Forces on a gravity dam pdf

Pressure acts through the center of gravity of the water column resting on the sloping upstream face. A gravity dam is designed in such a way that it resists all external forces acting on the dam like water pressure, wind pressure, wave pressure, ice pressure, uplift pressure by its own selfweight. Gravity dam, seismic forces, sliding, stability, analysis. Concrete and masonry dams the national academies press. Failure of gravity dams causes and its failure modes.

F density of water acceleration of gravity height of the water2 width of the dam x height of the water. Ppt gravity dam powerpoint presentation free to view id. Sound rock capable of resisting dynamic forces including earthquake. Forces water pushes against the gravity dam, but the heavy weight of the dam pushes down into the ground and prevents the structure from falling over.

The intensity, direction and location of these forces mu st be estimated by the engineer after consideration of all available facts and, to a certain extent, must be based on judgment. Gravity dams may be classified by plan as straight gravity dams and curved gravity. A gravity dam has been defined as a structure which is designed in such a way that its own weight resist the external forces and this type of structure is most durable and solid. The gravity dam has sufficient weight so as to withstand the forces and the overturning moment caused by the water impounded in the reservoir behind it. This cross section eventually evolved into the common triangular cross section design of todays gravity dams. Seismic forces and stability analysis of gravity dam.

Online courses for civil engineering covering full. The epicentre of the shock was computed by the us coast and geodetic survey at about 17. Forces acting on a gravity dams with diagram geography. Gravity dam loads on concrete dams loads can be classified in terms of applicabilityrelative importance as primary loads, secondary loads, and exceptional loads. Forces acting on a dam structure and calculations the constructor. Forces acting on gravity dams 1 dam force free 30day trial. Design and construction of concrete gravity dams nptel.

Horizontal pressure by the water at the upstream and downstreamtail water. A gravity dam is a dam constructed from concrete or stone masonry and designed to hold back water by primarily using the weight of the material alone to resist the horizontal pressure of water pushing against it. The imposed 2d analysis for a 3d problem led to additional useless expenses. Failure of gravity dam occurs due to overturning, sliding, tension and compression. Many of the forces which must be cons idered in the design of the gravity dam structure are of such a nature that an exact determination ca nnot be made. For example, gravity forces can be calculated using newtons law of gravitation. Different forces acting on gravity dam civil engineering. Forces can be classified as external wind, gravity or internal. Scribd is the worlds largest social reading and publishing site. Forces acting on a gravity dam gravity dam computation of. Different types of forces acts on a dam structure such as water pressure, self weight, wave pressure etc. In very cold conditions, the reservoir gets covered with a layer of ice. Loads can be classified in terms of applicabilityrelative importance as. Body force acts horizontally at the centre of gravity and is calculated as.

By researching the size and direction of all the forces acting on a dam, engineers design a structure that is able to resist all these forces. Seismic response of a concrete gravity dam considering hydrodynamic effects a. When this layer is subjected to expansion and contraction due to variation in temperature, a force is developed which acts on the dam at level of water in the reservoir. The most ancient gravity dam on record was built in egypt more than 400 years b. Mass of dam pseudostatic inertia and hydrodynamic loads are determined from seismic coefficients. They have a solid upstream side supported on the downstream side by a series of buttresses. A gravity dam can be combined with an arch dam into an arch gravity dam for areas with massive amounts of water flow but less material available for a purely gravity dam. The magnitude of forces, their direction, and their point and plane of application influence how they affect. Previous ferc gravity dam guidance dealt with nappe forces by ignoring the weight of the nappe on top of the structure and by requiring that the. The area refers to the surface of the dam that come into direct contact with the water.

It requires less maintenance and it can be constructed with masonry or concrete. Structural stability and 2d finite element analysis of. Forces acting on gravity dams 1 free download as word doc. Simple stability analysis of gravity dam showing effect of uplift on base of dam and at other sections. Unit weight of concrete 24 knm 3 and masonry 23 kn. A gravity dam is an essentially solid concrete structure that resists imposed forces principally by its own weight. Therefore, these forces must be conservatively estimated when used as a stabilizing force in a stability analysis. Deformation may be caused by reservoir load, earthquake forces, arch dam thrust, unfavorable orientation of the cracks in the rock with respect to the load directions imposed by the dam or reservoir, large ranges of tem perature, freezing and thawing of water within the cracks in the rock, soft ening of the contact surfaces between rock. A curved gravity dam resists the external forces by its weight and not by arch action. Forces acting on gravity dam load combination for design design method of gravity dam loads on arch dams method of design buttress dam. Later gravity dams used a trapezoidal cross section. Stable valley and abutment slopes foundation with elastic constants preferred water tight reservoir in order to resist erosion and adverse effects of wetting, drying, freezer and thawing. Concrete gravity dams are often used for hydroelectric power projects. The design of rcc gravity dams is similar to conven.

The inward compression of the dam by the water reduces the lateral horizontal force acting on the dam. Gravity dam criteria for selection of site for a gravity dam. Taking these three forces into account the uplift, the water thrust and the weight of the dam the accepted rule is that the resultant of these forces should pass within the middle third of the section being analysed. This class of loading is taken when ice force is serious.

The principle force acting on a dam is the weight of the water behind the dam. Pdf on december 10, 1967, at 22 h 5 min gmt, western india was shaken by a severe earthquake. Forces imposed on dam, especially seismic forces are nonlinear. It is the pressure of water that acts perpendicular on the upstream face of the dam.

Gravity dams are constructed from masonry or concrete. Aug 03, 2017 dam with water at its full reservoir level is subjected forces due to iwater pressure. How many forces acting on a dam structure and calculations. A force is a push or pull acting upon an object as a result of its interaction with another object. Gravity dams gravity dams criteria for selection of dam site, construction material, forces acting on gravity dam, modes of failure, stability analysis, safety criteria, methods of design, stress analysis and stress contours, galleries, instrumentation, joints, keys, water seals, temperature control in concrete dams, foundation treatment. A gravity dam is a concrete structure designed so that its weight and thickness insure stability against all the imposed forces. It transfers the loads to the foundations by cantilever action and hence good foundations are prerequisite for the gravity dam. Breaking this formula down even further, we can write. Weight of the dam per unit length is equal to the product of the area of crosssection of the dam and the specific weight or unit weight of the material. Dworshak is a gravity dam with the maximum height of 219 m and maximum bottom width of 152 m, the concrete volume is 525. Design of gravity dam, calculation in reservoir full. Some of these forces can be described by universal laws.

All the predominant forces that act on the dam have been. A detailed sketch of a gravity dam is shown in fig. Water pressure forces are diverted to the dam foundation through vertical or sloping buttresses. Forces on gravity dam irrigation engineering youtube. Concrete buttress dams are a specific type of gravity dam. Further details on temperature control methods are provided in chapter 6. Dam with water at its full reservoir level is subjected forces due to iwater pressure. Seismic response of a concrete gravity dam considering.

Middle vaitarna dam submitted in partial fulfillment of the. Gravity dams are designed so that each section of the dam is stable and independent of any other dam section. On december 10, 1967, at 22 h 5 min gmt, western india was shaken by a severe earthquake. A concrete gravity dam is a massive concrete structure, roughly triangular in shape, and designed so that its weight ensures structural stability against the hydrostatic pressure of the impounded water and other forces that may act on the dam. The forces that come in this category are weight of the dam, weight of water acting on inclined faces of the dam, uplift pressure etc. Previously in this lesson, a variety of force types were placed into two broad category headings on the basis of whether the force resulted from the contact or noncontact of the two interacting objects. The dam must be strong and sturdy and have strong connections to the ground, in the form of foundations, to help it stand. This force acts linearly along the length of the dam at the reservoir level. Forces acting on gravity dam and their magnitude and line of action. Elementary profile of a dam subjected only to external water pressure on upstream side, will be right angled triangle, having zero width at water level and a base width b at bottom, i. Water vibration produces a force on the dam acting horizontally. The first version of a modern gravity dam was built between 1765 and 1800 in mexico.

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