A novel variability evaluation framework of seismic response for arch dams considering the influence of distribution modes of conditional spectra

This study aims to propose a novel method for selecting as-recorded near-fault (NF) impulsive ground motion based on the idea of “wavelet multiscale decomposition-matching target conditional spectrum (CS)”, and then study the influence of different distribution modes of target CS (corresponding to different record selection strategies) on the dispersion and bias of dynamic response of arch dams. First, the representative measured NF pulse-like earthquakes are decomposed into high-frequency non-pulse ground motions using wavelet multiscale decomposition techniques to match the different distribution modes of the target CS (conditional mean spectrum (CMS) plus and minus several times the standard deviation response spectrum). The different distribution modes of the CS reflect the statistical response spectra of different discrete degrees, which may reflect the uncertainty in choosing realistic ground motion. The nonlinear damage and cracking model of high arch dam-reservoir water-foundation system is used to analyze the response characteristics of the dam, and the key influencing factors, such as different distribution modes of the target CS and pulse characteristics, are considered. The dispersion and bias of the dam response index are evaluated by investigating the statistical distribution of each response index under different CS distribution modes. The results show that adjusting the distribution mode of the target CS may significantly affect the dispersion and bias of the structural response results of arch dams. When the distribution mode of the target CS changes, the scatter of the side joint opening (joint No. 1) is the smallest, and the bias variation range of the overall damage volume ratio is the largest. The scatter and bias of the response indices of pulsed motion are larger than those of non-pulsed motion. Therefore, when investigating the variability of arch dam dynamic response, the influence of NF pulse-type seismic motion and pre-selected target spectrum distribution mode cannot be ignored.