Keywords: shell structure, liquid-containment structure, tank, shell analysis, shell design.

Shell structures find application in many fields, and fulfil various functions, including liquid containment [1, 2]. Shells are widely used throughout the world for holding water in the form of elevated concrete tanks for urban communities. In industry, applications include storage vessels for the containment of petroleum products, chemicals, and liquefied gases. While the advantage of thin shells as a form of construction are well-known (high strength-to-weight ratio, savings in material usage, excellent aesthetics, etc.), the main challenge has always been in understanding the mechanics of the shell in order to improve design practice.

In this paper, we review recent progress in the understanding of the strength, stability, and vibration behaviour of liquid-containment shell structures, and how this has influenced design practice. The survey is limited to work published since the year 2000. Investigations on containment metal shells (typically steel tanks and silos) have mostly been concerned with cylindrical and conical geometries, which are the most common in practice owing to the ease of fabrication of shells of single curvature. Not many studies have been found on metal shells of double curvature, which include spherical, ellipsoidal and toroidal vessels. Elevated concrete water tanks can be constructed in a great variety of interesting shapes, owing to the mouldability of concrete into any desired shape, but, surprisingly, not much exploration of new shell forms for concrete tanks has been undertaken in recent times. A relatively recent innovation is the adoption of egg-shaped concrete shells as sludge digesters, and a number of studies have been undertaken in the past 10 years to extend the possibilities [3-5].

Various investigations have sought a better understanding of the linear and non-linear response of shells to a variety of loading and environmental conditions, including hydrostatic, hydrodynamic, wind, seismic, support-settlement, impact, blast and thermal effects. This increased understanding has had a direct impact on the way liquid-containment shell structures are designed, as reflected in current design standards. It is concluded that analytical, numerical and experimental investigations all still have a part to play in giving a more complete understanding of the mechanics of the problems, and hence more reliable criteria for design.

[1]

W. Flugge, "Stresses in Shells", Springer-Verlag, Berlin, Germany, 1973.

[2]

A. Zingoni, "Shell Structures in Civil and Mechanical Engineering: Theory and Closed-Form Analytical Solutions", Thomas Telford, London, United Kingdom, 1997.

[3]

A. Zingoni, "Stresses and deformations in egg-shaped sludge digesters: Membrane effects", Engineering Structures, 23, 1365-1372, 2001. doi:10.1016/S0141-0296(01)00055-4

[4]

A. Zingoni, "Stresses and deformations in egg-shaped sludge digesters: Discontinuity effects", Engineering Structures, 23, 1373-1382, 2001. doi:10.1016/S0141-0296(01)00056-6

[5]

A. Zingoni, "Parametric stress distribution in shell-of-revolution sludge digesters of parabolic ogival form", Thin-Walled Structures, 40, 691-702, 2002. doi:10.1016/S0263-8231(02)00020-4

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