Seismic Response Of Arch Dams Research Articles

Effect of valley topography on dynamic response of arch dams

Arch dams are typically built in the mountain and gorge regions with complex terrain. In the current engineering practice, foundation models are commonly simplified as the half-space with the canyon of regular geometry. The complex topography conditions above the dam crest are neglected. This study investigates the effect of realistic valley topography on the dynamic response of arch dams. The direct finite element method is generalized and applied to the dam-reservoir-foundation system with realistic valley topography. The input ground motions are transformed into the effective earthquake loads at the truncated boundaries by performing several dynamic reaction calculations using one-dimensional (1D) and two-dimensional (2D) auxiliary finite element models. The effect of valley topography on the seismic response of the Baihetan arch dam is evaluated as a case study. Results indicate that the valley topographic irregularities significantly influence the dynamic responses of the arch dam, including relative displacement and stress distribution. Notably, the valley topography effect on the seismic response of arch dams depends on the incident ground motions and is hardly predicted in advance, demonstrating the necessity to account for the realistic topography conditions.

A rapid and automated analysis procedure for seismic response of arch dams

The seismic safety of arch dams has long been a focal point of research. Due to the complexity of modeling and computation, analyzing the seismic response of arch dams using traditional finite element methods requires a considerable amount of time. In the event of a sudden earthquake, it is challenging to quickly obtain stress analysis results or conduct a safety assessment. To address these issues, a rapid and automated analysis procedure is proposed in this paper, providing seismic response of arch dams within hours after an earthquake. The procedure includes a pre-processing program, a computing program EACD-3D-2008, and a post-processing program, achieving a fully automated process from generating non-uniform earthquakes to analyzing dam dynamic responses and visualizing computation results. As a case study, the 294.5 m high Xiaowan arch dam in southwest China is analyzed, which is equipped with strong motion instruments that have recorded several small earthquakes. The case study revealed that accounting for the non-uniformity of the earthquake significantly improves simulation results, with maximum principal stresses typically occurring near the dam-foundation rock interface. Additionally, the procedure effectively compensates for missing data, allowing for the successful supplementation of the missing acceleration records. For stronger earthquakes, high-stress regions are clearly displayed in the result visualization, providing an effective reference for safety assessment. The case study validated the accuracy and wide applicability of the procedure, demonstrating its potential to offer valuable insights for similar analyses in various engineering projects.

Effect of attached outlets on the dynamic response of arch dams

Attached outlets are integral components of arch dams to discharge flood. However, they are usually neglected in the current seismic analysis of arch dams for simplicity. This paper aims to analyze the effect of attached outlets on the nonlinear seismic response of arch dams. For this purpose, a 235 m high arch dam is analyzed as a case study. The results indicate that the effect of attached outlets on the seismic response of arch dams depends on the ground motion intensity. For the ground motions with a low peak ground acceleration (PGA), the effect of attached outlets on the concrete damage is slight and local, which is consistent with the existing perception. However, as the ground motion intensity increases, their effect extends to the entire dam body. In contrast, the influence of attached outlets on the joint opening is typically observed at the middle contraction joints. Furthermore, the model analysis demonstrates that the inertia effect of attached structures is the primary contribution to these phenomena. Finally, a simplified simulation approach is used for incorporating the influence of attached outlets by coalescing the mass to the dam surface.

Nonlinear seismic response of arch dams considering joint opening effects and boundary conditions of discontinuous foundation

Nonlinear seismic response of arch dams considering joint opening effects and boundary conditions of discontinuous foundation

Study on the dynamic interaction between an arch dam and its appurtenant structures

This paper aims to analyze the effect of appurtenant structures on the seismic response of arch dams. For this purpose, a fine-grade finite element model is developed for the Sanhekou dam in China as a case study, which includes the discharge structure, the intake tower, the elevator shaft, and the viewing platform. The results indicate that different appurtenant structures have different influences on the seismic response of the dam. The crest spillways and the low-level outlets perforated in the dam body, significantly affect the seismic response of the local region of the arch dam body, while the appurtenant structures extending from the dam body, such as the intake tower, the elevator shaft, and the sightseeing buildings, have little influence on the seismic response of the dam body. In addition, the local vibration amplitudes of the high cantilever water inlet and the high-rise elevator shaft are significant, and thus they may be damaged under seismic loads.

The effect of non-uniformity in ground motions on the seismic response of arch dams

Recorded ground accelerations at various locations of Karun III Dam during November 20, 2007, were recorded by an array of accelerometers located on the dam. In terms of amplitude and phase, these accelerations show non-uniformities in different elevations. In this paper, the effect of these non-uniform ground motions on the seismic response of the dam taking dam-reservoir-foundation interaction into account is investigated. The EACD-3D-2008 finite element program and ABAQUS Software are used for carrying out the seismic analyses. For this purpose, time histories of the earthquake accelerations are interpolated at nodal points located on the dam foundation interface. The analysis has been repeated, considering the common assumption of uniform ground motions. Comparing the results obtained from these two analyses reveals that the computed displacements in the crest due to the spatially varying excitations are in more conformity with the recorded information. Moreover, neglecting the non-uniform nature of ground motions in the model leads to underestimating the tensile stress values within the dam body.

The Effect of Shear Sliding of Vertical Contraction Joints on Seismic Response of High Arch Dams with Fine Finite Element Model

The contraction joints of arch dams with and without shear keys are simplified to be with no‐slip condition and with relative sliding condition, respectively. Based on the Lagrange multiplier method, a contact model considering the manner of independent cantilever dead load type with no‐slip condition and relative sliding condition is proposed to model the nonlinearities of vertical contraction joins, which is special to the nonlinear analysis of arch dams considering the manner of dead load type. Different from the conventional Gauss iterative method, the strategy of the alternating iterative solution of normal force and tangential force is employed. The parallelization based on overlapping domain decomposition method (ODDM) and explicit message passing using distributed memory parallel computers is employed to improve the computational efficiency. An existing high arch dam with fine finite element model is analyzed to investigate the effect of shear sliding of vertical joints on seismic response of the arch dam. The result shows that the values of maximum principal tensile stress under relative sliding condition are significantly greater than those under no‐slip condition.

A procedure to predict the precise seismic response of arch dams in time domain using boundary element formulation

In this context, a new boundary element algorithm based on the time-convoluted traction kernels is employed to evaluate the spatially varying earthquake ground motions of the Pacoima dam in the USA subjected to SH, SV and P incident waves. An accurate three-dimensional (3D) model of the dam canyon is implemented into the computer code BEMSA to investigate the seismic response of the dam. The analyses are performed in time domain with a linearly elastic constitutive model for the medium. This modeling procedure has been validated by the results reported in the existing literature. According to the results of this study, the response of the dam to earthquake waves is generally influenced by predominant frequency of the incident motion, surface topography, relative distance of observation points, and type of the incident seismic wave. For the cases considered, the incident SV wave has led to the maximum amplification of incident motions, especially at the left side of the dam. The results indicate that the proposed procedure can be employed for accurate prediction of a dam response during an earthquake.

Effect of foundation models on seismic response of arch dams

Simulation of the infinite foundation is a key issue in the seismic response analysis of high dams. This paper studies how the major characteristics of foundation models influence the nonlinear dynamic response of arch dams when the radiation damping effect is taken into account. The nonlinear dynamic responses of the 217 m high Yebatan arch dam under construction in China is performed as a numerical example. Several key factors, including truncated size, material damping and non-uniformity of the foundation, are analyzed comprehensively. The results show that the material damping and the size of the foundation affect the dynamic response of the dam when the incident wave method is used. Neglect of the material damping of the foundation is proposed to solve this problem, and its rationality is verified. In addition, the results show that the realistic non-uniformity of the foundation should be considered in the earthquake response of arch dams.

Hydrodynamic pressures in contraction joints including waterstops on seismic response of high arch dams

In the present paper, the effects of hydrodynamic pressures in contraction joints, on seismic response of arch dams are investigated. For this purpose an algorithm for applying the hydrodynamic pressures in open contraction joints is developed. The dam body material is assumed to have linear elastic behavior and all the contraction joints are simulated as reported in as-built drawings. In addition, the reservoir medium is taken to be compressible and the rock foundation is modeled as a mass-less flexible medium. The coupled system of dam-reservoir-foundation is analyzed utilizing simultaneous approach and NEWMARK-β method is used for integration in time domain. The effects of hydrodynamic pressure during seismic excitation on joints opening/sliding, stress distribution patterns within the dam body and on the crest displacement time history are studied. It is found that for a typical high concrete arch dam, the hydrodynamic pressure in the contraction joints are not affected much by in the present of waterstops. Taking these pressures into account leads to significant consequences on the dam behavior; and it must be considered, as the joint opening in high concrete arch dams is a common phenomenon even during low to medium ground shakings.

Seismic plastic–damage analysis of mass concrete blocks in arch dams including contraction and peripheral joints

Seismic nonlinear analysis of concrete arch dams is a topic having been extensively studied in the last two decades. Due to the existence of different joints within the body of arch dams, the discrete crack (DC) approach utilizing interface elements for the joints is the most realistic method. In fact, it could be the first step to assess the seismic safety of an arch dam. Furthermore, since the mass concrete blocks may crack due to severe ground excitations, a plastic–damage (PD) model well capturing stiffness degradation and permanent deformation due to tensile cracking and compressive crushing might be needed. In this study, a special finite element program called SNACS is developed based on the combined discrete crack and plastic–damage (DC–PD) technique. The dam–reservoir interaction as an important factor affecting the seismic response of arch dams is also treated by the Lagrangian–Eulerian formulation. The joints modeling strategy adopted herein is addressed first and then, a brief review of the plastic–damage model proposed by Lee and Fenves and extended herein to 3-D space is presented. Afterwards, the nonlinear seismic analysis of a typical thin arch dam is performed based on the combined approach and the response is compared with the results of each method. It is emphasized that employing the combined DC and PD models gives more reliable and consistent response in comparison with using DC or PD approaches applied alone. Therefore, the DC–PD technique could be considered as a major step toward a more accurate seismic safety evaluation of concrete arch dams.

Arrival direction effects of travelling waves on nonlinear seismic response of arch dams

The aim of this study is to investigate arrival direction effects of travelling waves on non-linear seismic response of arch dams. It is evident that the seismic waves may reach on the dam site from any direction. Therefore, this study considers the seismic waves arrive to the dam site with different angles,

Influence of reservoir geometry and conditions on the seismic response of arch dams

An analysis of the influence that reservoir levels and bottom sediment properties (especially on the degree of saturation) have on the dynamic response of arch dams is carried out. For this purpose, a Boundary Element Model developed by the authors that allows the direct dynamic study of problems that incorporate scalar (dammed up water), viscoelastic (dam and soil site) and poroelastic media (bottom sediments in the reservoir) is used. All of the regions are discretized using boundary elements, later formulating equations of compatibility and equilibrium that allow their interaction to be rigorously established. The seismic excitation consists in plane longitudinal waves (P waves) and shear waves (S waves) impinging the dam site with an angle of vertical incidence. The analysis is carried out in the frequency domain, and the time response is obtained, for synthesized artificial accelerograms defined in terms of the elastic response spectrum taken from Eurocode 8, using a FFT algorithm. The variables used to characterize the response are: Amplitude of the complex-valued frequency-response function, acceleration response spectra and the integral of velocity of points located at the structure. These variables clearly indicate the importance that the factors analyzed have on the dynamic response.

Research on Influence of Sediments Mechanical Parameters of Seismic Arch Dams

The problem of sediments on seismic response of arch dams was not solved. Thus pressure wave formula of saturated porous fluid-solid two-phase medium was applied from the Bait’s consolidation theory, and was determined the seismic response magnitude of sediment on arch dam. And the method was applied to analyze the influence of sediments thickness, cohesion and friction angle on dam seismic response. The result shows sediments is relatively obvious on arch dam seismic response.

Spatial variation input effects on seismic response of arch dams

In the present paper, the seismic response of an arch dam subjected to spatial variation of ground motions along the interface with its foundations is investigated. Recorded ground accelerations at the dam foundation interface of an arch dam were used for the purpose of this investigation. Topographic amplification between various points of the interface was studied by obtaining ratios of the response spectral displacement and spectral pseudo acceleration. Time shift and amplification between stations show the nonuniform nature of ground motions for large structures like dams. Recorded ground accelerations were interpolated for different nodes of the finite element model. The seismic responses of the Karun III dam subjected to multiple support excitations are determined. The results show that nonuniform ground acceleration can have extensive effects on dam behavior and can increase the responses. Pseudo static displacement is the dominant part of total displacement for points near the dam foundation interface; however, dynamic displacement is more significant for the middle part of the dam.

Seismic response control of high arch dams including contraction joint using nonlinear super-elastic SMA damper

In this study, the shape memory alloy (SMA) restrainer bars utilized to reduce the seismic response of arch dams with vertical contraction joints were investigated. The SMA damper model and the nonlinear behavior of arch dams affected by contraction joint opening/closing during earthquakes were simulated in ANSYS. Moreover, the nonlinear damping control principle and method were discussed. The effectivity of the SMA restrainer bars in arch dams was assessed through comparing with a traditional measure of reinforced steel across contraction joints. The SMA restrainer bars were effective in limiting the relative openings of the contraction joints and reducing the seismic acceleration. In addition, the new SMA vibration damper devices of arch dams are simple and easy to install.

Three‐dimensional models of reservoir sediment and effects on the seismic response of arch dams

AbstractThe important effects of bottom sediments on the seismic response of arch dams are studied in this paper. To do so, a three‐dimensional boundary element model is used. It includes the water reservoir as a compressible fluid, the dam and unbounded foundation rock as viscoelastic solids, and the bottom sediment as a two‐phase poroelastic domain with dynamic behaviour described by Biot's equations. Dynamic interaction among all those regions, local topography and travelling wave effects are taken into account. The results obtained show the important influence of sediment compressibility and permeability on the seismic response. The former is associated with a general change of the system response whereas the permeability has a significant influence on damping at resonance peaks. The analysis is carried out in the frequency domain considering time harmonic excitation due to P and S plane waves. The time‐domain results obtained by using the Fourier transform for a given earthquake accelerogram are also shown. The possibility of using simplified models to represent the bottom sediment effects is discussed in the paper. Two alternative models for porous sediment are tested. Simplified models are shown to be able to reproduce the effects of porous sediments except for very high permeability values. Copyright © 2004 John Wiley & Sons, Ltd.

Influence of effective parameters of non-orthogonal smeared crack approach in seismic response of concrete arch dams

A rigorous and relatively efficient algorithm based on the non-orthogonal smeared crack approach is coded in a special finite element program to study the seismic response of arch dams. The formulation is briefly presented. The 130 m high Shahid Rajaee arch dam in Iran subjected to the Friuli-Tolmezzo earthquake is selected to present a practical application of the technique. Under the same geometry and loading conditions, six nonlinear analyses with different parameters are performed, and the results are compared with each other and a linear case. The varied parameters include secant and elastic unloading–reloading options, threshold angle, and tensile strength of the material. It is concluded that the non-orthogonal smeared crack approach can redistribute the state of stresses and produces a more realistic profile of stresses in the dam. A drift in the crest displacements forms the prominent characteristics of the cracking behavior. The results also suggest that the dam can suffer significant cracking during a strong earthquake and still remain stable. Moreover, the influences of the mentioned parameters in the seismic response of the dam are comprehensively discussed.Key words: nonlinear dynamic analysis, concrete arch dam, smeared crack approach.

Effects of Space Distribution of Excitation on Seismic Response of Arch Dams

The effects of the ground motion spatial variation and of the canyon geometry on the dynamic response of arch dams during the event of an earthquake is studied in this paper. The seismic response of a dam subject to time harmonic longitudinal, shear, and Rayleigh waves impinging the dam site from different directions is analyzed. Several canyon and reservoir geometries are considered. A three-dimensional boundary element model which allows for the rigorous representation of the dynamic interaction between the dam, the foundation rock, and the water is used. The foundation rock is modeled as a uniform viscoelastic boundless domain where the incident traveling wave field is defined by its analytical expression, which may include any spatial variation. The obtained results show the importance of three-dimensional effects which are many times neglected.

Seismic response of arch dams considering infinite radiation damping and joint opening effects

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.