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Date of Award

7-1997

Degree Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Civil Engineering

Supervisor

A. Ghobarah

Abstract

A study was conducted to investigate the dam-reservoir interaction effect on the linear and nonlinear seismic response of concrete gravity dams. A mathematical approach was developed for the solution of the coupled dam-reservoir interaction problem which can be implemented in the nonlinear seismic analysis of concrete gravity dams. Two methods of staggered solution procedures are proposed for the dam-reservoir interaction. Using Routh-Hurwitz criteria, both methods are shown to be unconditionally stable when the two differential equations of the fluid and structure include damping terms. The staggered pressure method was modified for use when the equation of motion includes a lumped (diagonal) mass matrix. A finite element program was developed to include the staggered solution schemes for seismic analysis of concrete gravity dams. The program considers the dam-reservoir interaction. The reservoir can be considered as infinite in which an appropriate boundary condition can be applied at the desired distance from the upstream face of the dam. The finite reservoir condition is also an option that can be included in the analysis. The effect of the travelling wave where nonuniform earthquake ground motion is applied to the boundary of the reservoir can be evaluated. The nonlinear analysis of the concrete gravity dam was considered based on nonlinear fracture mechanics crack propagation criterion. Seismic response of a concrete gravity dam subjected to travelling seismic excitation is investigated. The analysis is applied to the case of a gravity dam with infinite and finite reservoirs of different lengths to evaluate the effect of the travelling seismic wave on the dam crest displacement. Various wave speeds representing the speed of wave travel in the reservoir foundation, are used in the analysis. Earthquake waves are considered to travel in the upstream or the downstream directions. The nonlinear seismic fracture response of the Pine Flat dam is investigated under the effect of reservoir interaction. Smeared crack analysis model based on a nonlinear fracture mechanics crack propagation criterion was used to study the cracking behaviour of a concrete gravity dam. The staggered method is used to solve the dam-reservoir interaction problem and results of the analysis were compared with the case when the added mass was used to represent the interaction effects. An experimental program was conducted on small scale models of the concrete dam. A loading mechanism with two actuators was designed to apply four concentrated loads on the upstream face of the dam model. Dynamic load was applied cyclically by an actuator to represent the effects of the earthquake loadings. The static load which represent the hydrostatic pressure was kept constant. The material properties of the model was maintained the same as the prototype. In the proposed approach, the stress distribution at the top part of the dam model and prototype of the same material properties are found to be in close agreement.

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