Seismic response of concrete gravity dams under near field and far field ground motions

Abstract

Near field ground motions trigger higher damage to the structures due to the presence of distinct velocity pulses which are absent in far field ground motions. The present study deals with the time history analysis of dam-reservoir-foundation coupled system using finite element technique under near field and far field ground motions. Koyna dam, which is a concrete gravity dam, is taken as case study for the present investigation. Six ground motions, recorded near to the ruptured fault are selected as near field ground motions. Whereas, six other ground motions, recorded at other stations located far away from fault plane, of the same earthquake events, are considered as far field ground motions. Along with the comparative study of seismic response of Koyna dam, qualitative assessment of the seismic performance of the dam are also evaluated. The results obtained from the analysis demonstrate the different impact of near field and far field ground motions on the seismic response of concrete gravity dams. Further, the study also ascertain the importance of selection of far field ground motions on seismic safety of concrete gravity dams.