Sharif Digital Repository

One of the major reasons causing cracks in external surfaces of concrete arch dams are thermal loads. Therofore, in order to avoid instabilities due to function of thermal loads in association with hydrostatic and hydrodynamic pressures, a precise evaluation of temperature distribution through dam body is indispensable. In this study, effects of thermal loads mostly on upstream surface of Karun-3 concrete arch dam in Iran were examined using a 3-D finite element method considering water level fluctuations. Also the influence of operatvie boundry conditions in our problem which are water temperature, air temperature and solar radiation was precisely taken into account. Moreover, nonlinear... 

In recent years, the construction technique in dam engineering has been revolutionized due to the rapid development of roller compacted concrete (RCC) and By making the continuous construction of dam without contraction joints, the goal of more economical and faster concrete dam construction has been realized. The typical stress-strain behavior of traditional concrete and high cementations content RCC results in a reasonably constant modulus of elasticity that is valid for stresses ranging from zero to near ultimate strength. But lean RCC mixes typically have nonlinear stress strain behavior with hardening after stresses exceed about 25% of the ultimate strength. Using the nonlinear... 

Concrete gravity dams are structures of much importance which their failure due to earthquakes results in a catastrophe. Therefore, precise stability analysis of these types of dams against sliding and overturning is essential. The common method of safety assessment of gravity dams is based on limit equilibrium method assuming that dam slides and overturns as a rigid structure. Although providing high safety factors is somehow acceptable to meet the safety requirements of dams, it should be considered that the whole system of dam body and foundation is flexible in reality and its performance should be studied in this case for stability analysis. In this investigation, first, stability... 

Usually in analysis of arch dams, applied seismic motions on dam-foundation interface are assumed to be uniform. This is while that recorded motions show non-uniform accelerations in dam-foundation interface. Analyzing of the dam under this non-uniform accelerations we can find the importance of this assumption in analysis of arch dams. Two earthquakes were excited “KAROON III” dam at 20.11.2007 and 21.11.2007. The respective motions were recorded by the array of accelerometers that has been installed on the dam. The recorded motions, indicated non-uniformity of excitations in accelerometers were installed near the dam-foundation interface. Therefore this data provided an opportunity to... 

Large structures such as dams, long span bridges and piping systems because of an extended interface with the ground as support and the earthquake wave propagation in foundation are subjected to the non-uniform excitations. In such cases, the standard dynamic analysis in which a uniform earthquake is used as an input data is not true and can lead to unrealistic results. In the present study, seismic responses of arch dams subjected to spatial variation of ground motions is investigated and compared with the standard methods. For this purpose the governing equations are implemented into the NSAD-DRI (comprehensive software for Nonlinear Seismic Analysis of Dams) and the seismic responses of... 

Dams are huge structures in which safety is a very important issue because a failure will result in loss of lives and finance. Several approximate equations for the approximate analysis of arch dams already exist. These equations are usually obtained by considering the behavior of the dam as a shell. Approximate methods are much faster in comparison to the exact methods and give young design engineers who do not have the experience of designing inside view of displacements, stresses and strains. The aim of this project is to compare the results of approximate analysis of arch dams with the results of finite element models and clarify the points of dams in which approximate analysis methods... 

Supplying water has almost always been the essential need of human for agricultural, industrial and drinking water use. One of the infrastructure works to catch up to this goal is dam construction. Among all of dams, concrete gravity dams have been fortunate between designers and builders of dams, because of their acceptable function against seismic loads. So, analyzing the function and stability of dams is important in different cases. Formed crack in dam body is one of the most important parameters that affect both the function and durability of a concrete gravity dam and considering the measure of the earthquake affects on the formation and expansion of crack profiles many studies have... 

Finding an initial point to start classical optimization methods is privileged to finding an algorithm. It is due to high dependency of final result to selection of initial point, which is independent of type of the algorithm. In engineering optimization where space of problem has several local extremums, this fact has higher effects. In the present study, to overcome this problem in finding optimum shape of concrete arch dams, a two-stage approach is proposed. In the first stage (discrete stage), using the developed stress-constrained topology optimization, an initial optimum shape is obtained. Afterward in the next stage (continuous stage), the optimum shape obtained from previous stage is... 

One of the most important aspects in the stability of arch dams which have been encountered, are the stability of the abutment. In order to assess the stability of wedge, Londe Method has been considered by simple assumption. Displacement and velocity of the wedge were calculated by Newmark beta method. In this study stability of abutment of Luzzone dam due to static and seismic loading was investigated. After modeling a finite element of dam-foundation-reservoir of Luzzone dam, the horizontal and vertical earthquake was applied to the model and the thrust force was recorded. By using a software stability safety factor of wedge was studied.it was found that the wedge is unstable and will... 

The dams as one of the most costly and most fundamental infrastructure that human steps to make their, always paid special attention to people in different historical periods. According to the high cost of this structure, optimum design is so important. On other hand stability of structure as main aspects of the design that in the absence of it is threatening the lives of many people in downstream. Therefor the engineers consider two important aspect when they want to design a dam. The first step in designing is determinate the external loads. A designer not only must recognize this loads but also by using the material that he consume in the body of dams reach to a safety structure in During... 

Due to the importance of concrete gravity dams, safety issues are of great importance in these structures. On the other hand, because of the uncertainty in the geotechnical characteristics of the rock foundation in the design phase, and also consider the significant affects of these parameters on seismic response of concrete gravity dams, it’s not possible to determine safety factor accurately. Since the Sliding control in the base of the dam can protect the stability of concrete gravity dams in the operation phase, this study concentrate in this subject and intends to calculate the Sliding between the dam base and the foundation with finite element analysis, considering the rock foundation... 

Thermal analysis of concrete arch dams is always an important issue in designig these enormous concrete structures. The reason this issue mainly concerns arch dams and not gravity dams is because of little thickness of arch dams which makes them prone to cracking due to thermal loading. To solve any thermal problem we need boundary conditions. In arch dam case, these boundaries are the temperature of the upstream and downstream face of the dam which, depending on circumstances, can be in touch with water or air. Estimating air temperature is a fairly easy task when you have monthly mean temperatures. The challenging part is defining water temperature in any depth of the reservoir whenever we... 

Gravity dams are solid concrete structures that maintain their stability against design loads from the geometric shape and the mass and strength of the concrete. Because of their critical role in supplying portable and agricultural water and problems which would happen if they broke, it is required to consider their stability and keep them in safe conditions. They should be able to continue their function after a disaster such as earthquake. But most of them are aged dams with some have been built near faults. Indeed, there are some concerns regarding the performance of these dams under the effect of seismic loads. This research deals with performance evaluation of concerete gravity . The... 

Concrete gravity dams are one of the most important infrastructures therefore their performance under seismic load is an important issue of concern for dam owners. It is necessary that these infrastructures to be able to continue their function after a disaster such as earthquake, as any damage can cause huge cost. For analysis of dams linear and nonlinear analyses are used. Because even operating loads will create cracks in the body of the dam, dam behavior can not always be considered linear. It is remarkable that these surface cracks can join together under seismic loads and this question the safety of dams. It is important to note that nonlinear analysis of concrete gravity dams is... 

Concrete dams are one of the most important infrastructures in any country. In recent years new safety standards, such as the analysis of concrete dams in various modes of potential failure or performance-based design are proposed. Many of existing dams may fail to meet revised safety criteria. For this reason it is necessary to control built dams with this new standards. In this reseach, fragility assessment is used for rational safety evalution and decision-making. fragility curves are defined by the probability of a structural limit. We examined the fragility curves for the nonlinear behavior and safety of the dam under earthquakes. fragility curves based on the cracking area are more... 

The most important issues in massive concrete structures such as concrete dams are the increase in temperature due to heat generated by the dam Hydration of cement in concrete. Internal restrains are created from thermal gradient between the surface and the interior of the structure. External restrains are created from connections between structures and foundation for obstruct the movement of concrete structures due to temperature change. External restrains and internal creates tensile stresses in the concrete considerable, which can lead to thermal cracks in the structure. To prevent or minimize the possibility of cracks are examined thermal studies for the design of reinforced concrete... 

One of most important type of dams are concrete gravity dams, This structures maintain their stability against the load from their weight. The study of stability of dams is very important issue because Iran is placed on a seismic zone and instability of constructed dams will cause many problems for us. There are two method in study of concrete gravity dams: in first method which is named rigid approach the body of dam consider as a rigid body and by equilibrium equations and traditional strength of material concepts the safety factors of stability and stresses are determined. In second method that is named flexible approach, we should prepare a finite element method from the dam, reservoir... 

Generally concrete dams have not been sited at location where there were faults classified as active. However, there may be sites suitable for concrete dams where there is some possibility of fault displacement occurring underneath the dam. In addition, there may be situations where an existing dam was constructed over a fault thought to be inactive and later determined to be active, due to different approaches of classification of a fault whether it is active or not. Also some discontinuities may be observed during construction. For these cases nonlinear analysis and criteria will be required to assess the capability of concrete dams to safely withstand fault displacements. In this thesis,... 

Concrete dams are important nations infra structures. They store water for different purposes such as irrigation, water supply, flood control, electric power, recreation and improvement of navigation. Safety of concrete dams is a major challenge for the owners. As a result, concrete dam’s behavior when subjected to different load condition especially an earthquake ground motion is a concern which may cause some damage. It is needed to determine concrete gravity dam’s response under different load condition. One of the important factors for determining concrete dam’s response is foundation properties and its behavior under seismic loading. A finite element model consisting of... 

The exact modeling of a concrete dam system, which includes concrete dam body, foundation, reservoir and sediment layer, plays an important role in the analysis of the interaction between the concrete dam components. In this thesis, the interaction between the components of a concrete gravity dam system is studied by Finite element method. The interactions between these components are analyzed in time domain. In this thesis, we focus on the sediment layer and its impacts on the response of the dam. The sediment layer is modeled as a two phase medium. In order to study the effects of the sediment layer on the dam response, models with different heights and materials of the sediment layer are...