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An experimental study of a small-scale model of a concrete gravity dam was conducted. Tests were carried out to simulate the hydrostatic, hydrodynamic, and seismic loads. The dynamic loads were estimated using the simplified metho...
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An experimental study of a small-scale model of a concrete gravity dam was conducted. Tests were carried out to simulate the hydrostatic, hydrodynamic, and seismic loads. The dynamic loads were estimated using the simplified method of analysis in concrete gravity dams. A loading mechanism with two actuators was designed to apply four concentrated loads at the upstream face of the dam model. The static load that represents the hydrostatic pressure was kept constant. The dynamic load was applied cyclically by an actuator to represent the dynamic effects of the earthquake loading. An existing concrete gravity dam monolith was modeled. The material properties of the model were maintained the same as those of the prototype. The gravity load effect of the dam was accounted for analytically. Results of the experiments show that it is possible to simulate the hydrodynamic load on a dam model using a finite number of concentrated mechanical loads. Measured strains in the dam model were found to be similar to the strains in the prototype predicted using available finite element analysis techniques. [References: 20]
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In this paper an intrinsic arch, which will create an arch action in straight concrete dams, is revealed from the results of a back-analysis on a 4m thick concrete core with straight axis in a rockfill cofferdam. The concrete core...
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In this paper an intrinsic arch, which will create an arch action in straight concrete dams, is revealed from the results of a back-analysis on a 4m thick concrete core with straight axis in a rockfill cofferdam. The concrete core has stood for two years functioning as the cofferdam to withstand upstream water and sediment pressure after all the material supporting the core was washed away during overtopping. The arch action existing in straight concrete dams challenges the traditional two-dimensional cantilever theory (gravity method) for the design of gravity dams. Results of the three-dimensional finite element back-analysis are compared with those observed on site, and agreement of the results confirms the arch effect. The conditions for forming the arch action in straight concrete dams are discussed, on the basis of which new design and construction philosophy is proposed, considering the arch action for straight concrete dams. This may result in project cost savings and/or increased dam safety.
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A new method using neural networks for the transformation of results from dam models to prototypes has been proposed and validated through application to Koyna and Pine-Flat Dams, which have also been investigated by other researc...
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A new method using neural networks for the transformation of results from dam models to prototypes has been proposed and validated through application to Koyna and Pine-Flat Dams, which have also been investigated by other researchers. The neural network has been called the neurotransformer. The common method for building a suitable experimental model for a dam to be tested on a shaking table is linear dimensional analysis or simply linear scaling (LS). However, because LS is theoretically applicable to linear systems, it generally provides imprecise results of transformation for extreme loading when the model or the prototype experiences noticeable nonlinearity. In this paper, it is shown through numerical simulation of the dynamic behaviour of Koyna Dam and its 1/50 model under strong earthquakes, which cause nonlinear behavior in both the dam and its model, that transformation by neural networks is considerably more precise than LS. To show the method can also be applied to other dams, the same procedure was successfully applied to Pine-Flat Dam; again, the neurotransformer outperformed the LS.
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Large dams are a part of the infrastructure of any society, and a huge amount of resources are consumed to build them. Among the various types of dams, the optimum design of concrete gravity dams requires special attention because...
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Large dams are a part of the infrastructure of any society, and a huge amount of resources are consumed to build them. Among the various types of dams, the optimum design of concrete gravity dams requires special attention because these types of dams require a huge amount of concrete for their construction. On the other hand, concrete gravity dams are among the structures whose design, regarding the acting forces, geometric parameters, and resistance and stability criteria, has some complexities. In the present study, an optimization methodology is proposed based on Sequential Quadratic Programming (SQP), and a computer program is developed to perform optimization of concrete gravity dams. The optimum results for 45 concrete gravity dams are studied and regression analyses are performed to obtain some explicit formulas for optimization of the gravity dams. The optimization of concrete gravity dams can be provided easily using the developed formulas, without the need to perform any more optimization process.
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A 204 m high solid concrete gravity dam isproposed across the River Yamuna in Garhwal Himalaya, India. Itwill be located on dolerite rocks which have been intruded intothe slates of Chandpur Formation. The present study includes t...
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A 204 m high solid concrete gravity dam isproposed across the River Yamuna in Garhwal Himalaya, India. Itwill be located on dolerite rocks which have been intruded intothe slates of Chandpur Formation. The present study includes theevaluation of the dam foundation by means of drifts, drill holes,water pressure tests and abutment slope stability studies. Thewater pressure test indicate the necessity of providing a groutcurtain below the dam foundation. The analysis of the damabutments for stability using the Limit equilibrium methodindicates that the right abutment slope is kinematically unstablefor plane failure mode. The plane failure analysis of the rightabutment slope was carried out by modifying the Hoek and Bray(1981, Rock Slope Engineering, 3rd, ed., Institute of Mining andMetallurgy, London) technique of plane failure analysis. Theanalysis reveals that right abutment slope may become unstableduring the stripping operation. Based upon the analysis a safe cutslope design for the abutments have been suggested. Subsurfaceexploration by means of cross drift and drill holes have indicateda sheared contact of slate and dolerite in the foundation area. Toavoid the settlement of the dam along this shear zoneprecautionary measures are suggested.
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Rockfill buttressing resting on the downstream face of masonry or concrete gravity dam is often considered as a strengthening method to improve the stability of existing dam for hydrostatic and seismic loads. Simplified methods fo...
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Rockfill buttressing resting on the downstream face of masonry or concrete gravity dam is often considered as a strengthening method to improve the stability of existing dam for hydrostatic and seismic loads. Simplified methods for seismic stability analysis of composite concrete-rockfill dams are discussed. Numerical analyses are performed using a nonlinear rockfill model and nonlinear dam-rockfill interface behavior to investigate the effects of backfill on dynamic response of composite dams. A typical 35m concrete gravity dam, strengthened by rockfill buttressing is considered. The results of analyses confirm that backfill can improve the seismic stability of gravity dams by exerting pressure on the dam in opposition to hydrostatic loads. According to numerical analyses results, the backfill pressures vary during earthquake base excitations and the inertia forces of the backfill are the main source for those variations. It is also shown that significant passive (or active) pressure cannot develop in composite dams with a finite backfill width. A simplified model is also proposed for dynamic analysis of composite dam by replacing the backfill with by a series of vertical cantilever shear beams connected to each other and to the dam by flexible links.
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Non-linear seismic response of a concrete gravity dam is investigated to determine the effects of construction joints. A non-linear finite element model is presented to capture seismic behaviour of the horizontal construction join...
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Non-linear seismic response of a concrete gravity dam is investigated to determine the effects of construction joints. A non-linear finite element model is presented to capture seismic behaviour of the horizontal construction joints. The non-linear seismic analysis is conducted under the effect of the horizontal construction joints as well as dam-reservoir interaction. The dam-reservoir interaction effects were considered using staggered method. The analysis is applied to the case of a gravity dam with infinite reservoir under the horizontal earthquake ground motion. It was found that the horizontal construction joint could change the seismic response of the dam.
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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...
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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 between dam and foundation affects the dam response as well, including reflection, diffraction and radiation of seismic waves. In the paper, a three-dimensional FEM full dam model was adopted to analyze the seismic responses of a concrete gravity dam, in which, dynamic interaction between dam-foundation, dam-water, energy radiation, dynamic contact between monoliths, etc. were taken into consideration. Comparison was made among the numerical results of a full dam model with a massless foundation, full dam model with or without contraction joints, differences between them and realistic understanding were discussed and proposals were given to improve the aseismic capacity of concrete gravity dams.
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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...
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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 between dam and foundation affects the dam response as well, including reflection, diffraction and radiation of seismic waves. In the paper, a three-dimensional FEM full dam model was adopted to analyze the seismic responses of a concrete gravity dam, in which, dynamic interaction between dam-foundation, dam-water, energy radiation, dynamic contact between monoliths, etc. were taken into consideration. Comparison was made among the numerical results of a full dam model with a massless foundation, full dam model with or without contraction joints, differences between them and realistic understanding were discussed and proposals were given to improve the aseismic capacity of concrete gravity dams.
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Concrete hydraulic structures such as: Dams, Intake Towers, Piers and dock are usually recognized as" Vital and Special Structures" that must have sufficient safety margin at critical conditions like when earthquake occurred as sa...
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Concrete hydraulic structures such as: Dams, Intake Towers, Piers and dock are usually recognized as" Vital and Special Structures" that must have sufficient safety margin at critical conditions like when earthquake occurred as same as normal servicing time. Hence, to evaluate hydrodynamic pressures generated due to seismic forces and Fluid-Structure Interaction (FSI); introduction to fluid-structure domains and interaction between them are inevitable. For this purpose, first step is exact modeling of water-structure and their interaction conditions. In this paper, the basic equation involved the water-structure-foundation interaction and the effective factors are explained briefly for concrete hydraulic structure types. The finite element modeling of two concrete gravity dams with 5 m, 150 m height, reservoir water and foundation bed rock is idealized and then the effects of fluid domain and bed rock have been investigated on modal characteristic of dams. The analytical results obtained from numerical studies and modal analysis show that the accurate modeling of dam-reservoir-foundation and their interaction considerably affects the modal periods, mode shapes and modal hydrodynamic pressure distribution. The results show that the foundation bed rock modeling increases modal periods about 80%, where reservoir modeling changes modal shapes and increases the period of all modes up to 30%. Reservoir-dam-foundation interaction increases modal period from 30% to 100% for different cases.
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