Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Civil and Environmental Engineering

Supervisor

Ashraf El Damatty

Abstract

Conical liquid storage tanks are widely used to store different liquids and to provide water supply at cities and municipalities. However, no comprehensive guidelines currently exist in the codes of practice for the structural analysis and design of such tanks. The walls of a conical tank can be made of steel, reinforced concrete, or a combination of the two materials in a composite type of construction in which steel and concrete walls are connected using steel studs. The research conducted in this thesis provides a comprehensive understanding of the structural behaviour of reinforced concrete and composite conical tanks under hydrostatic and seismic loadings. Finite element models for both reinforced concrete and composite tanks are developed and validated. In these models, a 3-D consistent shell element that accounts for the material nonlinear effect is used. The composite model also includes a 3-D contact element simulating the steel studs. The numerical models are utilized to study different behavioural aspects of reinforced concrete and composite conical tanks. An Equivalent Cylinder Method (ECM) is introduced and assessed for the analysis and design of reinforced concrete conical tanks. A set of charts that can be used to determine the adequate thickness and the straining actions for reinforced concrete conical tanks under hydrostatic pressure is developed. An Equivalent Section Method (ESM) for the analysis of composite tanks, which is based on using an equivalent single wall, is introduced and assessed. Both the ECM and ESM are found to be inadequate for the analysis of reinforced concrete and composite conical tanks, respectively. The composite finite element model is extended to include an optimization routine for minimization of the cost of composite conical tanks. The optimization of the design of a real composite conical tank using the developed scheme resulted in a reduction of 32% in the material cost. The study is proceeded by examining the seismic behaviour of composite conical tanks. This is done by extending a previously developed numerical model that takes into account the fluid-structure interaction that occurs during the seismic vibration of a conical tank. A simplified procedure for the analysis of composite conical tanks under seismic loadings is introduced. The procedure is found to be adequate for preliminary design as the differences in the prediction of the natural frequencies and seismic forces are shown to be less than 17% compared to those predicted by the sophisticated numerical model.

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