Application of the endurance time method in seismic analysis of concrete gravity dams

In this paper, application of the Endurance Time (ET) method in seismic analysis of concrete gravity dams has been investigated. The ET method is based on time history analysis of structures, subjected to specially designed intensifying acceleration functions. It is expected that by developing its application in analysis of concrete dams, useful information on the seismic behavior of such dams at various excitation intensities can be obtained. Results from linear analysis of Folsom and Koyna dams under real earthquakes and ET acceleration functions have been compared. It is shown that the ET method can predict the response of concrete gravity dams to individual earthquakes with reasonable accuracy in linear analysis. In order to evaluate concrete gravity dams by linear analysis, the target time has been assumed to correspond to the OBE level of earthquake. Endurance criteria can be set as the time when the desired damage index(es), e.g. maximum principal stress, reaches its allowable value. The design can be considered satisfactory if endurance time is more than target time and vice versa. Also, potential application of the ET method in non-linear analysis of concrete gravity dams has been investigated. It is shown that crack profiles during earthquakes could be traced by the ET method.