越多的研究者所认识,但是其对结构非线性响应的影响却一直没有较为深入的研究。传统的反应谱和功率谱缺乏对地震动时间信息的表达,而由小波变换得到的地震动局部谱(时变谱)能更准确地反应地震动的非平稳性。更为重要的是,小波变换可以将地震动能量在时间上的分布进行调整而不改变能量在频率上的分布,对考察地震动非平稳性对结构非线性响应的影响非常有利。利用小波变换的上述优势,对比分析了三条实际地震动记录对一榀钢筋混凝土框架非线性时程响应的影响,通过调整其中一条记录的能量在时间上的分布,清楚地表明地震动能量在时间上的集中对结构响应非常不利,并由此提出了有效峰值的概念来定量反应这种表现为能量集中的地震动非平稳性。
The nonstationary characteristic of earthquake ground motion has been clearly understood, however, its effect on the structural nonlinear responses has not been studied comprehensively. The traditional response spectrum and power spectrum do not have the time information of earthquake ground motion, whereas the local spectra (time dependant spectra) by wavelet transform can reflect the nonstationary characteristic more precisely. Especially, wavelet transform has the ability of redistributing the energy of earthquake ground motion in the time domain without any changes in frequency, which is advantageous to the analysis of the effect of nonstationary characteristic on structural responses. A comparison of the effects of three earthquake records, and two altered versions of one of the records with the energy being redistributed by wavelet transform, is carried out. Based on the comparison, the authors point out that the ernergy concentration of earthquake ground motion in the time domain, which is also one kind of nonstationary characteristic, is especially harmful to a structure. Consequently a notion of effective peak is proposed to quantitatively represent the energy concentration.
The nonstationary characteristic of earthquake ground motion has been clearly understood, however, its effect on the structural nonlinear responses has not been studied comprehensively. The traditional response spectrum and power spectrum do not have the time information of earthquake ground motion, whereas the local spectra (time dependant spectra) by wavelet transform can reflect the nonstationary characteristic more precisely. Especially, wavelet transform has the ability of redistributing the energy of earthquake ground motion in the time domain without any changes in frequency, which is advantageous to the analysis of the effect of nonstationary characteristic on structural responses. A comparison of the effects of three earthquake records, and two altered versions of one of the records with the energy being redistributed by wavelet transform, is carried out. Based on the comparison, the authors point out that the ernergy concentration of earthquake ground motion in the time domain, which is also one kind of nonstationary characteristic, is especially harmful to a structure. Consequently a notion of effective peak is proposed to quantitatively represent the energy concentration.
引文
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[11]曹晖,赖明,白绍良.适合于地震工程信号分析的快速小波变换法[J].工程力学,2002,19(4):141~148.Cao Hui,Lai Ming,Bai Shaoliang.Fast algorithm for wavelet transform adaptive to the analysis of signals in earthquake engineering[J].Engineering Mechanics,2002,19(4):141~148.(in Chinese)
[2]Lin Y K,Yong Y.Evolutionary kanai-tajimi earthquake models[J].J.EM,ASCE,1987,113:1119~1137.
[3]Yeh C-H,Wen Y K.Modeling of nonstationary ground motion and analysis of inelastic structural response[J].Structural Safety,1990,8:281~298.
[4]Conte J P,Peng B F.Fully nonstationary analytical earthquake ground-motion model[J].J.EM,ASCE,1997,123(1):15~24.
[5]Basu B,Gupta V K.Non-stationary seismic response of MDOF systems by wavelet transform[J].EESD,1997,26:1243~1258.
[6]Conte J P.Effects of earthquake frequency nonstationary on inelastic structural response[J].Proc.of the10th WCEE,Madrid,Spain,1992,7:3645~3651.
[7]Wang J J.Simulation of non-stationary frequency content and its importance to seismic assessment of structures[J].EESD,2002,31:993~1005.
[8]杨红,曹晖,白绍良.地震波局部时频特性对结构非线性响应的影响[J].土木工程学报,2001,34(4):78~82.Yang Hong,Cao Hui,Bai Shaoliang.Effects of local time-frequency characteristics of earthquake waves on structural nonlinear responses[J].China Civil Engineering Journal,2001,34(4):78~82.(in Chinese)
[9]曹晖,赖明,白绍良.地震地面运动局部谱密度的小波变换估计[J].工程力学,2004,21(5):109~115.Cao Hui,Lai Ming,Bai Shaoliang.Estimation of local spectral density of earthquake ground motion based on wavelet transform[J].Engineering Mechanics,2004,21(5):109~115.(in Chinese)
[10]Cao Hui,Yang Hong,Michael I Friswell,Bai Shaoliang.The analysis of earthquake waves based on nonlinear responses of RC structures[C].Proc.of7th Biennial ASME Conference on Engineering Systems Design and Analysis,2004,Manchester,No.58253.
[11]曹晖,赖明,白绍良.适合于地震工程信号分析的快速小波变换法[J].工程力学,2002,19(4):141~148.Cao Hui,Lai Ming,Bai Shaoliang.Fast algorithm for wavelet transform adaptive to the analysis of signals in earthquake engineering[J].Engineering Mechanics,2002,19(4):141~148.(in Chinese)
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