On the Importance of Solar Radiation and Shading for the Alkali–Aggregate Reaction Prediction of Concrete Arch Dams

Abstract

The environmental conditions to which dams are exposed play a major role in dictating the progression and manifestation of the alkali–aggregate reaction (AAR). However, in the numerical thermal-mechanical simulation of AAR-affected dams, the solar radiation and its associated shadow effects have received little attention. The spatiotemporal distribution of the solar radiation incidence on the dam surfaces has often been addressed in a simplified way or has just been neglected. Yet, far less attention has been given to shadows cast by the dam’s own geometry or the slopes. The main reasons for these simplifications derive from the fact that contrary to other thermal loads, environmental actions vary in daily and annual cycles, with the added complication that solar radiation also depends on the orientation of the surface with respect to the Sun’s rays. In this way, a conventional thermal finite element code should be modified in order to deal with these two particular issues. Therefore, this article starts with the estimation of the solar radiation distribution by recourse to concepts of astronomy and computer graphics. Then, to illustrate the influence of the nonuniform temperature distribution on dam surfaces due to solar radiation and shading, the analysis of an AAR-affected arch dam is presented in this paper. A comparison of the AAR expansions computed on the dam with or without considering the solar radiation and shading is presented.

Keywords

• solar radiation
• shadow
• alkali–aggregate reaction
• concrete dams
• finite elements