Dynamic Response of Dam–Reservoir–Foundation Systems Subjected to Asynchronous Ground Motion

This work aims to determine the dynamic response of dam–reservoir–foundation systems subjected to asynchronous ground motion. To this end, two-dimensional variable-noded solid and fluid finite elements based on a Lagrangian approach were implemented as subroutines in Fortran 77. These subroutines were incorporated into the program MULSAP, which performs asynchronous dynamic analyses of structural systems; MULSAP, extended for fluid–solid systems, was used to model dam–reservoir–foundation interactions. For comparison, the subroutines were also integrated into SAP IV to perform classical (synchronous) dynamic analyses and to examine the infinite-velocity case. This PhD study comprises five chapters. Chapter 1 introduces the problem, reviews previous work on uniform and asynchronous ground motion effects on dams, and defines the scope of the research. Chapter 2 derives the basic displacement-based (Lagrangian) relations for fluid behavior and, using these relations, develops the finite element formulation for fluid systems; it then presents the dynamic formulation for coupled fluid–solid systems under asynchronous ground motion. Compressibility of the fluid and free-surface sloshing motions are included in the fluid formulations. Chapter 3 describes baseline correction and integration procedures for strong-motion acceleration records and presents numerical applications using various recorded accelerograms. Chapter 4 applies the formulations of Chapter 2 to a sample concrete gravity dam. Using the dam data, modal analyses and asynchronous dynamic analyses were performed for several wave-propagation velocities. In the modal analysis section, Eulerian and Lagrangian solutions, MULSAP and SAP IV results, foundation models with and without mass, and full/empty reservoir conditions are compared; the first 30 mode shapes of the coupled system are also presented. In the asynchronous dynamic analysis section, horizontal and vertical ground displacement shape vectors (r-vectors) are computed. MULSAP results for the infinite-velocity case are compared with SAP IV results, and the effects of asynchronous horizontal and vertical ground motion on the frequency content, stress amplitudes, and hydrodynamic pressures are investigated. The impacts of ground displacement, reservoir presence, and foundation mass on the response are also examined. Chapter 5 summarizes the conclusions and provides detailed recommendations based on the study.