Hydrodynamic Pressures on Dams During Earthquakes

The intensity, distribution, and frequency characteristics of hydrodynamic pressures acting on dams during earthquakes are discussed. A short review of previous work on this subject is presented, with particular emphasis on evaluation of common simplifying assumptions. Including compressibility of water, an analysis is made of the pressures generated on a rigid dam with a vertical upstream face. These results are intended for gravity dams. General expressions for the complete time history of pressures during arbitrary horizontal and vertical ground motions are derived. It is concluded that the concept of an added mass, moving with the dam, to represent hydrodynamic effects is not valid for earthquake-type excitations. It is also shown that significant errors are introduced by ignoring compressibility of water. The standard design practice in considering additional water pressures on dams due to earthquakes is compared with the theoretical responses.