Reservoir length effects on the seismic response of concrete gravity dams

Abstract

<p>The behaviour of a concrete gravity dam-reservoir-foundation system is a very complex system to analyze. Currently, the length of the reservoir is assumed infinite during the seismic analysis and design of dam structures. Since many of the natural reservoir systems are finite, this assumption may significantly miscalculate the response of the dam monolith to earthquake ground motion. The objective of this research is to investigate the effect of a finite length upstream reservoir on the monolith's seismic response, including consideration of the reservoir's characteristics. This study is comprised of three main components. First, a closed form solution of the dam-reservoir problem is developed. The ground motion is assumed to only excite the dam monolith. Second, a detailed analysis procedure is used to investigate the response of the monolith when both the monolith and the reservoir's far boundary is excited. Lastly, a stress analysis is conducted to examine the effect of a finite length reservoir on the dynamic tensile stresses that are developed in the monolith. The finite length of the upstream reservoir was found to be a very important parameter in defining the response of the dam monolith to seismic input. The response of the dam-reservoir-foundation system was found to be significantly different when the reservoir's length was assumed to be finite than when it was assumed infinite. The ratio of the reservoir length to dam height (L/H), the reservoir-foundation interface, the monolith's elastic modulus, the phase of the ground motion between the monolith and the reservoir's far boundary, and the reservoir's far boundary have all been determined to be important aspects in defining the monolith's dynamic and seismic response.</p>