共查询到20条相似文献，搜索用时 31 毫秒
1.
考虑地震荷载的随机性及强度、频率的非平稳性,基于作者提出的适用于非平稳随机过程的一般随机地震动模型,采用虚拟激励法,建立了非平稳随机地震反应分析方法,并将其应用于某实际均质土坝动力分析中。土石坝及坝基体系采用整体有限元离散,坝体和坝基材料的动力非线性性能以等效线性化方法考虑。首先,基于目标加速度时程的强度和能量信息,确定了作为输入的加速度时—频演变功率谱密度;其次,比较了确定性时程动力分析和非平稳随机分析的结果,探讨了频率非平稳随机地震激励下的土石坝地震反应特性;最后,比较了2种不同坝基条件下的土石坝非平稳随机地震反应,探讨了频率非平稳随机激励下的土石—坝基动力相互作用。分析结果表明：地震动的频率非平稳性对土石坝动力反应有一定影响;坝体—坝基动力相互作用在地震过程中的不同阶段表现有所不同,主震阶段的相互作用显著。 相似文献
2.
A time-domain method for the analysis of arch dam-foundation rock dynamic interaction during earthquake was proposed, and
the dynamic relaxation technique was adopted to obtain the initial static response for dynamic analysis by [Du et al. (2005).
The paper has been contributed to Bulletin of earthquake engineering]. In this paper, a nonlinear explicit method in time
domain considering the opening and closing effect of contact joints on arch dam during earthquake is further proposed by introducing
the dynamic contact force model into the method. The simulation accuracy of dynamic contact force model is verified by comparing
its calculation result and test result of scale model on shaking table. Finally, the influence of joints on the seismic response
of Xiaowan arch dam is studied by the proposed method and some conclusions are given. 相似文献
3.
4.
拱坝横缝影响及有效抗震措施的研究 总被引：6，自引：0，他引：6
大量研究结果和某些拱坝的地震震害表明，横缝对拱坝的地震响应有很大的影响。通过采用非光滑方程组方法以及考虑碰撞时刻动量、动能守恒来模拟横缝所引起的动接触问题，同时为了提高计算效率，采用隐-显式积分方法对坝-基系统的动力平衡方程进行求解。针对在拱坝中上部配筋这一抗震措施，也作了探讨。通过对小湾拱坝的分析，为高拱坝工程抗震措施的选择提供技术依据。 相似文献
5.
Linear finite element analyses are commonly used to simulate the behaviour of gravity dam—foundation systems. However, the foundation is generally unable to develop any significant tensile stresses. Therefore any tension occurring in the vicinity of the dam—foundation interface is largely fictitious. Moreover, the traditional overturning and sliding stability criteria have little meaning in the context of the oscillatory response of dams during earthquakes. In this study, time domain analyses using non-linear contact elements located at the dam—foundation interface have been used to determine the dynamic sliding and uplifting response of gravity dam monoliths considering various elastic foundation properties. The magnitudes of the relative interface displacements, of the percentage of base not in contact (PBNC) and of the compressive stresses at the heel or toe of the dam have been used to monitor the seismic stability. The numerical results have shown that the non-linear behaviour of the dam—foundation interface reduces the seismic response of the system, indicating the possibility of more rational and economical designs. The PBNC was identified as the critical seismic stability response parameter for all analyses except for very flexible foundation conditions where the maximum values of relative interface displacements need to be considered. 相似文献
6.
Dynamic response of dams is significantly influenced by foundation stiffness and dam-foundation interaction. This in turn,
significantly effects the generation of hydrodynamic pressures on upstream face of a concrete dam due to inertia of reservoir
water. This paper aims at investigating the dynamic response of dams on soil foundation using dynamic centrifuge modelling
technique. From a series of centrifuge tests performed on model dams with varying stiffness and foundation conditions, significant
co-relation was observed between the dynamic response of dams and the hydrodynamic pressures developed on their upstream faces.
The vertical bearing pressures exerted by the concrete dam during shaking were measured using miniature earth pressure cells.
These reveal the dynamic changes of earth pressures and changes in rocking behaviour of the concrete dam as the earthquake
loading progresses. Pore water pressures were measured below the dam and in the free-field below the reservoir. Analysis of
this data provides insights into the cyclic shear stresses and strains generated below concrete dams during earthquakes. In
addition, the sliding and rocking movement of the dam and its settlement into the soil below are discussed. 相似文献
7.
8.
Non-uniform ground motions are generated based on a single record available at a site and seismic wave scattering analysis. The Chino Hills 2008 earthquake records at the Pacoima Dam site are used to indicate the accuracy of the method. Dynamic analysis of the Pacoima dam-reservoir-foundation under uniform and non-uniform ground motions is carried out using the EACD-3D2008 software, and the results are compared to recorded responses at different locations on the dam. There is good agreement between computed and recorded displacements of the dam for non-uniform excitation. For uniform excitation, the displacements are underestimated in comparison with those obtained from recorded excitation. Significant intensification of stresses, especially near the foundation, and different patterns of stress distribution are observed for non-uniform excitation in comparison with uniform excitation. For uniform excitation maximum stresses occur in the crown cantilever near the crest, but for non-uniform excitation the maximum stresses occur along the sides and near the foundation. 相似文献
9.
In this study, two different earthquake input models are introduced, i.e. massless foundation model and viscous-spring boundary input model considering radiation damping. Linear elastic and nonlinear contraction joint opening analyses of the 210 m high Dagangshan arch dam under construction in China are performed using the two different earthquake input models. First, the responses of the three-dimensional (3-D) canyon without the dam are analyzed, respectively, with massless-truncated foundation and with viscous-spring boundary; second, linear and nonlinear analyses of the dam–foundation system are performed and compared by using the two input models. Hydrodynamic effects are considered using finite element discretization for incompressible reservoir fluid. It is concluded that stresses and displacements and contraction joint opening in the dam are significantly reduced both in linear and nonlinear analyses when using viscous-spring boundary model. Interestingly, in the case of linear analysis of the Dagangshan, the massless foundation input model with a relatively higher damping ratio of 10% leads to a comparable response of the dam to that using viscous-spring boundary model. In addition, the maximum tensile stresses from nonlinear analysis are 10–25% larger than that of the corresponding linear cases due to a partial release of the arch action. 相似文献
10.
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
11.
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
12.
Several significant parameters that could affect interaction in a dam-foundation system are discussed. These parameters are: (1) Fundamental periods of the dam and the foundation layer. (2) Lateral extent of the dam. (3) The material properties of the dam and the foundation layer. Five cases are analysed to illustrate the influence of these parameters on interaction. An interaction ratio, R1, relating the response of the dam-foundation system at the base of the dam to the free field response is introduced and interaction effects are expressed in terms of this ratio; the smaller this ratio, the less are the interaction effects. For very small values of R1, it is shown that the dam-foundation system could be decoupled The results of the studies presented in the paper suggest that the interaction effects cannot be uniquely related to either the ratio of the period of the dam to the period of the foundation layer, or to the material properties of the dam and foundation layer. However, for the limited number of cases investigated, the interaction effects were found to be uniquely related to the ratio D/B, where D is the depth of the foundation layer and B is the width of the dam section. For values of D/B less than unity, strong interaction effects were obtained and the dam-foundation system could only be analysed as a coupled system. For values of D/B greater than unity, the interaction appeared negligible and the dam and its foundation layer could be decoupled. It should be noted, however, that for very small values of D/B the interaction effects would decrease becaase as D approaches zero, there would be no interaction The use of the interaction ratio, R1, and the parameter D/B should aid in assessing the need for analysing the response of the dam-foundation as a coupled or as a decoupled system. 相似文献
13.
《地震工程与工程振动(英文版)》2015,(3)
A seismic stability assessment of arch dam-foundation systems is presented using a comprehensive approach,in which the main factors that significantly influence the seismic response of an arch dam-foundation system are considered.A large scale finite element model with over 1 million degrees of freedom is constructed for the Baihetan arch dam(289 m high),which is under construction in the Southwest of China.In particular,the complicated geological conditions with faults intersecting interlayer shear weakness zones at the dam base and the dam abutment resisting force body is modeled in the analysis.Three performance indices are adopted to assess the seismic stability of the arch dam.The results demonstrate that the opening of the joints of the Baihetan arch dam is small and the water stop installed between the joints would not be torn during a design earthquake.The yielding formed in the interface between the dam and foundation does not reach the grouting curtain that would remain in an elastic state after an earthquake.The yielding zones occurring on the upper portion of the dam faces extend 1/8 thickness of block section into the dam body and thus cantilever blocks need not be concerned with sliding stability.The faults and interlayer shear weakness zones in the near field foundation exhibit severe yielding,and a potential sliding surface is penetrated.Although the factor of safety against sliding of the surface fluctuates with a decreased trend during an earthquake,the minimum instantaneous value reaches 1.02 and is still larger than 1.0.Therefore,a conclusion is drawn that the Baihetan arch dam-foundation system will remain stable under the design earthquake. 相似文献
14.
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
15.
A numerical method, the hybrid frequency-time domain (HFTD) procedure, is used to compute the earthquake response of concrete gravity dams, including sliding along the interface between the dam base and the foundation rock. The solution procedure accounts for the non-linear base sliding behaviour and the frequency-dependent response of the impounded water and flexible foundation rock. A Coulomb friction model represents the force-displacement relationship for sliding at the base interface. Using the solution procedure, an analysis of a typical dam (122 m high) shows that base sliding will occur during a moderate earthquake but the sliding displacement will be a tolerable amount when dam-foundation rock interaction is considered. 相似文献
16.
In this paper, a study on the transient response of an elastic structure embedded in a homogeneous, isotropic and linearly elastic half-plane is presented. Transient dynamic and seismic forces are considered in the analysis. The numerical method employed is the coupled Finite-Element–Boundary-Element technique (FE–BE). The finite element method (FEM) is used for discretization of the near field and the boundary element method (BEM) is employed to model the semi-infinite far field. These two methods are coupled through equilibrium and compatibility conditions at the soil–structure interface. Effects of non-zero initial conditions due to the pre-dynamic loads and/or self-weight of the structure are included in the transient boundary element formulation. Hence, it is possible to analyse practical cases (such as dam–foundation systems) involving initial conditions due to the pre-seismic loads such as water pressure and self-weight of the dam. As an application of the proposed formulation, a gravity dam has been analysed and the results for different foundation stiffness are presented. The results of the analysis indicate the importance of including the foundation stiffness and thus the dam–foundation interaction. 相似文献
17.
A rigorous analytical solution is developed for the lateral linear shear response of embankment dams in semi-cylindrical valleys. Closed-form algebraic expressions are presented pertaining to both free and base-induced oscillations, and extensive parametric and comparative studies elucidate the prominent effects of canyon geometry (shape and aspect ratio) on dynamic response. Harmonic steady-state as well as earthquake-induced accelerations, displacements and shear strains in the dam are studied and compared with those obtained from 3-Dimensional analyses for other canyon geometries, as well as from 2-Dimensional (2-D) analyses of the dam mid-section. It is shown that such 2-D analyses may provide significantly lower values of near-crest accelerations, but slightly higher values of shear strains and stresses than the 3-D analyses. The proposed method of analysis is at least three orders of magnitude less expensive than other presently available numerical procedures. 相似文献
18.
The linear response of a selected arch dam to harmonic upstream, vertical or cross-stream ground motion is presented for a wide range of the important system parameters characterizing the properties of the dam, foundation rock, impounded water and reservoir boundary materials. Based on these frequency-response functions, the dam-foundation rock interaction effects in the dynamic response of arch dams are investigated. 相似文献
19.
本文将随机振动的虚拟激励法与拱坝-地基动力相互作用FE-BE-IBE时域模型结合，发展了一个可以考虑多维随机地震动作用下的拱坝动力响应计算模型，并用Monte Garlo方法对模型进行了验证，计算结果表明，地震动分量的相关性对结构的动力响应存在一定影响，合理考虑地震动各方向分量的相关性可以更好地计算实际地震作用下的拱坝动力响应。 相似文献