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Seismic analyses of concrete gravity dams are usually idealized as two-dimensional structures with a massless foundation in present design procedure. But for gravity dams built in narrow valleys or on sites of very high seismicity, however, interaction between adjacent blocks may influence the seismic responses significantly. Dynamic interaction be...
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Context 1
... 11 and 12 are the distribution of maximum principal stresses on the dam. Figures 13 and 14 are the distribution of minimum ones on it. Comparing with the results of Model A, the maximum stresses decrease for more than 60 % for all monoliths except for those at both banks where the maximum stresses decrease for about 30 %. ...
Context 2
... of the principal stresses on the dam show many differences comparing to the results of Model A. The maximum principal stresses at the end of piers decrease significantly too, by about 80 %. The increase of the stresses on the side wall of the spillway near the end of cushion pool could be due to local topography condition, referring to Fig. 3, but it is not critical to the safety of the ...
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Citations
... Many researchers demonstrated the impact of contraction joints on the earthquake performance of concrete dams utilising the three-dimensional (3D) response. The nonlinear behaviour of concrete gravity (CG) dams was exposed by Wang et al. [26] considering the dynamic contact between dam blocks. Study results demonstrated that the dam's seismic performance depends upon the adhesion degree between the monoliths. ...
One of the major dangers for seismic damage of concrete dams is the propagation of cracks in dam concrete. The present study undertakes a numerical investigation of the seismic damage for Oued Fodda concrete gravity dam, located in the northwest of Algeria, considering the impacts of properties of joints along the dam-foundation rock interface and cross-stream earthquake excitation. Three-dimensional transient analyses for coupled dam-foundation rock system are carried out using Ansys software. The hydrodynamic effect of reservoir fluid is modelled using the added mass approach. The smeared crack approach is utilised to present the seismic damage of dam concrete using the Willam and Warnke failure criterion. The dam-foundation rock interface joints are presented with two ways, adhesive joints and frictional joints. The Drucker–Prager model is considered for dam concrete in nonlinear analyses. Consideration of the study results indicates that the frictional joints model can reduce the seismic response and damage hazard of the dam body to a better extent compared with the adhesive joints model. Furthermore, the application of cross-stream earthquake excitation reveals the significant effect on cracking response of the dam in the two models of joints.
... In three-dimensional (3D) models, Wang et al. (2012) investigated seismic nonlinear performance of CG dams including dam-foundation interaction. An earthquake nonlinear analysis of roller-compacted concrete (RRC) dams was presented by Kartal (2012) considering the friction contact formulation at the dam-foundation-reservoir interface. ...
... These dams are periodically reassessed to evaluate their structural stability while being subjected to anticipated extreme earthquake and flood loads according to the latest state-of-the-art and practice. The presence of shear keys provides some load transfer between monoliths, promoting three-dimensional (3D) interlocking upon sliding initiation and therefore increasing the structural strength that can be mobilised [1][2][3][4][5][6][7]. Ageing concrete dams in need of rehabilitation can therefore benefit from the additional resistance provided by existing shear keys, reducing the costs of potential retrofitting. ...
Shear keys provide interlocking mechanisms along the vertical contraction joints of many concrete gravity dams. The shear key ultimate shear capacity is typically estimated as a function of the friction and cohesion that could be mobilised across a 2D shear plane located at the base of the key when subjected to a normal confinement pressure, P. A two-dimensional response of dam monoliths and shear keys shearing-off at their bases, is assumed. However, evidence of 3D interlocking behaviour between dam monoliths and the possibility of different key failure mechanisms involving interacting axial, P, shear, V, moment, M, and torsion, T, indicates that typical empirical formulations could significantly overestimate the actual shear key capacity under floods and seismic loadings. This paper presents an evaluation of the load–displacement response of shear keys subjected to multiaxial loading via nonlinear finite element analyses. A concrete “Continuous Surface Cap Model” (CSCM), available in the computer program LS-Dyna, is first shown to best capture the experimental shear keys' ultimate and residual shear capacity responses among five constitutive models. The effects of the tensile strength, fracture energy, confinement pressure, friction coefficient, initial opening, and dilation conditions on the load–displacement response of keys are investigated. Failure envelopes considering the key multiaxial shear capacity with confinement pressure, P, moment, M, and torsion, T, are developed. The ratios between moment and shear, M/V, and torsion and shear, T/V, control the failure mechanism. Increasing these ratios significantly reduce the ultimate shear capacity.
... The earthquake response of Outardes 3 concrete gravity (CG) dam was presented by Azmi and Paultre [17] considering the influence of joints using nonlinear joint elements. Wang et al. [18] utilized a 3D finite element model to carry out the nonlinear behavior analysis of CG dams, in which the dynamic contact was taken into consideration between dam blocks. Their results demonstrated that the dam seismic performance depends upon the cohesion degree between the monoliths. ...
The sliding of dam base along dam-foundation rock interface during earthquake excitation can decrease the earthquake response of the dam. The present study reveals a numerical simulation of the seismic failure response for Oued Fodda concrete gravity dam, located in northwest of Algeria, considering base sliding. Nonlinear finite element analyses are performed for Oued Fodda damfoundation rock system. The Smeared crack approach is used to present cracking of dam concrete under the 1980 El Asnam earthquake (M7) using Willam and Warnke failure criterion. The hydrodynamic pressure of the reservoir water is modeled as added mass using the Westergaard approach. The sliding behavior of contractions joints is modeled by surface-surface contact elements that provide the friction contact at dam-foundation interface. Drucker-Prager model is considered for dam concrete in nonlinear analysis. According to numerical analyses, several cracks may appear due to tension particularly at middle upper parts located along the symmetry central axis of the dam in both upstream and downstream faces. Although the dam sliding on its foundation reduces the magnitude of principal tensile stresses in dam body; however, the reduction magnitude is generally not large enough to preclude the cracks propagation in dam body.
... Several factors can affect the dynamic behavior of concrete dams to seismic loads, including the dam-foundation and dam-reservoir interaction. In numerous studies, a reasonable assumption based on massless foundation was used to evade the aforementioned considerations for structures built on rock, such as concrete dams [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. ...
Concrete dams are considered as complex construction systems that play a major role in the context of both economic and strategic utilities. Taking into account reservoir and foundation presence in modeling the dam-reservoir-foundation interaction phenomenon leads to a more realistic evaluation of the total system behavior. The article discusses the dynamic behavior of dam-reservoir-foundation system under seismic loading using Ansys finite element code. Oued Fodda concrete dam, situated at Chlef, in North-West of Algeria, was chosen as a case study. Parametric study was also performed for different ratios between foundation Young's modulus and dam Young's modulus E f /E d (which varies from 0.5 to 4). Added mass approach was used to model the fluid reservoir. The obtained results indicate that when dam Young's modulus and foundation Young's modulus are equal, the foundation soil leads to less displacements in the dam body and decreases the principal stresses as well as shear stresses.
... Burman et al. [8] presented a simplified direct method incorporating the effect of soil-structure interaction (SSI), and carried out a time domain transient analysis of a concrete gravity dam and its foundation in a coupled status. The 3D full dam models with different foundation densities were used to analyze the seismic responses of a concrete gravity dam [9], and the results indicated that the dynamic interaction between the dam and the foundation significantly reduced the responses of the monoliths on the river bed but increased the responses of the monoliths on the steep slopes of both banks. ...
The seismic design and dynamic analysis of high concrete gravity dams is a challenge due to the dams’ high levels of designed seismic intensity, dam height, and water pressure. In this study, the rigid, massless, and viscoelastic artificial boundary foundation models were established to consider the effect of dam–foundation dynamic interaction on the dynamic responses of the dam. Three reservoir water simulation methods, namely, the Westergaard added mass method, and incompressible and compressible potential fluid methods, were used to account for the effect of hydrodynamic pressure on the dynamic characteristics and seismic responses of the dam. The ranges of the truncation boundary of the foundation and reservoir in numerical analysis were further investigated. The research results showed that the viscoelastic artificial boundary foundation was more efficient than the massless foundation in the simulation of the radiation damping effect of the far-field foundation. It was found that a foundation size of 3 times the dam height was the most reasonable range of the truncation boundary of the foundation. The dynamic interaction of the reservoir foundation had a significant influence on the dam stress.
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... To avoid the aforementioned considerations, for structures built on rock such as concrete dams, it is commonly considered that the use of a massless foundation can be a reasonable assumption, which has been implemented in several studies [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. By using this modeling technique, the reflection of seismic waves at the fixed boundary is eliminated and no deconvolution analysis is required [18]. ...
The numerical modeling of the unbounded domain is one of the most challenging issues both for site response and soil-structure interaction analyses. The viscous-type absorbing boundary conditions (ABCs) are commonly used for the modeling of the unbounded domain due to their low computational cost and simplicity. However, in cases, their application can lead to substantial errors. In this paper, a time-domain viscoelastic perfectly matched layer (PML) is implemented for modeling the unbounded domain in the dynamic response evaluation of a concrete gravity dam. The performance of the viscoelastic PML and the viscous ABCs are examined through numerical examples under different types of dynamic excitations including uniform and spatially variable seismic ground motions. The numerical results highlight the excellent performance of the PML approach to model the unbounded domain under all types of excitations. It is also shown that the viscous-type ABCs perform poorly under spatially variable excitations and reflected waves from the structures, as they cannot properly absorb inclined waves. The nonlinear response of a concrete gravity dam subjected to deconvolved seismic excitations at depth resulting from five surface seismic records was then evaluated. The effect of the finite foundation depth on the dam response was also examined by considering a shallow (approximately equal to the height of the dam) and a deep (approximately double the height of the dam) finite foundation length. The results indicate that the PML is capable of maintaining its accuracy even if the size of the computational finite domain is reduced. On the other hand, it was shown that the shallow finite foundations modeled with viscous ABCs substantially underestimate the dam response under uniform excitations, whereas the use of a deep finite foundation model with viscous ABCs can lead to more conservative results. An important conclusion of this study is that the use of foundation models with viscous-type ABCs for the dynamic analysis of dams, and, consequently, other long structures, subjected to spatially variable excitations, should be avoided as it can significantly underestimate the crest displacement and the total damage in the dam.
... The FE model represents the whole structure and a sufficiently wide portion of the ground around it, as indicated in the literature [51]. The geometry of the structure and the shape of the ground are built in a CAD program, based on the original drawings of the dam and the orographic map of the region. ...
The structural control of concrete gravity dams is of primary importance. In this context, numerical models play a fundamental role both to assess the vulnerability of gravity dams and to control their behaviour during normal operativity and after extreme events. In this regard, data monitoring represents an important source of information for numerical model calibrations. This study proposes a novel probabilistic procedure, defined in the Bayesian framework, to calibrate the parameters of finite elements models of dams. To this aim, monitoring data and the results of material tests are used as reference information. The computational burden is reduced by using a new hybrid-predictive model of the dam displacements. An application on an Italian dam shows the feasibility of the proposed procedure.
... Since the use of longer timesteps does not allow the waves (energy) to pass undistorted, the results demonstrate variations in the total energies. To avoid the aforementioned considerations, for structures built on rock such as concrete dams, it is commonly considered that the use of a massless foundation can be a reasonable assumption, which has been implemented in several studies (Akköse and Şimşek 2010;Amina et al. 2015;Ardebili and Mirzabozorg 2012;Arici et al. 2014;Bayraktar et al. 2009Bayraktar et al. , 2010Bayraktar et al. , 2005Clough et al. 1985;Hariri-Ardebili et al. 2018Leger and Boughoufalah 1989;Long et al. 2009;Pan et al. 2014;Sevim et al. 2011;Seyedpoor et al. 2012;Wang et al. 2015Wang et al. , 2012Zhang and Wang 2013). By using this modeling technique, the reflection of seismic waves at the fixed boundary is eliminated and no deconvolution analysis is required (Clough et al. 1985). ...
The numerical modeling of Soil-Structure-Interaction (SSI) is one of the most challenging issues in structural earthquake engineering. Due to the computational cost and complexity of SSI analyses, some simplifications and assumptions have to be made to the real system so that the numerical modeling becomes more tractable. Certainly, such simplifications and assumptions impose uncertainties on the results. This research study examines the limitations of commonly made simplifications and assumptions in the numerical evaluation of structures considering SSI effects, and improves the reliability and accuracy of SSI analyses by developing new analytical and computational approaches. As an example application, a comprehensive model of a dam-foundation system is developed for the seismic response evaluation of concrete gravity dams.
To improve the accuracy of SSI analyses a new deconvolution process, the phase-amplitude modification procedure, is proposed to deconvolve both horizontal and vertical target (design) surface ground motions in multi-layered, equivalent-linear viscoelastic media for use in finite element time-domain structural analyses. It is shown that the approach can accurately estimate the seismic excitations at depth of soil profiles. In addition, a viscoelastic Perfectly Matched Layer (PML) formulation with Rayleigh-type damping is developed and implemented in ABAQUS/Standard by merging it with a User-Defined Element (UEL) subroutine in Fortran90. The performance of the viscoelastic PML vs. the commonly-used viscous Absorbing Boundary Conditions (ABCs) is examined through numerical examples under different types of dynamic excitations including uniform and spatially variable seismic ground motions. The numerical results highlight the excellent performance of the PML approach to model the unbounded domain under all types of excitations. The proposed numerical models are implemented in the finite element seismic evaluation of a concrete gravity dams, and the results are compared to the simplified dam-foundation models that are being used widely by both academicians and practitioners. It is shown that the use of the massless foundation model as well as the massed foundation model with viscous-type ABCs can lead to substantial errors in the dynamic response of concrete dams. This is the first study ever that rigorously evaluates the effect of foundation modeling on the dam response under uniform and spatially variable excitations.
