深覆盖土层Rayleigh阻尼矩阵建模问题的讨论
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摘要
分别应用时域和频域分析方法对土层的地震反应进行了计算,通过比较时域和频域的计算结果,探讨了深覆盖土层地震反应时域分析中Rayleigh阻尼矩阵合理建模的重要性。数值结果表明:在深覆盖土层地震反应时域分析中,Rayleigh比例阻尼矩阵不同建模方式对土层加速度反应计算结果的准确性影响很大,而对土层位移反应计算结果的准确性影响非常有限。建议当土层基频高于基岩地震波的主要分量激励频率时,确定Rayleigh阻尼矩阵比例系数的第2个自振频率ωn可选取土层第2或第3阶低阶自振频率,而当土层基频接近于、低于特别是远低于基岩地震波的主要分量激励频率时,应重视土层高阶振型共振效应对土层地震反应的贡献,此时ωn应选取为输入基岩地震波反应谱的峰值频率ωR。
The seismic response of soil layers is calculated by using the methods of time domain and frequency domain separately.Through the comparison of the calculated results between the time domain and the frequency domain,the importance of reasonable modeling by Rayleigh damping matrix in time domain analysis of earthquake response of soil layers with deep deposit is discussed.The numerical results show that in the time domain analysis of earthquake response of soil layers with deep deposit,different modeling methods of Rayleigh proportional damping matrix have great influence on the accuracy of the results of the acceleration response of soils but a very limited impact on that of the displacement response of soils.It is suggested that when the fundamental frequency of soil layers is higher than the excitation frequency of the main component of the bedrock seismic waves,the low-order natural frequency such as the second or third should be selected as the second natural frequency to determine the Rayleigh damping matrix proportion coefficient.When the fundamental frequency of the soil layer is close to and especially much lower than the excitation frequency of the main component of the bedrock seismic waves,the contribution of high-order modes resonance effect on the seismic response of soil layers should be highlighted and ω n should be selected as the response spectrum peak frequency ω R of the input bedrock seismic waves.
The seismic response of soil layers is calculated by using the methods of time domain and frequency domain separately.Through the comparison of the calculated results between the time domain and the frequency domain,the importance of reasonable modeling by Rayleigh damping matrix in time domain analysis of earthquake response of soil layers with deep deposit is discussed.The numerical results show that in the time domain analysis of earthquake response of soil layers with deep deposit,different modeling methods of Rayleigh proportional damping matrix have great influence on the accuracy of the results of the acceleration response of soils but a very limited impact on that of the displacement response of soils.It is suggested that when the fundamental frequency of soil layers is higher than the excitation frequency of the main component of the bedrock seismic waves,the low-order natural frequency such as the second or third should be selected as the second natural frequency to determine the Rayleigh damping matrix proportion coefficient.When the fundamental frequency of the soil layer is close to and especially much lower than the excitation frequency of the main component of the bedrock seismic waves,the contribution of high-order modes resonance effect on the seismic response of soil layers should be highlighted and ω n should be selected as the response spectrum peak frequency ω R of the input bedrock seismic waves.
引文
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[2]廖振鹏.近场波动问题的有限元解法[J].地震工程与工程振动,1984,4(2):1–14.(LIAO Zhen-peng.A finite element method for near-field wave motion in heterogeneous materials[J].Earthquake Engineering and Engineering Vibration,1984,4(2):1–14.(in Chinese))
[3]楼梦麟,张静.结构爆破地震反应计算中的阻尼模型[J].防护工程,2009,31(1):15–19.(LOU Meng-lin,ZHANG Jing.Damping models in calculation of the structure blasting seismic response[J].Protective Engineering,2009,31(1):15–19.(in Chinese))
[4]楼梦麟,殷琳.关于高土坝地震反应分析中阻尼模型的讨论[J].水力发电学报,2009,28(5):103–107.(LOU Meng-lin,YIN Lin.Discussion on damping models for seismic response analysis of high earth dams[J].Journal of Hydroelectric Engineering,2009,28(5):103–107.(in Chinese))
[5]楼梦麟,张静.大跨度拱桥地震反应分析中阻尼模型的讨论[J].振动与冲击,2009,28(5):22–26.(LOU Meng-lin,ZHANG Jing.Discussion on damping models for seismic response analysis of long-span bridge[J].Journal of Vibration and Shock,2009,28(5):22–26.(in Chinese))
[6]GB17741—2005工程场地地震安全性评价[S].北京:中国标准出版社,2005.(GB17741—2005Evaluation of seismic for engineering sites[S].Beijing:Standards Press of China,2005.(in Chinese))
[7]楼梦麟,潘旦光.滞后阻尼在土层时域分析中的应用[J].同济大学学报(自然科学版),2004,32(3):281–285.(LOU Meng-lin,PAN Dan-guang.Hysteretic damping application in time domain analysis of soil layer[J].Journal of Tongji University(National Science),2004,32(3):281–285.(in Chinese))
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