Abstract:
This study investigates the nonlinear seismic response of Morrow Point Dam using advanced finite element analysis tools to evaluate the structural behavior of a highly segmented thin-arch concrete dam subjected to strong ground motions. The work was conducted to support the U.S. Bureau of Reclamation’s Dam Safety Program and to improve computational methods for predicting dam performance during earthquakes. Multiple finite element models of varying complexity were developed, incorporating features such as contraction joints, shear key geometry, flexible foundations, topographically accurate geology, hydrodynamic reservoir interaction, abutment wedge modeling, and material nonlinearities due to concrete cracking. The methodology combined NIKE3D implicit simulations for static initialization and DYNA3D explicit analyses for dynamic seismic loading, allowing evaluation of joint opening, displacement response, stress distribution, and stability. Parametric studies compared the influence of base accelerations versus force time histories, reflective versus non-reflective boundaries, Westergaard added mass versus explicit water modeling, and tied versus sliding contact surfaces. Results demonstrated the importance of deconvolving input motions to the foundation, using transmitting boundary conditions, and accurately representing contraction joint behavior. The peak predicted upstream-downstream displacement was approximately 2.86 inches, consistent with earlier Bureau analyses, and the dam remained structurally stable throughout the simulated seismic events. The findings underscore the essential role of finite element analysis in quantifying seismic risk, validating design assumptions, and informing dam safety evaluations under extreme earthquake loading.
