强震输入方式与地基模型对重力坝反应的影响
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摘要
采用无质量地基模型和弹簧–阻尼边界模型研究了在不同频谱地震荷载、不同基岩与混凝土弹性模量比值条件下重力坝的地震反应。基于大量计算分析,提出等效结构阻尼的理念与近似方法,使无质量地基模型计算坝体反应与考虑辐射阻尼效应的结果相接近。结果表明:弹簧–阻尼边界对重力坝的影响与不考虑辐射阻尼的无质量地基相比,位移和应力反应减小,降幅范围为10%～65%;随着基岩与混凝土弹性模量比值的增加,降幅总体减小。采用等效结构阻尼无质量地基模型的重力坝反应与使用弹簧–阻尼边界以计入辐射阻尼效应的结果接近,位移误差在7%以内。
Different earthquake input models, i.e. massless foundation and viscous-spring boundary models, are employed to analyze the seismic response of gravity dams. The effects of different spectral earthquakes, different ratios of modulus of foundation rock to dam concrete and different dam heights are taken into account. A concept of increased equivalent structural damping used in massless foundation model for approximately considering the effects of radiation damping is presented based on case studies. The results demonstrate that the crest displacements and the maximum tensile stresses in dams are reduced using the viscous-spring boundary model compared with those obtained by the massless foundation model. The reduction amplitude of the response ranges between 10% and 65%, and it decreases with the increasing modulus of foundation rock. It is concluded that the structural response using the massless foundation model with increased equivalent structural damping is close to that obtained from the viscous-spring boundary model with an error of 7%.
Different earthquake input models, i.e. massless foundation and viscous-spring boundary models, are employed to analyze the seismic response of gravity dams. The effects of different spectral earthquakes, different ratios of modulus of foundation rock to dam concrete and different dam heights are taken into account. A concept of increased equivalent structural damping used in massless foundation model for approximately considering the effects of radiation damping is presented based on case studies. The results demonstrate that the crest displacements and the maximum tensile stresses in dams are reduced using the viscous-spring boundary model compared with those obtained by the massless foundation model. The reduction amplitude of the response ranges between 10% and 65%, and it decreases with the increasing modulus of foundation rock. It is concluded that the structural response using the massless foundation model with increased equivalent structural damping is close to that obtained from the viscous-spring boundary model with an error of 7%.
引文
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[11]PARK S H,ANTIN N.A discontinuous Galerkin method for seismic soil–structure interaction analysis in the time domain[J].Earthquake Engineering and Structural Dynamic,2004,33:285–293.
[2]LIAO Z P,WONG H L,YANG B P,et al.A transmitting boundary for transient wave analyses[J].Scientia Sinica(Series A),1984,27(10):1063–1076.
[3]DEEKS A J,RANDOLPH M F.Axisymmetric time-domain transmitting boundary[J].Journal of Engineering Mechanics.1994,120(1):25–42.
[4]LIU Jing-bo,LU Yan-dong.A direct method for analysis of dynamic soil-structure interaction based on interface idea[M]//Dynamic Soil-structure Interaction.Beijing:International Academic Publishers,1997,258–273.
[5]邱流潮,刘桦,金峰.二维土–结构地震动力相互作用时域有限元分析[J].工程力学,2006,23(9):114–119.(QIU Liu-chao,LIU Hua,JIN Feng.Time-domain finite-element analysis of two-dimensional seismic soil-structure interactions[J].Engineering Mechanics,2006,23(9):114–119.(in Chinese))
[6]刘云贺,张伯艳,陈厚群.拱坝地震输入模型中黏弹性边界与黏性边界的比较[J].水利学报,2006,37(6):758–763.(LIU Yun-he,ZHANG Bo-yan,CHEN Hou-qun.Comparison of spring-viscous boundary with viscous boundary for arch dam seismic input model[J].Journal of Hydraulic Engineering,2006,37(6):758–763.(in Chinese))
[7]杜修力,赵密.基于黏弹性边界的拱坝地震反应分析方法[J].水利学报,2006,37(9):1063–1069.(DU Xiu-li,ZHAO Mi.Analysis method for seismic response of arch dams in time domain based on viscous-spring artificial boundary condition[J].Journal of Hydraulic Engineering,2006,37(9):1063–1069.(in Chinese))
[8]YAN Jun-yi,JIN Feng,ZHANG Chu-han.A finite element-scaled boundary finite element coupling for soil-structure interactions[C]//Computational Mechanics,WCCM VI in conjunction with APCOM’04,Beijing,2004.
[9]LIN Gao,HU Zhi-qiang.Earthquake safety assessment of concrete arch and gravity dams[J].Earthquake Engineering and Engineering Vibration,2005,4(2):251–264.
[10]陈建云,李健波,林皋,等.结构–地基动力相互作用时域数值分析的显–隐式分区异步长递归算法[J].岩石力学与工程学报,2007,26(12):2481–2487.(CHEN Jian-yun,LI Jian-bo,LIN Gao,et al.A sub-regional explicit-implicit recursive method with mixed step-size strategy in time domain for dynamic structure-foundation interaction analysis[J].Chinese Journal of Rock Mechanics and Engineering,2007,26(12):2481–2487.(in Chinese))
[11]PARK S H,ANTIN N.A discontinuous Galerkin method for seismic soil–structure interaction analysis in the time domain[J].Earthquake Engineering and Structural Dynamic,2004,33:285–293.
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