The Use of Discrete Element Models for the Seismic Assessment of Concrete Gravity Dams

Abstract

The assessment of the seismic performance of gravity dams is a difficult engineering problem requiring consideration of the cracking in a brittle medium as well as the interaction of the reservoir and the massive concrete structure. The problem is challenging from a practical point of view as well; a clear-cut damage indicator for assessing the performance of these systems is not present. The generally used finite element method (FEM)/rotating crack combination led to the utilization of indirect global demand parameters like crest displacements or damaged area ratios as damage indicators. While very robust in terms of the solution, the aforementioned combination leads to highly diffused crack patterns for large shaking, limiting the interpretation of the results for these systems on which discrete cracks' extent and widths are the primary damage measures. This limitation can be overcome by utilizing methods that simulate the discrete fracture phenomenon; in this study, the nonlinear seismic behavior of a concrete gravity dam-reservoir system was investigated using the developed discrete element framework, the modified applied element method (MAEM). Using incremental dynamic analysis, the cracking on the dam body was compared with those of the FEM qualitatively first, followed by a quantitative comparison focused on the propagation of the cracking using fragility curves. Then, the use of crack widths as a damage indicator was utilized, and model outcomes were compared. The utilized model reduced the diffusion of cracking commonly observed in FEM models using total strain smeared crack formulation and predicted more adverse behavior in terms of total crack widths and crack propagation.