Theme A: Three-dimensional Seismic Analysis of Tsankov Kamak Dam (double curvature concrete arch dam). Formulation and synthesis of the results

Abstract ICOLD Committee on Computational Aspects of Analysis and Design of Dams organized the 17 th ICOLD Benchmark Workshop on Numerical Analysis of Dams in Sofia, Bulgaria, in April 2025. Theme A concerns the modelling of the static and seismic behaviour of a large concrete double curvature arch dam ideally inspired to Tsankov Kamak Dam. The study proposed in the Theme A is intended to continue and improve the work carried out in previous Benchmark Workshops focused on seismic analyses. The most recent investigation on this topic was proposed in Theme A of the 15 th ICOLD Benchmark Workshop in Milan, Italy (2019), titled “Seismic Analysis of Pine Flat Concrete Dam”: it was a 2D structural problem where the simple geometry was specifically chosen with the objective to facilitate the adoption of advanced methods able to consider the semi-unbounded size of the foundation and the dynamic interactions of the dam with the foundation and the reservoir. In the present study, to accurately define the structural response of the concrete arch dam, it is necessary to consider the three-dimensionality of the problem and the non-linear behaviour of the system. In the case of the 3D modelling of arch dams, the foundation cannot be idealized with a flat box model (semi-unbounded half-space), but the presence of the canyon must be conveniently considered; in addition, the vertical joints greatly influence the behaviour of these structures. Theme A included six case studies, each featuring one or more tasks, with certain tasks designated as mandatory and others as optional. Twelve teams, representing eleven countries, submitted solutions. The comprehensive synthesis of the main outcomes of Theme A provides significant contribution to the seismic analysis of arch dams subjected to earthquakes capable of triggering the non-linear structural behaviour, summarizing the most recent methods for carrying out such analyses, and offers important insights for interpreting and understanding their results.