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Victor E. Saouma - One of the best experts on this subject based on the ideXlab platform.
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probabilistic seismic demand model and optimal intensity measure for concrete Dams
Structural Safety, 2016Co-Authors: Mohammad Amin Haririardebili, Victor E. SaoumaAbstract:Abstract This paper addresses the probabilistic seismic demand model (PSDM) which is the relationship between the intensity measure (IM) (such as spectral acceleration) and the engineering demand parameter (EDP) (such as displacement and crack ratio – ratio of crack length to total crack path). It expresses the probability that a system experiences a certain level of demand for a given IM level. Formulation is for a concrete Gravity Dam. First, IMs are categorized and the criteria for the selection of an optimal one presented. Then, cloud analysis is performed where the structure is subjected to a large set of un-scaled ground motions and the maximum responses are extracted for each one and plotted as a cloud of results. This methodology is applied to Pine Flat Gravity Dam. Model is first presented followed by results and conclusions. When the results of the cloud analysis are aggregated, then one can plot the seismic fragility curve which is the probability of EDP exceedance in terms of the IM parameter.
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probabilistic seismic demand model and optimal intensity measure for concrete Dams
Structural Safety, 2016Co-Authors: Mohammad Amin Haririardebili, Victor E. SaoumaAbstract:Abstract This paper addresses the probabilistic seismic demand model (PSDM) which is the relationship between the intensity measure (IM) (such as spectral acceleration) and the engineering demand parameter (EDP) (such as displacement and crack ratio – ratio of crack length to total crack path). It expresses the probability that a system experiences a certain level of demand for a given IM level. Formulation is for a concrete Gravity Dam. First, IMs are categorized and the criteria for the selection of an optimal one presented. Then, cloud analysis is performed where the structure is subjected to a large set of un-scaled ground motions and the maximum responses are extracted for each one and plotted as a cloud of results. This methodology is applied to Pine Flat Gravity Dam. Model is first presented followed by results and conclusions. When the results of the cloud analysis are aggregated, then one can plot the seismic fragility curve which is the probability of EDP exceedance in terms of the IM parameter.
Mohammad Amin Haririardebili - One of the best experts on this subject based on the ideXlab platform.
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analytical failure probability model for generic Gravity Dam classes
Proceedings of the Institution of Mechanical Engineers Part O: Journal of Risk and Reliability, 2017Co-Authors: Mohammad Amin HaririardebiliAbstract:Risk analysis of concrete Dams and quantification of the failure probability are important tasks in Dam safety assessment. The conditional probability of demand and capacity is usually estimated by numerical simulation and Monte Carlo technique. However, the estimated failure probability (or the reliability index) is Dam-dependent which makes its application limited to some case studies. This article proposes an analytical failure model for generic Gravity Dam classes which is optimized based on large number of nonlinear finite element analyses. A hybrid parametric–probabilistic–statistical approach is used to estimate the failure probability as a function of Dam size, material distributional models and external hydrological hazard. The proposed model can be used for preliminary design and evaluation of two-dimensional Gravity Dam models.
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fem based parametric analysis of a typical Gravity Dam considering input excitation mechanism
Soil Dynamics and Earthquake Engineering, 2016Co-Authors: Mohammad Amin Haririardebili, S M Seyedkolbadi, M R KianoushAbstract:Abstract This paper studies computer-aided parametric analysis on the finite element model of a typical concrete Gravity Dam. The coupled Dam–foundation–reservoir system is modeled based on Lagrangian–Eulerian approach. The nonlinearity in the Dam is originated from a developed rotating smeared crack model. Different types of input ground motions are used for excitation of the structural system, i.e. near-fault vs. far-field, real vs. artificial, and uniform vs. non-uniform. The spatial varying ground motions and endurance time acceleration functions are generated based on a non-stationary random process. Finally, results are presented in terms of displacement and crack propagation. Relative importance of different parameters is compared and an optimum numerical model is suggested for potential applications.
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probabilistic seismic demand model and optimal intensity measure for concrete Dams
Structural Safety, 2016Co-Authors: Mohammad Amin Haririardebili, Victor E. SaoumaAbstract:Abstract This paper addresses the probabilistic seismic demand model (PSDM) which is the relationship between the intensity measure (IM) (such as spectral acceleration) and the engineering demand parameter (EDP) (such as displacement and crack ratio – ratio of crack length to total crack path). It expresses the probability that a system experiences a certain level of demand for a given IM level. Formulation is for a concrete Gravity Dam. First, IMs are categorized and the criteria for the selection of an optimal one presented. Then, cloud analysis is performed where the structure is subjected to a large set of un-scaled ground motions and the maximum responses are extracted for each one and plotted as a cloud of results. This methodology is applied to Pine Flat Gravity Dam. Model is first presented followed by results and conclusions. When the results of the cloud analysis are aggregated, then one can plot the seismic fragility curve which is the probability of EDP exceedance in terms of the IM parameter.
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probabilistic seismic demand model and optimal intensity measure for concrete Dams
Structural Safety, 2016Co-Authors: Mohammad Amin Haririardebili, Victor E. SaoumaAbstract:Abstract This paper addresses the probabilistic seismic demand model (PSDM) which is the relationship between the intensity measure (IM) (such as spectral acceleration) and the engineering demand parameter (EDP) (such as displacement and crack ratio – ratio of crack length to total crack path). It expresses the probability that a system experiences a certain level of demand for a given IM level. Formulation is for a concrete Gravity Dam. First, IMs are categorized and the criteria for the selection of an optimal one presented. Then, cloud analysis is performed where the structure is subjected to a large set of un-scaled ground motions and the maximum responses are extracted for each one and plotted as a cloud of results. This methodology is applied to Pine Flat Gravity Dam. Model is first presented followed by results and conclusions. When the results of the cloud analysis are aggregated, then one can plot the seismic fragility curve which is the probability of EDP exceedance in terms of the IM parameter.
Gaohui Wang - One of the best experts on this subject based on the ideXlab platform.
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deterministic 3d seismic Damage analysis of guandi concrete Gravity Dam a case study
Engineering Structures, 2017Co-Authors: Gaohui Wang, Yongxiang Wang, Chao WangAbstract:Abstract This paper presents an original investigation of the seismic cracking behavior of Guandi concrete Gravity Dam, which is located in the highly seismic zone of China. For this purpose, three dimensional nonlinear finite element analyses are carried out for the Guandi Dam-reservoir-foundation system, with the effects of contraction joints and cross-stream seismic excitation considered. The Concrete Damaged Plasticity (CDP) model is utilized to model concrete cracking under seismic loading. The opening/closing and sliding behaviors of contraction joints during earthquake events are modeled using two different surface-to-surface contact models (soft and hard pressure-clearance relationships), which aims to quantify the effect of grouting materials between the joint surfaces. The dynamic interaction between the impounded water and the Dam-foundation system is explicitly taken into account by modeling the reservoir water with three dimensional fluid finite elements in the Lagrangian formulation. Several case studies are examined and the results reveal the significant influence of contraction joints and cross-stream ground motions on the dynamic response and Damage-cracking risk of the Guandi concrete Gravity Dam.
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Damage demand assessment of mainshock Damaged concrete Gravity Dams subjected to aftershocks
Soil Dynamics and Earthquake Engineering, 2017Co-Authors: Gaohui Wang, Yongxiang Wang, Wenbo Lu, Wei Zhou, Ming ChenAbstract:Abstract In China, the current seismic codes specify a single earthquake event as the design seismic load for concrete Gravity Dams. However, a large mainshock usually triggers numerous aftershocks in a short period. This paper assesses the effects of aftershocks on concrete Gravity Dam–reservoir–foundation systems and provides a quantitative description of the Damage demands prior to and following the aftershocks. For this purpose, a set of 20 as-recorded mainshock–aftershock seismic sequences is considered in this study. The correlation between the ground motion characteristics of the as-recorded mainshocks and those of the aftershocks is examined. In order to identify the influence of the ground motion characteristics of aftershocks on the Damage demands of the mainshock-Damaged Dams, the nonlinear behavior of the concrete Gravity Dams that are subjected to single seismic events and typical as-recorded seismic sequences is compared in terms of the structural Damage, displacement response, and Damage dissipated energy. A series of nonlinear dynamic analyses is performed to quantify the influence of aftershocks, which are selected by using different methods, on the Damage demands of concrete Gravity Dam–reservoir–foundation systems in terms of the local and global Damage indices. The results show that the aftershocks lead to an increase in the Damage demands of the Dam at the end of the seismic sequence when the concrete Gravity Dam is already Damaged during the first individual seismic event and has not been repaired. In addition, the results also reveal that the repeated seismic sequences tend to underestimate the level of Damage demands.
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xfem based seismic potential failure mode analysis of concrete Gravity Dam water foundation systems through incremental dynamic analysis
Engineering Structures, 2015Co-Authors: Gaohui Wang, Ming Chen, Yongxiang Wang, Chuangbing Zhou, Peng YanAbstract:Abstract As revealed by the structural Damage of concrete Dams (e.g. Hsinfengkiang, Koyna, Sefid-Rud) arising in recent earthquakes, cracking Damage would probably occur inside concrete Dams when subjected to strong ground motions. This phenomenon is caused by the low tensile resistance of concrete. Research on the cracking Damage process and failure modes of concrete Gravity Dams subjected to strong earthquakes is crucial to a reasonable assessment of the seismic safety of Dams. In this paper, the extended finite element method (XFEM) is presented to describe the crack propagation within concrete Gravity Dams subjected to earthquake loads. Moreover, the interaction between the impounded water and the Dam–foundation system is explicitly taken into account by modeling the reservoir water with two-dimensional fluid finite elements in the Lagrangian formulation. In order to validate the proposed algorithm, seismic crack analysis is performed to investigate the failure modes of the Koyna Dam–reservoir–foundation system under the 1967 Koyna earthquake. It shows that the cracking Damage profile obtained from the proposed XFEM framework agrees well with that reported in the literature. With the validated algorithm, we further apply it to study the potential failure modes of the Guandi concrete Gravity Dam. Seismic cracking response of concrete Gravity Dams considering the effects of the Dam–reservoir–foundation interaction is obtained through the incremental dynamic analysis (IDA) based XFEM. 40 as-recorded accelerograms with each scaled to 8 increasing intensity levels are selected in this study. Based on the 320 numerical simulation results, typical failure processes and five potential failure modes of concrete Gravity Dams under the selected database of strong earthquake ground motions are presented.
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methodology for estimating probability of dynamical system s failure for concrete Gravity Dam
Journal of Central South University, 2014Co-Authors: Chao Wang, Sherong Zhang, Bo Sun, Gaohui WangAbstract:Methodology for the reliability analysis of hydraulic Gravity Dam is the key technology in current hydropower construction. Reliability analysis for the dynamical Dam safety should be divided into two phases: failure mode identification and the calculation of the failure probability. Both of them are studied based on the mathematical statistics and structure reliability theory considering two kinds of uncertainty characters (earthquake variability and material randomness). Firstly, failure mode identification method is established based on the dynamical limit state system and verified through example of Koyna Dam so that the statistical law of progressive failure process in Dam body are revealed; Secondly, for the calculation of the failure probability, mathematical model and formula are established according to the characteristics of Gravity Dam, which include three levels, that is element failure, path failure and system failure. A case study is presented to show the practical application of theoretical method and results of these methods.
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seismic cracking analysis of concrete Gravity Dams with initial cracks using the extended finite element method
Engineering Structures, 2013Co-Authors: Sherong Zhang, Gaohui Wang, Xiangrong YuAbstract:Abstract The seismic crack propagation of concrete Gravity Dams with initial cracks at the upstream and downstream faces has rarely been studied during strong earthquakes. In this paper, a numerical scheme based on the extended finite element method (XFEM), which has been widely used for the analysis of crack growth, is presented to deal with the numerical prediction of crack propagation in concrete Gravity Dams. The validity of the algorithm is discussed by comparing results obtained from the proposed XFEM with those reported in the literature. For this purpose, the cracking process and final crack profile of Koyna Dam during the 1967 Koyna earthquake are simulated numerically by employing the XFEM. The computed distribution of cracking Damage is consistent with the actual condition and the results of model test and available methods in literature, which verifies the validity of the calculation model. Subsequently, the Koyna Dam with single and multiple initial cracks is also analyzed using the proposed approach, which is investigated to evaluate the seismic crack propagation of the concrete Gravity Dam with initial cracks. The effects of initial cracks on the crack propagation and seismic response of the concrete Gravity Dam are discussed.
Alemdar Bayraktar - One of the best experts on this subject based on the ideXlab platform.
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The effect of reservoir length on seismic performance of Gravity Dams to near- and far-fault ground motions
Natural Hazards, 2010Co-Authors: Alemdar Bayraktar, Temel Türker, Mehmet Akköse, Şevket AteşAbstract:In this article, the effect of reservoir length on seismic performance of Gravity Dams to near- and far-fault ground motions is investigated. For this purpose, four finite element models of Dam–reservoir–foundation interaction system are prepared by using the Lagrangian approach. In these models, the reservoir length varies from H to 4 H ( H : the height of Dam). The Folsom Gravity Dam is selected as a numerical application. Two different ground motion records of 1989 Loma Prieta earthquake are used in the analyses. One of ground motions is recorded in near fault; the other is recorded in far fault. Also, the two records have the same peak ground acceleration. The study mainly consists of three parts to assess the effects of reservoir length on the seismic performance of the concrete Gravity Dam. In the first part, the linear time-history analyses of the four finite element models prepared for the Folsom Gravity Dam are performed. In the second part, the seismic performance of the Dam is evaluated according to demand–capacity ratio and cumulative inelastic duration. Finally, the nonlinear time-history analyses of the finite element models of the Dam are carried out by using Drucker–Prager yield criteria for Dam concrete. It is seen from the analyses results that the seismic behavior of the concrete Gravity Dams is considerably affected from the length of the reservoir. The reservoir length of 3 H is adequate for concrete Gravity Dams. The selection of ground motion is on of the important parts of seismic evaluation of Gravity Dams. Also, the frequency characteristics of the ground motion having the same peak ground acceleration affect the seismic performance of the Dam. The near-fault ground motions are generally creates more stress on the Dam body than far-fault ground motions. The used performance approach provides a systematic methodology for assessment of the seismic performance and necessity of nonlinear analyses for Dam systems.
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EARTHQUAKE ANALYSIS OF Gravity Dam-RESERVOIR SYSTEMS USING THE EULERIAN AND LAGRANGIAN APPROACHES
Computers & Structures, 1996Co-Authors: Y. Calayir, A.a. Dumanoglu, Alemdar BayraktarAbstract:In this study, the two-dimensional earthquake analysis of a Gravity Dam-reservoir system using both the Eulerian and Lagrangian approaches is performed. To this aim, the effects of the variation of fluid compressibility on the modal behavior were first investigated. Then, the earthquake response of a Dam-reservoir system is investigated using the Lagrangian approach. Parametric studies are conducted on increasing the value of fluid bulk modulus. The results obtained for different values of the bulk modulus are also compared with the Eulerian solutions based on incompressible fluid assumption.
Damodar Maity - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation on nonlinear dynamic response of concrete Gravity Dam reservoir system
Engineering Structures, 2014Co-Authors: Subrata Mridha, Damodar MaityAbstract:Abstract The nonlinear response of concrete Gravity Dam-reservoir system has been investigated by conducting experiments on small scale model of Koyna Dam on a horizontal shake table using sinusoidal chirp motions. Two dimensional models of non-overflow section of Koyna Dam have been prepared in the laboratory with a scale ratio of 1:150. To satisfy the laws of similitude, an appropriate ratio of cement, sand, bentonite and water has been mixed to find the target properties of model Dam. Dam models have been casted over a wooden base plate using a wooden mould. After setting and drying process the wooden mould has been removed and each Dam model has been assembled with a reservoir model after placing them over a horizontal shake table. The interaction between Dam and reservoir model has been made in such a manner, so that it can transmit the hydro dynamic force of reservoir water to the Dam model without allowing any seepage of water across it. Experiments have been performed on the Dam-reservoir system with empty and full reservoir water by applying horizontal sinusoidal chirp excitations to the shake table to observe the basic behaviour, crack formation, crack opening, sliding along crack planes and stability after crack formation of the Dam model. The numerical analysis of the system has been carried out using ABAQUS 6.10 considering Damage plasticity model. The effect of foundation has been neglected assuming a rigid Dam foundation as the Dam is placed on a rigid plate. The eigen frequencies of the Dam model have been calculated and compared with experimental values to calibrate the analysis model. The crack propagation due to tensile Damages is computed and the results are compared with the experimental results. The outcome of the response results shows the correctness of the developed experimental model of Dam-reservoir system.
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coupled Gravity Dam foundation analysis using a simplified direct method of soil structure interaction
Soil Dynamics and Earthquake Engineering, 2012Co-Authors: A Burman, Parsuram Nayak, P Agrawal, Damodar MaityAbstract:A time domain transient analysis of a concrete Gravity Dam and its foundation has been carried out in a coupled manner using finite element technique and the effect of Soil–Structure Interaction (SSI) has been incorporated using a simplified direct method. A two dimensional plane strain Dam–foundation model has been used for the time history analysis to compute the stresses and displacements against earthquake loading considering the effect of soil–structure interaction. An effective boundary condition has been implemented by attaching dashpots to the vertical boundaries. The material Damping effects have also been considered and the Dam and foundation have both been modeled as linear, elastic materials. To achieve a greater degree of accuracy, the displacements and stresses calculated in the free-field analysis have also been added to those developed in the complete Dam–foundation analysis. The proposed algorithm has been simulated for the case of two published problems and in both the cases the results have been found to be in close agreement. The proposed technique is quite simple and easy to implement in the computer code. The outcomes of the results show the efficacy of the developed method.
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iterative analysis of concrete Gravity Dam nonlinear foundation interaction
International journal of engineering science and technology, 2010Co-Authors: A Burman, Damodar Maity, S SreedeepAbstract:This paper deals with finite element analysis of the soil–structure systems considering the coupled effect of elastic structure and materially nonlinear soil. The equations of motion of both soil and structure have been expressed in terms of displacement variable. The structure and the soil domain are treated as two separate systems. The solution of the coupled system is accomplished by solving the two systems separately and then considering the interaction effects at the soil–structure interface enforced by a developed iterative scheme. Emphasis has been laid on the study of material nonlinearity of the foundation material in the interaction analysis. The results show the pronounced effects of displacements and stresses for the structure when the foundation is assumed to be composed of nonlinear materials. A widely popular model called Duncan-Chang model has been used for representing nonlinear material behavior of soil/rock. In order to represent the semi-infinite nature of the foundation domain, the Lysmer-Kuhlemeyer boundary condition consisting of viscous dashpots have been used. Studies show the accuracy of the proposed algorithm, while comparing with the results reported in the literature. Keywords: Concrete Gravity Dam; Dam-foundation interaction; iterative algorithm; Duncan-Chang model; viscous dashpots.
