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... 

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... 

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... 

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 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... 

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... 

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... 

Dam failures can result in massive property damages and a large loss of life. Safety management and risk assessment of dam failure have great significance to governments. Estimating the safety level of existing dams is an important part of dam safety management program in order to improve its safety and to achieve an acceptable level and to provide emergency action plans for probable failures. Reaching this goal requires a good sense of the actual condition of the dam, identification of hazards and selection of the appropriate scenario of safety level estimation in accordance with these conditions. In this way, prediction of life loss is an important factor that must be considered. This... 

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... 

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... 

Safety of concrete gravity dams under dynamic loading that cause from earthquakes is an important aspect of research.as we know, dam structure response is related to type of loading, properties of concrete and foundation material, so according to the uncertainties of these random variables, in this research we calculate the response (stresses) of structure for different value of random variables that have their own probability distribution type. Nonlinear plasticity damage model of dam is implemented in ABAQUS and for reliability analysis we use Latin Hypercube Sampling (LHS). Sensitivity results show that PGA of earthquake and Special Energy (Gf) of concrete in comparison with concrete... 

Electrical power is an inseparable part of human life. Therefore, design and analysis of electrical transmission towers have always been important for scientists. In common design methods due to the lightness of these structures only the wind load is considered and earthquake effects are neglected. On the other hand, regarding regulation No.2800 a lot of areas of Iran are located in earthquake zones. Therefore, it is necessary to evaluate the performance of these structures against earthquakes. In this research, regarding conducted studies, we decided to use incremental dynamic analysis method (IDA) in order to evaluate seismic performance of the tower. In sake of thoroughness of the... 

A finite element model for seismic analysis of concrete arch dams is proposed. Material inelasticity as well as joints nonlinearity is considered. In order to provide a precise description of concrete response, a novel plastic-damage constitutive model for plain concrete is developed. For this purpose, the microplane theory is proposed for overcoming the deficiency of available anisotropic continuum plastic-damage models in reproducing the true anisotropic nature of damage in multidimensional loadings.Based on the microplane theory, the degeneration process in concrete is considered along with plastic deformations. Using the principle of strain energy equivalence, a transformation between... 

Global collapse in earthquake engineering refers to the inability of a structural system to sustain gravity loads when subjected to seismic excitation. Dynamic instability phenomena in exist buildings have a key position and for this reason strict criteria in structural seismic assessing codes presented for avoiding this phenomena. At this study, dynamic instability of five designed concrete buildings with moment frame system, mixed up 3, 6, 9, 12 and 15 story building, are investigated. P-delta effects, deterioration in strength and stiffness and cyclic deterioration in structural components considered in this investigation. For modeling nonlinear behavior of elements, experimental results... 

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... 

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... 

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... 

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...