Response spectrum and modal dynamic analyses of gravity dams using ground motion accelerations modified to account for hydrodynamic effects

Abstract

This research proposes simplified methods for response spectrum and modal dynamic analyses of gravity dams using time-history and spectral seismic accelerations modified to directly account for hydrodynamic effects. The developed methods waive the need for specialized fluid-structure interaction software. They also lead to more accurate assessment of coupled structural flexibility and hydrodynamic effects due to each vibration mode than the static correction method commonly used in traditional simplified methods. The methodology utilizes analytical formulations of hydrodynamic pressure or simplified added masses to obtain the contributions of the selected vibration modes to the total seismic response. A hydrodynamic modification factor characterizing the amplification/de-amplification of acceleration seismic demands due to earthquake-induced hydrodynamic effects is also introduced. The application of the proposed methods is illustrated numerically through examples of two typical gravity dam-reservoir systems subjected to four earthquakes. The obtained results are in excellent agreement with the classical reference solutions. Time-history and spectral seismic acceleration demands modified by hydrodynamic effects as well as selected key response indicators, such as relative displacements and stresses within the studied gravity dams, are discussed.