Assessment of current design procedures for conical tanks under seismic loading

Abstract

This study is motivated by the fact that no design provisions currently exist specifically for conical tanks under seismic excitations. The design of liquid storage structures is governed by the American Water Works Association (AWWA), American Petroleum Institute (API), or Eurocode 8. An approximate method based on replacing the conical tank with an equivalent cylinder is given in these design codes. The state of stresses in conical tanks is different than that of cylindrical tanks. A previously established equivalent mechanical model is used to determine the response of a number of conical tanks under horizontal excitations. The models incorporate the different components of the hydrodynamic pressure and account for flexibility of the tank walls. Using an assortment of seismic hazard areas, the maximum base shear force and overturning moment are evaluated for a number of conical tanks. Those are compared to the corresponding values predicted by the design codes using the equivalent cylinder approach. The results reveal that this approximate approach is not adequate for designing conical tanks to resist seismic excitations.