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1.
A nonlinear finite element model for earthquake response analysis of arch dam–water–foundation rock systems is proposed in this paper. The model includes dynamic dam–water and dam–foundation rock interactions, the opening of contraction joints, the radiation damping of semi‐unbounded foundation rock, the compressibility of impounded water, and the upstream energy propagating along the semi‐unbounded reservoir. Meanwhile, a new equivalent force scheme is suggested to achieve free‐field input in the model. The effects of the earthquake input mechanism, joint opening, water compressibility, and radiation damping on the earthquake response of the Ertan arch dam (240 m high) in China are investigated using the proposed model. The results show that these factors significantly affect the earthquake response of the Ertan arch dam. Such factors should therefore be considered in the earthquake response analysis and earthquake safety evaluation of high arch dams. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
2.
A dynamic overloading model test has been carried out on a shaking table for an arch dam of 278 m in height to investigate its behaviours under strong earthquake. The model system included the arch dam with contraction joints, part of reservoir, partial foundation rock with topographic feature near the dam. A damping boundary consisting of viscous liquid has been used to simulate the effect of dynamic energy emission to far field, which made the dynamic interaction between dam and foundation in model arch dam system be represented properly. Three sets of different seismic waves of design level have been used as the input to investigate the difference in the responses of arch dam. Artificial waves of different levels have been used to verify the behaviours of arch dam under seismic overloading. Since the opening of joints during strong earthquake reduced the response acceleration and tensile arch stress, cantilever stress on downstream face exceeded the tensile strength first for the model dam. And the arch dam responded in a non‐linear way when input seismic load increased. Some cracks appeared near abutments, and the damage made the natural frequency of arch dam to drop obviously, but the static function did not seem to change for the model tested. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
3.
The overall damping of linear arch dam-water-foundation rock systems depends on the material damping of dam concrete, the material and radiation damping of semi-unbounded foundation rock, and the dam-water interaction. In this paper, the effective damping ratio of these factors is separately evaluated for Mauvoisin arch dam in Switzerland to quantitatively discuss their contributions, and to guide the damping selection in the numerical analysis. This paper also aims to investigate if the material and radiation damping of the foundation rock can be replaced by increasing the material damping of the dam to simplify numerical analysis models. The seismic responses of Mauvoisin arch dam are analyzed using the semi-unbounded and massless foundation models, respectively. The results show that the overall effective damping ratio of the system can be approximately expressed as the summation of the individual effective damping and thus the increased material damping of the dam can approximate the material and radiation damping of the semi-unbounded foundation rock. 相似文献
4.
One of the main concerns in using commercial software for finite element analyses of dam-foundation-reservoir systems is that the simplifying assumptions of the massless foundation are unreliable. In this study, an appropriate direct finite element method is introduced for simulating the mass, radiation damping and wave propagation effect in foundations of damfoundation-reservoir systems using commercial software ABAQUS. The free-field boundary condition is used for modeling the semi-infinite foundation and radiation damping, which is not a built-in boundary condition in most of the available commercial software for finite element analysis of structures such as ANSYS or ABAQUS and thus needs to be implemented differently. The different mechanism for modeling of the foundation, earthquake input and far-field boundary condition is described. Implementation of the free-field boundary condition in finite element software is verified by comparing it with analytical results. To investigation the feasibility of the proposed method in dam-foundation-reservoir system analysis, a series of analyses is accomplished in a variety of cases and the obtained results are compared with the substructure method by using the EAGD-84 program. Finally, the massed and massless foundation results are compared and it is concluded that the massless foundation approach leads to the overestimation of the displacements and stresses within the dam body. 相似文献
5.
Seismic responses of a 292‐m high arch dam were studied by experiment on a shaking table. The model system included the arch dam with contraction joints, a part of a reservoir, and a partial foundation with a topographic feature near the dam. Potential rock wedges on the abutments and the mechanical properties including uplift on the kinematic planes were carefully simulated. A damping boundary consisting of a viscous liquid was introduced to simulate the effect of dynamic energy emission to far field, which made the dynamic interaction between the dam and the foundation be adequately represented in the model test of an arch dam system. Dynamic responses of the arch dam system under a sequence of seismic loadings in increasing strength were examined. Eleven cracks or overstresses on the model dam due to the earthquake excitations were observed, and consequently, its natural frequency dropped by about 14%, but the model dam was stable under the hydrostatic load of the impounded water after the test. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
6.
Seismic response of arch dams considering infinite radiation damping and joint opening effects 总被引：3，自引：0，他引：3
Effects of two important factors on earthquake response of high arch dams are considered and combined into one program. These
factors are: effects of radiation damping of the infinite canyon and local non-linearity of the contraction joint opening
between the dam monoliths. For modeling of rock canyon, the discrete parameters are obtained based on a curve fitting, thus
allowing the nonlinear dam system to be solved in the time domain. The earthquake uniform free-field input at the dam-canyon
interface is used. An engineering example is given to demonstrate the significant effects of the radiation damping on the
structure response. 相似文献
7.
Different procedures are compared for the three-dimensional seismic cracking analysis of gravity and arch dams during strong earthquakes. The fracture procedures include the extended finite element method with cohesive constitutive relations, crack band finite element method with plastic-damage relations, and the finite element Drucker−Prager elasto-plastic model. These procedures are used to analyze the nonlinear dynamic response of Koyna dam to the 1967 Koyna earthquake and the seismic cracking of the Dagangshan arch dam subjected to design earthquake. The cracking process and profiles of the two dams using the three different procedures are compared. The applicability and the suitability of the three procedures for seismic cracking analysis of gravity and arch dams are discussed. 相似文献
8.
9.
Nonlinear seismic response analysis of arch dam-foundation systems- part I dam-foundation rock interaction 总被引：1，自引：0，他引：1
The arch dam–foundation rock dynamic interaction and the nonlinear opening and closing effects of contact joints on arch dam
are important to the seismic response analysis of arch dams. Up to date, there is not yet a reasonable and rigorous procedure
including the two factors in seismic response analysis. The methods for the analysis of arch dam–foundation rock dynamic interaction
in frequency domain are not suitable to the problem with nonlinear behaviors, in this paper, so an analysis method in time
domain is proposed by combining the explicit finite element method and the transmitting boundary, and the dynamic relaxation
technique is adopted to obtain the initial static response for dynamic analysis. Moreover, the influence of arch dam–foundation
dynamic interaction with energy dispersion on seismic response of designed Xiaowan arch dam in China is studied by comparing
the results of the proposed method and the conventional method with the massless foundation, and the local material nonlinear
and nonhomogeneous behaviors of foundation rock are also considered. The reservoir water effect is assumed as Westergaard
added mass model in calculation. The influence of the closing–opening effects of contact joints of arch dam on the seismic
response will be studied in another paper. 相似文献
10.
本文通过成层状地基地震动输入计算方法得到覆盖层边界自由场运动,采用粘弹性边界,考虑地基辐射阻尼效应及坝体和地基的接触非线性,针对强震区深厚覆盖层场地重力坝开展线性和非线性动力时程分析研究,结合需求能力比DCR评估其抗震性能。由线弹性动力时程分析可知,在运行基准地震OBE作用下,重力坝坝体应力均在允许范围内,其抗滑稳定安全系数不能满足要求;由非线性动力分析可知,在OBE和最大设计地震MDE作用下,重力坝发生较大滑动位移。通过在重力坝坝体下游坝后回填土加强重力坝抗震稳定性,结果表明,下游坝后回填土可有效减小坝体滑动位移,加强其抗震稳定性。本文针对深厚覆盖层场地重力坝开展的抗震安全研究为抗震设计提供了科学依据,为强震区深厚覆盖层场地重力坝的抗震分析提供参考。 相似文献
11.
有缝拱坝-地基系统非线性地震波动反应分析方法 总被引：12，自引：3，他引：9
拱坝坝体中缝界面在地震作用下的开、合模拟对拱坝地震反应有重要影响。目前在拱坝地震反应分析中应用的一些模型,如Ｆｅｎｖｅｓ模型、Ｄｏｗｌｉｎｇ的三参数模型,存在对缝界面的接触状态模拟精度不高的问题,这对于准确评价工程上关心的缝界面最大张开率是不足的。此外,坝基中存在的断层、节理、裂隙待软弱夹层的非线性力学特性和无限地基能量辐射作用对拱坝地震反应也有重要影响。在拱坝地震反应分析中同时考虑这三种影响因素 相似文献
12.
Murat Emre Kartal Alemdar Bayraktar Hasan Basri Başağa 《Soil Dynamics and Earthquake Engineering》2010
In this study, failure probability of the concrete slab on concrete-faced rockfill (CFR) dams with welded and friction contact is investigated under earthquake effects by reliability analysis. For this purpose, Torul CFR dam is selected as an example and numerical solutions are performed by considering combination of reliability analysis–finite element method. 1992 Erzincan earthquake acceleration record is used in the finite element analysis considering deconvolved-base rock input model. In this model, the ground motion to be applied to the foundation base rock is obtained by deconvolution of the free-field surface record. In the materially nonlinear analysis, Drucker–Prager model is used for concrete slab and multi-linear kinematic hardening model is utilized for rockfill. Geometrically nonlinearity is also taken into account. Viscous boundary conditions are defined in the finite element model for both foundation soil and reservoir water. The hydrodynamic pressure of the reservoir water is considered using 2D fluid finite elements based on the Lagrangian approach. Both welded contact and friction contact based on the Coulomb’s friction law are defined in the structural connections. Improved Rackwitz–Fiessler method is used with response surface method in the reliability analysis. The tensile and compression strengths of the concrete slab are utilized in the implicit limit state functions considering various thicknesses. The probability of failure of the most critical points in the concrete slab is obtained. According to this study, the probabilities of failure obtained from the CFR dam including friction contact are lower. When the welded contact is considered in joints, the probability of failure of the concrete slab is 1 due to tensile stress limit state and compression stress limit state only if concrete slab is linear. The most critical probability of failure of the concrete slab appears in the case that the concrete slab is linear and rockfill is materially nonlinear. The probability of failure of the concrete slab decreases if the nonlinearity of the concrete is considered. Also, hydrodynamic pressure decreases the reliability of the concrete slab. 相似文献
13.
R. J. Cmara 《地震工程与结构动力学》2000,29(4):441-460
This paper presents a method for coupled arch dam–foundation–reservoir seismic behaviour analysis. The dam is discretized by finite elements (FE) and the foundation and reservoir are discretized by boundary elements (BE). The opening of contraction joints and the spatial variability of the seismic action is taken into account. The study of Pacoima dam by this method is also presented. The computed results show that no cracks were to be expected due to the vibrations induced during the Feb. 9, 1971 San Fernando earthquake. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
14.
The energy transmitting boundary used in programs such as FLUSH and ALUSH is a very accurate and useful technique for the earthquake response analysis of soil–structure interaction systems. However, it is applicable only to linear analyses or equivalent linear analyses, because it can be calculated only in the frequency domain. The author has proposed methods for transforming frequency-dependent impedance into the time domain. In this paper, an earthquake response analysis method for a soil–structure interaction system, using the energy transmitting boundary in the time domain, is proposed. First, the transform of the transmitting boundary matrices to the time domain using the methods proposed by the author is studied. Then, linear and nonlinear time history earthquake response analyses using the boundary are performed. Through these studies, the validity and efficiency of the proposed methods are confirmed. 相似文献
15.
Masoud Moghaddasi Misko Cubrinovski J. Geoff Chase Stefano Pampanin Athol Carr 《地震工程与结构动力学》2011,40(2):135-154
Complex seismic behaviour of soil–foundation–structure (SFS) systems together with uncertainties in system parameters and variability in earthquake ground motions result in a significant debate over the effects of soil–foundation–structure interaction (SFSI) on structural response. The aim of this study is to evaluate the influence of foundation flexibility on the structural seismic response by considering the variability in the system and uncertainties in the ground motion characteristics through comprehensive numerical simulations. An established rheological soil‐shallow foundation–structure model with equivalent linear soil behaviour and nonlinear behaviour of the superstructure has been used. A large number of models incorporating wide range of soil, foundation and structural parameters were generated using a robust Monte‐Carlo simulation. In total, 4.08 million time‐history analyses were performed over the adopted models using an ensemble of 40 earthquake ground motions as seismic input. The results of the analyses are used to rigorously quantify the effects of foundation flexibility on the structural distortion and total displacement of the superstructure through comparisons between the responses of SFS models and corresponding fixed‐base (FB) models. The effects of predominant period of the FB system, linear vs nonlinear modelling of the superstructure, type of nonlinear model used and key system parameters are quantified in terms of different probability levels for SFSI effects to cause an increase in the structural response and the level of amplification of the response in such cases. The results clearly illustrate the risk of underestimating the structural response associated with simplified approaches in which SFSI and nonlinear effects are ignored. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
16.
This paper focuses on analyzing the nonlinear seismic response of high‐arch dams with cantilever reinforcement strengthening. A modified embedded‐steel model is presented to evaluate the effects of the strengthening measure on alleviating the extension and opening of cracks under strong earthquakes. By stiffening reinforced steel, this model can easily consider the steel–concrete interaction for lightly reinforced concrete (RC) members without the need of dividing them into RC and plain concrete zones. The new tensile constitutive relations of reinforced steel are derived from the load–deformation relationship of RC members in direct tension. This model has been implemented in the finite element code and its applicability is verified by two numerical simulations for RC tests. Subsequently, numerical analyses for a 210‐m high‐arch dam (Dagangshan arch dam) are conducted with and without the presence of cantilever reinforcement. Numerical results show that reinforcement strengthening can reduce the nonlinear response of the arch dam, e.g. joint opening and crest displacement, and limit the extension and opening width of concrete cracks. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
17.
The effects of incoherency and wave-passage on the nonlinear responses of concrete arch dams are investigated in this study. A double curvature arch dam is selected as a numerical example. The reservoir is modeled as a compressible material and the foundation is modeled as a massless medium. Ground motion time-histories are artificially generated using the Monte Carlo simulation approach. Four different finite element models (FEM) are considered: uniform excitation; incoherence effect; wave passage effect; and both incoherence and wave passage effects. It was revealed that modeling multiple-supports excitation could have a significant impact on the structural response of the dam by inducing a pseudo-static effect. Also, it was concluded that the coherency effect overshadows the wave passage effect and the results obtained from non-uniform excitation of FEM, including the wave passage effect, is close to the results of the FEM when it is uniformly excited. 相似文献
18.
Yasemin Bilici Alemdar Bayraktar Kurtuluş Soyluk Kemal Haciefendioğlu Şevket Ateş Süleyman Adanur 《Soil Dynamics and Earthquake Engineering》2009
In this paper, stochastic dynamic responses of dam–reservoir–foundation systems subjected to spatially varying earthquake ground motions are investigated using the displacement-based fluid finite elements. For this purpose, variable-number-node two-dimensional (2D) fluid finite elements based on the Lagrangian approach is programmed in FORTRAN language and incorporated into a computer program SVEM, which is used for stochastic dynamic analysis of solid systems subjected to spatially varying earthquake ground motion. The spatially varying earthquake ground motion model includes incoherence, wave-passage and site-response effects. The incoherence effect is examined by considering the Harichandran and Vanmarcke coherency model. The effect of the wave passage is investigated by using various wave velocities. Homogeneous medium and firm soil types are selected for considering the site-response effect where the foundation supports are constructed. The Sar?yar concrete gravity dam, constructed in Turkey is selected for numerical example. The ground motion is described by filtered white noise and applied to each support point of the 2D finite element model of the dam–reservoir–foundation system. The record of Kocaeli earthquake in 1999 is used in the analyses. Displacements, stresses and hydrodynamic pressures occurring on the upstream face of the dam are calculated for four cases. It is concluded that spatially varying earthquake ground motions have important effects on the stochastic dynamic response of dam–reservoir–foundation systems. 相似文献
19.
Based on a Chinese national high arch dam located in a meizoseismal region, a nonlinear numerical analysis model of the damage and failure process of a dam-foundation system is established by employing a 3-D deformable distinct element code(3DEC) and its re-development functions. The proposed analysis model considers the dam-foundation-reservoir coupling effect, infl uence of nonlinear contact in the opening and closing of the dam seam surface and abutment rock joints during strong earthquakes, and radiation damping of far fi eld energy dissipation according to the actual workability state of an arch dam. A safety assessment method and safety evaluation criteria is developed to better understand the arch dam system disaster process from local damage to ultimate failure. The dynamic characteristics, disaster mechanism, limit bearing capacity and the entire failure process of a high arch dam under a strong earthquake are then analyzed. Further, the seismic safety of the arch dam is evaluated according to the proposed evaluation criteria and safety assessment method. As a result, some useful conclusions are obtained for some aspects of the disaster mechanism and failure process of an arch dam. The analysis method and conclusions may be useful in engineering practice. 相似文献
20.
有横缝拱坝的非线性动力模型试验和计算分析研究 总被引：12，自引：0，他引：12
本文通过在大型三向地震模拟振动台上进行的设置伸缩横缝的某拱坝非线性动力模型试验，应用非线性有限元动力分析程序同时进行计算分析，全面系统地研究了拱坝横缝对坝体动力特性和地震反应的影响，并对计算程序进行了改进。试验与计算结果相互印证，验证了试验成果的可靠性和计算分析模型、计算程序与计算结果的合理性。 相似文献