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Gregory L. Fenves - One of the best experts on this subject based on the ideXlab platform.
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earthquake response of concrete Gravity Dams including base sliding
Journal of Structural Engineering-asce, 1995Co-Authors: Juan W Chavez, Gregory L. FenvesAbstract:The stability of a concrete Gravity dam against sliding along the interface between the dam base and the foundation rock must be assured in a seismic safety evaluation. The hybrid frequency–time domain procedure is used to compute the earthquake response of Gravity Dams, including base sliding. The procedure accounts for the nonlinear base sliding of the dam and the frequency-dependent response of the impounded water and the flexible foundation rock. A parameter study of typical Gravity Dams shows how the earthquake-induced sliding is affected by the characteristics of the ground motion and dam system. Based on the results of the study, it is necessary to include the effects of dam–foundation rock interaction to obtain realistic estimates of the base sliding displacement for a dam. The sliding displacement is sensitive to the value of the coefficient of friction for the interface zone, especially for moderate to tall Dams. Water compressibility also affects the base sliding displacement. Although a dam re...
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earthquake analysis of concrete Gravity Dams including base sliding
Earthquake Engineering & Structural Dynamics, 1995Co-Authors: Juan W Chavez, Gregory L. FenvesAbstract: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.
Juan W Chavez - One of the best experts on this subject based on the ideXlab platform.
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earthquake response of concrete Gravity Dams including base sliding
Journal of Structural Engineering-asce, 1995Co-Authors: Juan W Chavez, Gregory L. FenvesAbstract:The stability of a concrete Gravity dam against sliding along the interface between the dam base and the foundation rock must be assured in a seismic safety evaluation. The hybrid frequency–time domain procedure is used to compute the earthquake response of Gravity Dams, including base sliding. The procedure accounts for the nonlinear base sliding of the dam and the frequency-dependent response of the impounded water and the flexible foundation rock. A parameter study of typical Gravity Dams shows how the earthquake-induced sliding is affected by the characteristics of the ground motion and dam system. Based on the results of the study, it is necessary to include the effects of dam–foundation rock interaction to obtain realistic estimates of the base sliding displacement for a dam. The sliding displacement is sensitive to the value of the coefficient of friction for the interface zone, especially for moderate to tall Dams. Water compressibility also affects the base sliding displacement. Although a dam re...
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earthquake analysis of concrete Gravity Dams including base sliding
Earthquake Engineering & Structural Dynamics, 1995Co-Authors: Juan W Chavez, Gregory L. FenvesAbstract: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.
Anil K Chopra - One of the best experts on this subject based on the ideXlab platform.
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response spectrum analysis of concrete Gravity Dams including dam water foundation interaction
Journal of Structural Engineering-asce, 2015Co-Authors: Arnkjell Lokke, Anil K ChopraAbstract:AbstractA response spectrum analysis (RSA) procedure, which estimates the peak response directly from the earthquake design spectrum, is available for the preliminary phase of design and safety evaluation of concrete Gravity Dams. This analysis procedure includes the effects of dam-water foundation interaction, known to be important in the earthquake response of Dams. This paper presents a comprehensive evaluation of the accuracy of this RSA procedure by comparing its results with those obtained from response history analysis (RHA) of the dam modeled as a finite-element system, including dam-water-foundation interaction. The earthquake response of an actual dam to an ensemble of 58 ground motions, selected and scaled to be consistent with a target spectrum determined from a probabilistic seismic hazard analysis for the dam site, was determined by the RHA procedure. The median of the peak responses of the dam to 58 ground motions provided the benchmark result. The peak response was also estimated by the RS...
Bruce R Ellingwood - One of the best experts on this subject based on the ideXlab platform.
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seismic fragility assessment of concrete Gravity Dams
Earthquake Engineering & Structural Dynamics, 2003Co-Authors: Paulos B Tekie, Bruce R EllingwoodAbstract:Many concrete Gravity Dams have been in service for over 50 years, and over this period important advances in the methodologies for evaluation of natural phenomena hazards have caused the design-basis events for these Dams to be revised upwards. Older existing Dams may fail to meet revised safety criteria and structural rehabilitation to meet such criteria may be costly and difficult. Fragility assessment provides a tool for rational safety evaluation of existing facilities and decision-making by using a probabilistic framework to model sources of uncertainty that may impact dam performance. This paper presents a methodology for developing fragilities of concrete Gravity Dams to assess their performance against seismic hazards. The methodology is illustrated using the Bluestone Dam on the New River in West Virginia, which was designed in the late 1930s. The seismic fragility assessment indicated that sliding along the dam–foundation interface is likely if the dam were to be subjected to an earthquake with a magnitude of the maximum credible earthquake (MCE) specified by the U.S. Army Corps of Engineers. Moreover, there will likely be tensile cracking at the neck of the dam at this level of seismic excitation. However, loss of control of the reservoir is unlikely. Copyright © 2003 John Wiley & Sons, Ltd.
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seismic fragility assessment of concrete Gravity Dams
Earthquake Engineering & Structural Dynamics, 2003Co-Authors: Paulos B Tekie, Bruce R EllingwoodAbstract:Many concrete Gravity Dams have been in service for over 50 years, and over this period important advances in the methodologies for evaluation of natural phenomena hazards have caused the design-basis events for these Dams to be revised upwards. Older existing Dams may fail to meet revised safety criteria and structural rehabilitation to meet such criteria may be costly and difficult. Fragility assessment provides a tool for rational safety evaluation of existing facilities and decision-making by using a probabilistic framework to model sources of uncertainty that may impact dam performance. This paper presents a methodology for developing fragilities of concrete Gravity Dams to assess their performance against seismic hazards. The methodology is illustrated using the Bluestone Dam on the New River in West Virginia, which was designed in the late 1930s. The seismic fragility assessment indicated that sliding along the dam–foundation interface is likely if the dam were to be subjected to an earthquake with a magnitude of the maximum credible earthquake (MCE) specified by the U.S. Army Corps of Engineers. Moreover, there will likely be tensile cracking at the neck of the dam at this level of seismic excitation. However, loss of control of the reservoir is unlikely. Copyright © 2003 John Wiley & Sons, Ltd.
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fragility analysis of concrete Gravity Dams
Journal of Infrastructure Systems, 2001Co-Authors: Paulos B Tekie, Bruce R EllingwoodAbstract:Concrete Gravity Dams are an important part of the nation's infrastructure. Many Dams have been in service for decades. During the service life of a dam, operating conditions and natural environmental factors may have led to some deterioration in its structural integrity, mechanical equipment, and foundation. Moreover, advances in the methodologies by which design-basis events for natural phenomena hazards are identified have caused these events to be revised upward, in some cases significantly. An increasing number of existing Dams fail to meet the more recent performance criteria. A fragility model of a dam provides a tool for rational safety assessment and decision making by using a probabilistic framework to manage the various sources of uncertainty that affect dam performance. In this paper, basic fragility concepts are presented, and databases required to support the fragility assessment are identified. The method is illustrated using a concrete monolith from the Bluestone Dam in West Virginia, designed in the late 1930s. Traditional design practices have been sufficiently conservative that the probability of dam failure under a probable maximum flood 11 m (36 ft) higher than the original design-basis flood remains small.
S Valliappan - One of the best experts on this subject based on the ideXlab platform.
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seismic cracking of concrete Gravity Dams by plastic damage model using different damping mechanisms
Finite Elements in Analysis and Design, 2013Co-Authors: Omid Omidi, S Valliappan, Vahid LotfiAbstract:Utilizing two different damping mechanisms, seismic cracking response of concrete Gravity Dams is examined by a plastic-damage model implemented in three-dimensional space. The material constitutive law employed herein is based on the one proposed by Lee and Fenves for the 2-D plane stress case. This plastic-damage model basically intended for cyclic or dynamic loading was founded on the combination of non-associated multi-hardening plasticity and isotropic damage theory to simulate the irreversible damages occurring in fracturing process of concrete. In this study, considering the HHT scheme as an implicit operator, the time integration procedure to iteratively solve the governing nonlinear equations is presented. Further, seismic fracture responses of Gravity Dams due to constant and damage-dependent damping mechanisms are compared. In order to assess the validity of the proposed model, several simple examples are solved and their results are presented first. Subsequently, Koyna Gravity dam, which is a benchmark problem for the seismic fracture researches, is analyzed. It is concluded that employing the damage-dependent damping mechanism leads to more extensive damages and also predicts more reliable crack patterns in comparison with the constant damping mechanism in seismic analysis of concrete Dams. Furthermore, including dam-water interaction intensifies the existing differences between the results of the two damping mechanisms.
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non linear seismic behaviour of concrete Gravity Dams using coupled finite element boundary element technique
International Journal for Numerical Methods in Engineering, 1999Co-Authors: M Yazdchi, N Khalili, S ValliappanAbstract:In this paper, the seismic response of concrete Gravity Dams is presented using the concept of Continuum Damage Mechanics (CDM) and adopting the hybrid Finite Element–Boundary Element technique (FE–BE). The finite element method is used for discretization of the near field and the boundary element method is employed to model the semi-infinite far field. Because of the non-linear nature of the discretizied equations of motion modified Newton–Raphson approach has been used at each time step to linearize them. Damage evolution based on tensile principal strain using mesh-dependent hardening modulus technique is adopted to ensure the mesh objectivity and to calculate the accumulated damage. The methodology employed is shown to be computationally efficient and consistent in its treatment of both damage growth and damage propagation in Gravity Dams. Other important features considered in the analysis are: (1) realistic damage modelling for concrete that allows isotropic as well as anisotropic damage state and exhibits stiffness recovery upon load reversals. (2) softening initiation and strain softening criteria for concrete, and (3) proper modelling of semi-infinite foundation using FE–BE method that allows to consider dam–foundation interaction analysis. As an application of the proposed formulation a Gravity dam has been analysed and the results are compared with different foundation stiffnesses. The results of the analysis indicate the importance of including rock foundation in the seismic analysis of Dams. Copyright © 1999 John Wiley & Sons, Ltd.
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earthquake analysis of Gravity Dams based on damage mechanics concept
International Journal for Numerical and Analytical Methods in Geomechanics, 1996Co-Authors: S Valliappan, M Yazdchi, N KhaliliAbstract:In this paper, the seismic response analysis of concrete Gravity Dams is presented using the concept of Continuum Damage Mechanics. The analysis is performed using the finite element technique and a proper material degradation/damage model. The damage criterion used here is a second order tensor model based on elastic-brittle characterization and on a power function of the principal tensile stress. The methodology employed is shown to be computationally efficient and consistent in its treatment of both damage growth and propagation. Other important features considered in the analysis are: (1) dam-foundation interaction (2) appropriate modelling of joined rock mass using continuum damage mechanics, and (3) proper modelling of unbounded domain of foundation rock. The infinite media representation of the foundation material has been achieved by using doubly asymptotic approximation. The results of the analysis indicate that the seismic response of a damaged concrete dam could be significantly different from that of an undamaged one. In particular, the analysis shows that during a seismic event, the microstructure of a damaged zone can significantly change due to growth and propagation of microcracks.
