Retrofitting Of Large Water Retaining Structures To Withstand Earthquakes

Abstract

In many parts of the world, large water-retaining structures, including dams, were built during 1910-1960. Many of these dams have experienced alkali-silica reactions within the concrete and also have exhibited a lack of bonding stresses across horizontal construction lift surfaces. This is a result of using old construction techniques. With advancement o f knowledge in earthquake engineering, these dams have been found to fail the modern seismic safety criteria. All such structures must now be analyzed for gravity-, reservoir-, temperature-, and earthquake-induced loads. The author has carried out several studies on different dams and has found that many dams are unsafe for earthquake conditions. Several methods for retrofitting exist, including strengthening of the dam by the use of epoxy-coated post-tensioning cables. This paper provides a case study of a 64.6-meter high double curvature thin dam structure that has been re-strengthened by the use of vertical post-tensioned cables. This paper summarizes various laboratory, field, construction, and performance studies for such large water-retaining structures. The techniques described here are applicable to other dam structures that are threatened by their exposure to maximum credible earthquakes.