Seismic Response Analysis of Concrete Gravity Dam under Near-Fault Velocity Pulse-Like Ground Motions

Abstract

The original single component of seismic data served as the foundation for the majority of previous investigations on the impact of pulse-like ground motion on the dynamic response of structures. The seismic responses of significant infrastructure are less studied when multicomponent motion is taken into account as seismic excitation. As velocity pulses may cause considerable damage to long-period structures, it is of great significance to understand the seismic responses of gravity dams under near-fault pulse-like ground motions for mitigating structural damage. In this study, a unique evaluation approach is suggested for examining the dynamic responses of gravity dams using the combined ground motion of the horizontal and vertical components. Furthermore, the seismic responses of the dam body under rotated and scaled multipulse excitations are investigated. We employed continuous wavelet transform to choose 16 near-fault pulse-like ground motions from actual seismic events with similar amplitude as seismic excitation signals in order to simulate the earthquake damage to the Koyna Dam using the finite-element approach. The displacement, principal stress, and damage fractures of the gravity dam are used to quantify the impact of the pulse intensity variation. The analysis results demonstrate that the structure has remarkable seismic response owing to the presence of large pulse records. The large residual and peak displacements are mainly caused by the velocity pulses and the sensitivity of the upper part of the dam neck to the horizontal relative displacement is significantly higher than that of the lower part. Although the mean intensity parameter of the rotated records with velocity pulse is smaller than that of the Koyna nonpulse, the former increases the mean damage to the dam by 41%. Compared with the rotated records, the scaled records may overestimate the damage of pulse-like motions to the structure, and the stronger pulses are likely to cause severe penetration cracks around the dam neck. The seismic response spectra reveal the potential effects of multicomponent pulse-like motions on the gravity dam and emphasize the significance of considering the combined motion for seismic design.