Electronic Thesis and Dissertation Repository


Doctor of Philosophy


Civil and Environmental Engineering


Ashraf El Damatty


Steel conical tanks are widely used for liquid storage in North America and elsewhere. A number of those tanks collapsed in the last decades as a result of instability of the steel shells. Despite being widely used, no specific design procedure is available for conical tanks under dynamic conditions. The research conducted in the current thesis presents a simplified approach for the design of steel conical tanks when subjected to ground excitations in the form of horizontal and vertical excitations.

First, the capacity of steel conical tanks to avoid yielding and buckling of the tank vessel under hydrodynamic pressure resulting from horizontal ground excitation is evaluated using non-linear static pushover analysis. The capacity of steel conical tanks under hydrodynamic pressure resulting from vertical ground excitation is then evaluated using the same procedure. The analyses are conducted numerically using a non-linear finite element model that accounts for the effects of large deformations and geometric imperfections on the stability of steel conical tanks. Based on the obtained capacities, a design approach is proposed which is based on satisfying an interaction formula that avoids both yielding and buckling of the tank vessel. This formula is a function of the steel conical tank capacities and the seismic demands resulting from hydrodynamic pressure including both impulsive and sloshing components. Finally, this design approach is validated through comparison with the results of non-linear dynamic analysis.

The effect of the base rocking motion on the seismic behaviour of conical shaped steel tanks is then studied and a mechanical analog that simulates the forces acting on a conical tank subjected to a horizontal excitation including the effect of this base rocking motion is developed. This mechanical model takes the flexibility of the tank walls into consideration as well the hydrodynamic pressure acting on the tank base.