Appurtenant Features Of Dams

Appurtenances are structures and equipment on a project site, other than the dam itself. They include, but are not limited to, such facilities as intake towers, powerhouse structures, tunnels, canals, penstocks, low-level outlets, surge tanks and towers, gate hoist mechanisms and their supporting struc tures, and all critical water control and release facilities. Also included are mechanical and electrical control and standby power supply equipment located in the powerhouse or in the remote...

Boundarylayer Theory

For fluids with small viscosity such as air and water with a high degree of accuracy, we can consider frictionless flow over entire fluid except for their regions around the contact areas. Here, because of high velocity gradients, we could not properly neglect frictions (Newton's viscosity law) so we consider these regions apart from the main flow, terming the boundary layers. In 1904 Ludwing Prandti introduced the concept of boundary layer and showed how Navier-Stokes equations could be...

Coupling Matrix Of The Damreservoir

The coupling matrix relates the pressure of the reservoir and the forces on the dam-reservoir interface as following where f is the force vector acting on the structure due to the hydrodynamic pressure. Figure shows a line element on the interaction boundary of the damreservoir. The work done by the hydrodynamic pressure on the interaction surface of the structure must be equal to the work of the equivalent nodal forces on the interface boundary of an element. Thus, for unit thickness elements...

Dam Reservoir Boundary Condition

At the surface of fluid-structure, it is clear that there must be no flow across the interface. This is based on the fact that face of the concrete dams are impermeable. This results into the condition that at the normal to the boundary there is no relative velocity or another word we can write it mathematically in which n is the unit normal vector to the boundary at the dam-reservoir interface and vn and vn are the velocity of the structure (dam) and fluid along the n respectively (figure...

Dams Designed for Water Supply

It is impossible for a civilization to survive without a constant fresh water supply, since it is a basic need of all humans. In many parts of the world, the freshwater supply fluctuates from enormous amounts during the rainy season to long droughts during the dry season. for this reason dams were invented to store large amounts of water from the end of the rainy season until the end of the dry season, to ensure a constant supply of water. The oldest dam in the world is the Jawa dam found 100...

Development of the Modern Dams

Unlike past periods in history, the modern dam is designed using specific principles. The largest change in the design of a modern dam compared to the earlier dams, has been the formation of engineering schools. This changed the individualistic craftsmanship of engineering into a profession based on scientific principles. Engineers were subdivided into specific disciplines, increasing the advancements of both dam principles and construction methods. The modern embankment dam has improved...

Discrete crack propagation model DCPM variable mesh

In the DCPM, global approach, a crack is represented as a discrete gap along the inter-element boundary. The growth of the crack is determined by strength or fracture mechanics based constitutive models. The progressive physical discontinuity in the system is reflected instantaneously in the finite element model by modifying the mesh during the analysis. It is generally argued that the nonlinear response of concrete dams is dominated by a few discrete long cracks. From this consideration, the...

Ecologicalenvironmental Consideration Of Dam Operation

The following observations are generalized from the literature at large. Whether any particular concern applies to any particular dam is a function of a suite of factors that might include the dam's type (e.g. concrete or earth), its purpose (e.g. hydrologic regulation, hydroelectric generation, tailings impoundment), its size, location and operating protocol (e.g. timing of drawdowns, epilim-netic versus hypolimnetic draw, peaking versus base load generation, etc.). Finally, The observations...

F Kj Kj Kjjj KC

Several functional forms of equation 5.1 have been proposed in the literature. In LEFM models, a sudden release of stress on the surface is assumed with the extension of the crack. Most investigators adopt the discrete crack propagation finite element model (DCPM) with the LEFM constitutive models. Techniques to apply the LEFM criteria in smeared crack propagation finite element model have also been reported in the literature. Pekau et al. (1991) have proposed a numerical procedure to apply the...

Famous Dams Of The World

Rogun and Nurek, in Tajikistan, are among the world's highest dams. They rise to a height of more than 1,000 feet (300 meters) each. Some of the world's other major dams are Grande Dixence and Mauvoisin, in Switzerland Chicoasen, in Mexico Inguri, in Georgia Sayano-Shushensk, in Russia Mica, in Canada and Guavio, in Colombia. Three of the foreign dams that are constructed of the largest volume of materials are Tarbela, in Pakistan Lower Usuma, in Nigeria and Guri, in Venezuela. Dams that form...

Free Surface Boundary Condition

The geometry of free surface boundary is not known a priori. This shape is part of the solution, which means we have a very difficult boundary condition to cope with. In the case of surface wave of negligible surface tension, we call them gravity wave. The free surface of a wave can be described as where p is the displacement of the free surface above the horizontal plane, say z 0,. If the surface varies with time, as would the water surface, then the total derivative of the surface with...

Ft [M U

The mass matrix M is a diagonal matrix and in general it can be a nondiagonal symmetric matrix. The forces due to elasticity can be written as where K is the stiffness matrix. A detailed description of the stiffness matrix can be found in finite element books. The damping matrix can be written as

General Form Of Reservoirs Equation Of Motion

Fluids are composed of molecules in constant motion and collisions. A fluid has no structure. They are not distinguished by their microscopic (molecular) structure. To take account of each molecule in a flow, may be difficult for engineering purposes. Instead we are interested in average measuring of the molecule manifestations such as density, pressure and temperature which are their macroscopic structure. The continuum concept offers a great deal of simplification in analysis. A fluid point...

Introduction

The cracking behaviour of concrete dams has been the subject of extensive research during the past decade because few dams suffered severe cracking during earthquakes. Rescher (1990) indicated that most concrete gravity dams will experience cracking even under operational loading conditions and moderate earthquake ground motions. Therefore, the assumption of linear behavior may not be appropriate in the analysis of the seismic response of concrete gravity dams. Concrete dams are distinguished...

Irrigation Dams

A steady supply of water for irrigation is extremely important for any civilization to thrive. Heavy flooding in the wet season and long droughts in the dry season makes farming very difficult. However, if the water is contained during the wet season and released periodically through the dry season, a constant water supply will be present. The first dam designed for irrigation purposes was the Marib dam in Yemen Capital City of Saba. The Marib was an embankment dam constructed about 510 BC. It...

Linear Momentum Equation

If we take linear momentum as parameters N which is used as a general term (vector and scalar) in the Reynold transport equation, we have N P mv. The term n in this case would become momentum per unit mass, or simply v, then, P JJJ v(pdV). Then the Reynold transport equation can be written as followings The equation of linear momentum is a vector equation and can be divided into its three components. In above equation, F if the resultant of the all external forces acting on the system and v the...

M i d[CoM

Since Y is a quadratic function of strain, it is positive and, thus, d is always increasing as shown in equation 5.9. This is a characterization of the irreversibility of damage. Different hypothesis have been proposed for isotropic damage model. The basic assumption in behaviour of the damaged and equivalent undamaged element will results in different model. Among several models, special attention will be given to the two models. They are mainly based on two concepts of the modelling. In the...

Mn Mm

Figure 3.4 An example of MDF system with two degrees of freedom at each mass For a system of MDF system when subjected to ground acceleration in two directions and there are two degree of freedoms for each mass,as shown in figure 3.4,we can write the equation of motion based on the both degrees of freedom at each mass.For this system, we can write the displacement vector as The same can be written for U and U . The equation of motion can be written as following m u + c U + K u f (t) - m u9 When...

Nonlinear Modelling Of Concrete Dams Using Damage Mechanics

Micro cracking in concrete is believed to occur at relatively low levels of loading. Therefore, cracking progresses in a heterogeneous medium because of an increase in micro cracking, and because of the linking of various micro cracked zones. Experiments performed on cement paste as well as concrete show that micro cracking has an arbitrary orientation. When the load is increased, macroscopic cracks develop and the crack orientations follow the principal stress directions in the material....

Reservoir Boundary Conditions

The formulation of the boundary conditions associated with the reservoir boundaries is simply the expression in mathematical terms of the physical situations. There are an infinite number of solutions to the differential equation. The task is to find the solution that is relevant to the boundary condition. It should be noted that in addition to the spatial (or geometric) boundary conditions, there are temporal boundary conditions which specify the state of the variable of the interest at some...

Reservoir Farend Truncated Boundary Condition

The truncated boundary for the finite element and boundary element modeling of the infinite reservoir was worked by so many researchers. Sommerfeld boundary condition is the most common one that is based on the assumption that at long distance from the dam face, water wave can be considered as plane wave. A plane wave can be represented by an equation of the form in which n is the normal at the truncation boundary. This represents well-known Sommerfeld radiation condition. It introduces a...

Reservoir Foundation Boundary Condition

If there is no absorption or penetration of water into the reservoir bottom, the same dam-reservoir boundary condition that was obtained previously, can be used for reservoir-foundation boundary. In case of reservoir with sediment at the bottom, we can account it in a very simplified manner. The boundary condition at the reservoir bottom relates the hydrodynamic pressure to the sum of the normal acceleration and acceleration due to interaction between impounded water and the reservoir bottom...

Safety Of Dams And Reservoirs

There are Several types of reservoirs as defined by their locations. The common type is a reservoir behind a dam in a valley. Increasing use is being made of tidal-storage reservoir for power generation along coast lines and excavated reservoirs for water storage for municipal or other use. In the latter type the excavated material commonly is employed to construct an embankment on one or all sides of the reservoir. Reservoirs and their associated dams serve many purposes including electric...

Seismic Energy Balance

In the design of structure subjected to earthquake loading, the energy equation can be used to study the energy absorbtion of different components. In a satisfactory design, the energy supply must be larger than the energy demand. In this regard, two approaches can be considered for the energy equation. Uang and Bertero (1990) used absolute and relative energy formulations for a single degree of freedom system. They found that absolute energy formulation is simple and more straightforward....

Single DegreeOfFreedom Systems

A single-degree-of-freedom system (SDF) is defined as a system whose motion can defined by a single parameter. Systems shown in figure 3.1 are systems of SDF. As shown in the figure only one parameter (u, x or 0 ) is required to define the position of the particle at each second. For a system shown in 3.1 a, if we try to apply a dynamic force f (t), the equation of the motion can be written as Figure 3.1 Systems of single degree of freedom

The Moslem World

Arabs quickly developed their country within one century after the impact of new Islamic religious founded by prophet Mohammed. Several irrigation dams around the new power centres of Mecca and Madina, were built. The following is a summary of 7th and 8thcentury dams in central Arabia. Table 1.4 Summary of 7th and 8th century dams in central Arabia All of these dams were of the gravity type. They all have two outer walls of dry masonry and an earth or rubble core in between. The walls of some...

Using Newmark Method For The Coupled Equations

Direct integration scheme is used to find the displacement and hydrody-namic pressure at the end of the time increment i + 1 given the displacement and hydrodynamic pressure at time i. The Newmark- method is used for discretization of both equations (implicit-implicit method). In this method U j+i, U j+i, P j+i and P i+1 can be written as follows U i+i U p+i + 7Ai U i+i (4.3) U i+i U p+i + At2 U i+i (4.4) U P+i U i + At U7 i + (0.5 - )At2 U i P i+i P P+i + Y At p m (4.5) p i+i p +i + Ai2 p m...

Embankment Dams

A broad spectrum of natural and fabricated materials have been used in the construction of embankment dams. Embankment dams are made by building an embankment of gravel, sand, and clay across a river. To prevent leakage, often a core, or inner wall, of concrete or other watertight materials is used. In a rolled-fill dam, earth is hauled by vehicles onto the dam and rolled tight with heavy machinery. In the hydraulic fill dam, earth is carried to the dam by water in pipes or flumes and also...

The Equation of the Motion

The continuity equation and the linear momentum equation was developed for finite systems and their were related to control volume. The equations give an average values of quantities or only components of resultant forces. They don't give any detail information of the flow everywhere inside the control volume. Here, we are trying to find out differential equations valid at any point of fluid. Writing continuity equation in the form of differential equation, we consider an infinitesimal control...

Reynolds Transport Equation

Consider N as properties of a substance whose measure depends on the amount of the substance presented in a system. An arbitrary flow field of v v x, y, z, t is observed from some reference xyz. We consider a system of fluid with finite mass at time t and t At figure 2.3 . The streamlines correspond to those at time t. The control volume is considered with system at time t and is fixed. The distribution of N per unit mass will be given as n, such that N HI npdV with dV representing an element...

[MU [CU [KU f [MUg

In a MDF sytem, a system is discretized into its degrees of freedom. The number of degrees of freedom depend on the number of elements and the degree of freedom for each element. Usually in the case of concrete gravity dams isoparametric plane stress or plane strain are used. These types of elements are used for two dimensional problems. In some cases triangular elements may be used. In both plane stress or plane strain the displacement field is given by the u and v in directions of cartisian x...

E doE Gf doGf

5.6.8 ANALYTICAL PROCEDURES IN A FINITE ELEMENT MODEL In a finite element model, the four-node isoparametric element is preferred in the implementation of the local approach of fracture-based models and has been used for the implementation of the described constitutive model. The standard local definition of damage is modified such that it refers to the status of the complete element. The average of the strain at the four Gauss points is obtained and the damage is evaluated from the...

Concrete Arch and Dome Dams

Gordon Dam Design Section

The ultimate complexity of design and analysis of stresses is attained in arch and dome dams. These dams are thin, curved structures commonly containing reinforcing, either steel rods or prestressed steel cables. Volume requirements for aggregate for manufacture of concrete are much less than in gravity and gravity-arch dams, but the competency of bedrock in foundations and abutment to sustain or resist loads must be of a high order. Arch dams usually are built in narrow, deep gorges in...