Forces Acting on Arch Dams

Forces Acting on Arch Dams

Generally, the same forces act on arch dam, which do act on a gravity dam. These forces are: (i) water pressure; (ii) Uplift pressure; (iii) earthquake forces; (iv) silt pressure; (v) wave pressure (vi) ice pressure; as discussed in article. However, the relative importance of the forces is difference in an arch dam, as compared is small and is generally neglected, because of the narrow base width of its body. On the other hand, the stresses caused by ice, temperature changes, and yields of supports (i.e. abutments), generally become quite important in arch dams, and hence must be thoroughly examined.

Whereas, the ice pressure, applicable in cold countries, causes a continuous concentrated load along the arch element at the elevation of the ice; the internal stresses caused by the temperature changes move the dam upstream during the summer and downstream during the winter. Hence the low water temperatures become quite important in stress analysis, since these stresses act additive to the reservoir water pressure. Moreover, even the slight yield of abutments due to transfer of load by arch action, may also cause high internal stresses in the arch, and state therefore, be prudently accounted for.

Designs of Arch Dams

Arch dams can be designed on the basis of any one of the following three methods:

1.     Thin cylinder theory;

2.     Theory of Elastic arches; and

3.     The Trial load method.