Role of strong motion duration on seismic responses of high concrete faced rockfill dams

This study investigates the role of strong seismic motions on the dynamic responses of high CFRDs through elastoplastic analysis. Damage measures (DMs) including vertical and horizontal displacements, plastic shear strain, as well as a face-slab damage index are selected to gauge the deformation, stability of the dam slope and the anti-seepage ability of the face slab, respectively. The selected DMs are key to the safety of high CFRDs. A group of 35 as-recorded ground motions with a wide range of durations are modified to conform to a 5% damped target spectrum are used as input motions for dynamic analysis. A comprehensive understanding of the effects of ground motion duration is obtained through a tri-fold analysis of the ground motion records, the nonlinear dynamic response of CFRDs and the statistics of the results. The definitions of significant duration, bracketed duration and uniform duration, each with consideration to two different thresholds, are selected to characterize strong motion durations. The results suggests that significant duration is the most useful indicator for seismic assessment of high CFRDs and for evaluating the effects of the duration of an earthquake on the integrity of high CFRDs.