Integrated duration effects on seismic performance of concrete gravity dams using linear and nonlinear evaluation methods

Abstract

For the assessment of seismic performance of concrete gravity dams, ground motions with horizontal and vertical components are usually selected as seismic excitations. Although various definitions have been proposed to compute strong motion duration from a single component (either horizontal or vertical one) of seismic excitations, duration definitions accounting for the contributions of all components of seismic excitations are still lacking. In order to bridge the gap between duration definitions and multi-component seismic excitations used for simulation, a concept of integrated duration is proposed in this contribution. With the definition of integrated duration, a unified strong motion duration can be calculated for a seismic excitation with multiple components, which facilitates the quantitative evaluation of duration effects. To examine the influence of integrated duration on the seismic performance of concrete gravity dams, both the linear and nonlinear evaluation methods considering the dam-reservoir-foundation interaction are adopted in this study. The linear evaluation method is based on demand capacity ratio, cumulative overstress duration and spatial extent of overstressed regions, whereas the nonlinear seismic analysis of concrete gravity dam-water-foundation systems is on the basis of a Concrete Damaged Plasticity model. 20 real earthquake records with a broad range of durations are selected as seismic excitations to quantify the correlation between the proposed integrated duration and the seismic performance of concrete gravity dams. It is found that the cumulative overstress duration, the accumulative damage and the residual plastic deformation are strongly affected by the integrated duration. Apart from the integrated duration effects, the influence of the vertical component of ground motions is also discussed.