Earthquake Resistant Design of Intake-Outlet Towers

The problem of designing reinforced concrete intake-outlet towers, partially submerged in water, to withstand earthquake ground motion is examined in general terms. It is shown that water, surrounding as well as inside, significantly affects the response to ground motion and these hydrodynamic effects should be considered in the design of towers. A rational method for elastic design including the hydrodynamic effects is proposed. It is recommended that towers be designed to elastically resist ground motions which they may experience several times during their useful life. The ductility requirements that would be imposed on code-designed towers by the intense ground motions expected near the causative fault during high magnitude earthquakes are evaluated; they appear to be rather large. It is recommended that forces for elastic design be increased so that the lateral displacement ductility requirements imposed by the most intense ground motion that can occur at the site would be no larger than a ductility factor of two.