Statistical investigation of the influence of ground motion duration on concrete gravity dam responses by proposing a quantitative index

Abstract

This study aims to investigate the influence of ground motion duration on the seismic performance of concrete gravity dams seeking a quantitative correlation between ground motion durations and structural responses at several seismic intensity levels. In this regard, the Koyna gravity dam, located in India, is selected as the case study. In order to analyze the cumulative damage of the dam body, incremental dynamic analysis with 30 earthquake records with a broad range of durations has been implemented. All selected ground motion records have been spectrally matched to a target spectrum to isolate the contribution of duration from the effects of other ground motion parameters. The first mode spectral acceleration of the structure is considered the intensity measure, and the relative crest displacement and damage dissipation energy are chosen as the damage measure in this paper. Unlike previous studies in this field which are based on central measures of responses such as absolute mean value, in this study confidence intervals of the mean value of responses have been calculated in order to reach a quantitative relationship considering the uncertainty of results. Also, a duration influence index is developed. The obtained results revealed that there is a positive correlation between the ground motion duration and the cumulative damage of the concrete gravity dams so that long-duration motions can cause about 25% higher responses in relative crest displacement and about 70% higher responses in damage dissipation energy in comparison to short-duration ground motions at the same intensity.