Non-linear seismic analysis of arch dams considering joint movements and a concrete damage model

Abstract

This paper presents a study on the non-linear seismic response of Cabril arch dam (Portugal), for a load combination including the dam’s self-weight, the hydrostatic pressure (full reservoir) and the seismic loading (10 s generated accelerograms) applied at the dam base. The main results are presented considering two accelerograms, with peak ground accelerations of 0.2g and 0.6g. The investigation is focused on the effects of the non-linear behaviour of joints on the structural response of an arch dam under stronger earthquakes and on the resulting concrete damage distributions. The numerical simulations are performed using DamDySSA4.0, a 3D finite element program developed in LNEC for dynamic analysis of concrete dams, including a recently developed module for non-linear seismic analysis. The dynamic behaviour of the dam-reservoir-foundation system is simulated using a coupled model in displacements and pressures, considering the dam-water interaction and non-proportional damping, and using a sub-structuring technique to simulate the foundation. The non-linear seismic response is computed using a time-stepping algorithm, based on the Newmark method, and the stress-transfer method. The non-linear behaviour of concrete is considered using an isotropic damage model with softening and two independent damage variables (d+ for tension and d- for compression), and the opening/closing/sliding movements of joints are simulated using joint finite elements and the classic Mohr-Coulomb law, for vertical contraction joints, dam-foundation interface and existing cracks. The aim is to summarise the implemented formulations and show the potential of DamDySSA4.0 for predicting the non-linear seismic behaviour of concrete dams and to support seismic safety verifications.