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Civil-Comp Proceedings
ISSN 1759-3433
CCP: 83
Edited by: B.H.V. Topping, G. Montero and R. Montenegro
Paper 163

Parametric Instability Analysis of Stringer Stiffened Circular Cylindrical Shells under Axial Compression and External Hydrostatic Pressure

M.R. Khedmati1, M.J. Mazaheri1 and A.R. Karimi2

1Faculty of Marine Technology, Amirkabir University of Technology, Tehran, Iran
2Mechanical Engineering Group, Institute for Technology Development, Tehran, Iran

Full Bibliographic Reference for this paper
M.R. Khedmati, M.J. Mazaheri, A.R. Karimi, "Parametric Instability Analysis of Stringer Stiffened Circular Cylindrical Shells under Axial Compression and External Hydrostatic Pressure", in B.H.V. Topping, G. Montero, R. Montenegro, (Editors), "Proceedings of the Eighth International Conference on Computational Structures Technology", Civil-Comp Press, Stirlingshire, UK, Paper 163, 2006. doi:10.4203/ccp.83.163
Keywords: instability, stringer stiffened shell, axial compression, hydrostatic pressure.

About three-fourths of the earth's surface is covered by water. It is believed that during the twenty-first century, the interest in exploring and using the ocean sea bed will increase, for both military and commercial purposes. Submarines and offshore structures comprising of shell structures stiffened with other structural elements, will be the first structures that are used for such purposes. In this context, a better understanding of the behaviour and strength of such a type of stiffened shell is of paramount importance.

Different methods may be applied in order to capture buckling behaviour and the strength of shell structures [2,3]. Analytical solutions [4] as well as numerical and experimental ones have already been developed for estimation of the buckling strength and behaviour of unstiffened and stiffened shells. Many years of designing and testing, ensure that submarines are not prone to buckling when subjected to high external underwater pressure. A balance is required between over designing to prevent buckling and avoiding a weight gain penalty. Finite element analyses assist in determining this balance by predicting if buckling will occur. Linear buckling analyses predict the critical modes of collapse. Non-linear load-displacement analyses predict collapse pressures for critical modes of collapse, taking into account plasticity and realistic imperfections formed during manufacturing processes. Non-linear analyses are required because failure can occur by buckling at pressures which may be considerably lower than those predicted by linear buckling analysis.

The focus of this study lies on the subject of buckling analysis of stiffened shells. In line with this research requirement, the commercial finite element code ANSYS [1] is utilised to simulate the collapse of stringer stiffened shells. Different parameters are considered in the finite element models.

ANSYS User's Manual (version 7.1), Swanson Analysis Systems Inc., Houston, 2003.
M.J. Mazaheri, "Elastic Buckling Analysis of Circular Stiffened Shells", MSc Thesis, Faculty of Marine Technology, Amirkabir University of Technology, Tehran, Iran, 2005.
C.P. Ellinas, W.J. Supple and A.C. Walker, "Buckling Of Offshore Structures: A State of the Art Review", Gulf Pub. Co., 1984.
S.P. Timoshenko and J.M. Gere, "Theory of Elastic Stability", McGraw-Hill Book Company Inc., 1961.

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