Investigating the Reservoir Sediment Effects on Seismic Damage of Concrete Gravity Dams Using Nonlinear Incremental Dynamic Analysis (NIDA)

The aim of this paper is to investigate the impact of reservoir sedimentation on the seismic damage of concrete gravity dams using nonlinear incremental dynamic analysis. The study involves subjecting the Koyna gravity dam to a set of 12 earthquakes, which are divided into three subsections: far-field, near-fault with a short period pulse, and near-fault with a long period pulse. Each earthquake is scaled to ten increasing intensity levels. The nonlinear seismic analysis of the concrete gravity dam-reservoir-sediment-foundation systems is based on the concrete damage plasticity (CDP) model, while the sediment material layer in the reservoir is assumed to be linear elastic. The study investigates the propagation of damage throughout the dam body and presents various incremental dynamic analysis (IDA) curves. Additionally, two different damage indices are proposed by comparing the response demands in seismic analysis with the determined structural capacities. Finally, the study develops seismic fragility curves using various limit-states of dam structures, considering sediment and without considering sediment in the reservoir. The study reports a slight impact of reservoir sedimentation on seismic damage levels and seismic fragility of gravity dams.