Abstract:
This paper outlines the Bureau of Reclamation's methodology for performing complex nonlinear static and seismic structural analyses of concrete arch dams using explicit finite element techniques, specifically with the software
LS-DYNA for analysis and TRUEGRID for model geometry creation. The methodology is demonstrated through two case studies: a 500-foot-high thick arch dam (Hungry Horse Dam) and a 260-foot-high thin arch dam. The finite element model for the thick arch dam is highly detailed, featuring 160,000 nodes, 26 contraction joints, and a potentially movable foundation block. To accurately simulate real-world conditions, the reservoir is modeled with fluid finite elements to capture hydrostatic and hydrodynamic interactions; contact surfaces capable of sliding and opening are used for contraction joints and foundation discontinuities; and non-reflecting boundaries are applied at the foundation and reservoir extents. Deconvolved ground motions are applied at depth to propagate up through the foundation, creating spatially varying input for the dam. The model for the thin arch dam is even larger, with over 400,000 nodes, and uniquely includes an older 210-foot-high arch dam located just 7 feet upstream, as well as seasonal thermal loads. A significant effort was dedicated to model calibration and verification, where material properties derived from laboratory tests were refined by matching the model's calculated natural frequencies with measured values from forced and ambient vibration testing.
