Concrete Arch and Dome Dams

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 mountainous regions where access and availability of construction materials pose especially acute problems. At sites where abutments are not entirely satisfactory rock may be excavated and replaced with concrete to form artificial abutments. Their height can be as high as 272 m (905 ft).

Arch dams are of two kinds. Constant-radius arch dams commonly have a vertical upstream face with a constant radius of curvature. Variable-radius dams have upstream and downstream curves (extrados and intrados curves) of systematically decreasing radii with depth below the crest When a dam is also doubly curved, that is, it is curved in both horizontal and vertical planes, it is sometimes called a "dome" dam. Curves that have been used in construction of arch or dome dams are arcs or sectors of circles, ellipses, or parabola. Some dams are constructed with two or several contiguous arches or domes, and are then described as multiple arch or multiple-dome dams. Figure 1.2 shows Cross-section of several varieties of arch dams.

Engineering analysis of arch and dome dams assumes that two major types of deflections or dislocations affect the dam and its abutments. Pressure of water on the upstream face of the dam and, in some instances, uplift pressures from seepage beneath the dam, tend to rotate the dam about its base by cantilever action. In addition, the pressure of reservoir water tends to flatten the arch and push it downstream, so that stresses are created which act horizontally within the dam toward the abutments. That portion of the bedrock abutment which receives the thrust from the load of reservoir water either by a tendency for downstream movement of the dam or flattening of the arch is called the thrust block and must be sufficiently strong to resist the forces acting on it without failure or appreciable, dislocation. Simply stated, an arch dam utilizes the strength of an arch to resist the loads placed upon it by the familiar "arch action". It is clear that the foundation and abutments must be competent not only to support the dead weight of the dam on the foundation but also the forces that are directed into the abutments because of

Gordon Dam Design Section

arch action in response to loads created by impounded reservoir water, and, in areas of cold climates, pressures exerted by ice forming on the reservoir surface. In regions of seismic activity consideration must also be given to the interaction of the dam and pulses of energy associated with earthquakes.

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  • Makda
    How to design a dome eurocode 2?
    6 years ago

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