Volume XV Issue 4

Temperature variation and the associated thermal stresses and strains must be evaluated to define initial loading conditions for development of defensive measures and dam safety analysis. Temperature in concrete dams has direct effects in thermoelastical properties of concrete mixture and can affect creep and alkali aggregate reaction.

In concrete arch dams, because of the particular geometry, solar radiation shares of exposed surfaces vary spatially through the downstream face. In this case, three-dimensional analysis is unavoidable.

A three-dimensional finite element modelling procedure is presented to determine the thermal response of concrete arch dams. Appropriate heat transfer boundary conditions in the dam body were used to define and approximate the air and reservoir temperature as well as solar radiation variations. A finite element model is used to determine annual variation of temperature in the body of Karaj arch dam in Iran as a case study. The rate of convergence of the numerical solution is examined. The temperatures predicted by the model are satisfactorily compared with the instrumentation records at Karaj dam.

Results of the finite element analysis show that the highest temperature and temperature gradient occurs in a very narrow region of the downstream face. The difference between the temperatures of the points located on the exposed surface (especially the downstream face) at the same elevation across the dam axis for an instant is considerable. This is due to the effect of solar radiation. Therefore two dimensional analysis of an arch dam cannot yield accurate results and three dimensional analysis is necessary.

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