Comparison of Design and Analysis of Concrete Gravity Dam

Abstract

Gravity dams are solid concrete structures that maintain their stability against design loads from the geometric shape, mass and strength of the concrete. The purposes of dam construction may include navigation, flood damage reduction, hydroelectric power generation, fish and wildlife enhancement, water quality, water supply, and recreation. The design and evaluation of concrete gravity dam for earthquake loading must be based on appropriate criteria that reflect both the desired level of safety and the choice of the design and evaluation procedures. In Bangladesh, the entire country is divided into 3 seismic zones, depending upon the severity of the earthquake intensity. Thus, the main aim of this study is to design high concrete gravity dams based on the U.S.B.R. recommendations in seismic zone II of Bangladesh, for varying horizontal earthquake intensities from 0.10 g - 0.30 g with 0.05 g increment to take into account the uncertainty and severity of earthquake intensities and constant other design loads, and to analyze its stability and stress conditions using analytical 2D gravity method and finite element method. The results of the horizontal earthquake intensity perturbation suggest that the stabilizing moments are found to decrease significantly with the increment of horizontal earthquake intensity while dealing with the U.S.B.R. recommended initial dam section, indicating endanger to the dam stability, thus larger dam section is provided to increase the stabilizing moments and to make it safe against failure. The vertical, principal and shear stresses obtained using ANSYS 5.4 analyses are compared with those obtained using 2D gravity method and found less compares to 2D gravity method, except the principal stresses at the toe of the gravity dam for 0.10 g - 0.15 g. Although, it seems apparently that smaller dam section may be sufficient for stress analyses using ANSYS 5.4, it would not be possible to achieve the required factors of safety with smaller dam section. It is observed during stability analyses that the factor of safety against sliding is satisfied at last than other factors of safety, resulting huge dam section to make it safe against sliding. Thus, it can be concluded that it would not be feasible to construct a concrete gravity dam for horizontal earthquake intensity greater than 0.30 g without changing other loads and or dimension of the dam and keeping provision for drainage gallery to reduce the uplift pressure significantly

An Empirical Comparison of Multiple Linear Regression and Artificial Neural Network for Concrete Dam Deformation Modelling

“…According to the reasons mentioned above, this paper chooses (7) and (9) to study the deformation monitoring model of concrete dams. Therefore, the input variable of the single point deformation prediction model is…”

“…The statistical model assumes that the components are completely independent and may not match the actual situation [5]. At present, the most common statistical 2 Mathematical Problems in Engineering models are based on regression methods such as the multiple linear regression (MLR) [6], stepwise regression (SR) [7], principal component regression (PCR) [8], and partial least squares regression (PLSR) [9]. By gradually screening regression factors of MLR models, SR models obtain regression coefficients at a certain significance level, results more accurate than those obtained by the general least square method.…”

Hydrologic and Structural Safety Evaluation of Aged Concrete Gravity Dam Using Finite Element Method

“…The failure modes of a concrete gravity dam may be due to overturning, sliding or crushing [1]. According to Ali et al the overturning or rotational failure about the toe will occur when the point of intersection of the dam base and the line of action of the resultant of all forces acting on the dam lays downstream of the toe i.e.…”

“…According to Ali et al the overturning or rotational failure about the toe will occur when the point of intersection of the dam base and the line of action of the resultant of all forces acting on the dam lays downstream of the toe i.e. outside of the base [1]. On the other hand, crushing failure may take place if the inherent strength of the dam material fails to withstand the stresses produced due to various loading.…”

“…This indicates compression and tension failures will occur due to an exceedance of the allowable compressive and tensile strength of the dam material respectively. Further, Ali et al added sliding or shear failure will occur when the frictional resistance along the base or any horizontal plane is unable to resist the net resultant horizontal force above the respective plane [1].…”