Résumé
The present article focuses on the three-dimensional seismic analysis of an arch dam inspired by the case of Tsankov Kamak Dam, a double curvature arch dam, as part of Theme A of the 17th ICOLD Benchmark Workshop (BW) on the Numerical Analysis of Dams. The objective is to compare different numerical approaches for assessing the seismic behaviour of the dam and the dam-reservoir-foundation interactions. The study employs FLAC3D for the static and time-history analyses, and Ansys Workbench for modal analyses. Various modelling complexities are explored, including massed and massless foundations, dam-bedrock interfaces, vertical joints interfaces, and nonlinear concrete behaviour using both Concrete Damage Plasticity and Mohr-Tension constitutive models. Results demonstrate the sensitivity of the dam’s response to these modelling choices, particularly regarding stress distribution, displacements and amplification of accelerations. When comparing massed to massless foundation models, it is confirmed that an additional damping is obtained when considering massed foundation with radiative boundary, although it is lower compared to usual values reached with gravity dams. The evolution of the results considering increasing complexity for the massed foundation models follows expectations: when considering dam-foundation interfaces the dam heel tensile stresses are released, increasing displacements and the tensile stresses downstream; the concrete non-linear models allow to estimate the crack extension at the downstream face, which are rather of limited extent since the stresses in the elastic concrete model are only 10% higher than the concrete tensile strength. The behaviour depicted with the Concrete Damage Plasticity model appears exaggerated given the low earthquake load case. This is further confirmed by scaling up the earthquake load. The Mohr-Tension law appears to be a simpler and practicable alternative which leads to more a realistic behaviour.