04.17: Cylindrical shell buckling under a hydraulic constraint: Numerical study

Abstract

Steel cylindrical shell structures are used in a large variety of civil engineering applications such as off-shore platforms, tanks, silos, wind turbine towers, etc. The local stability of such structures and their sensitivity to imperfections is a well-known problem. In current engineering practice the design method is based on the selection of an imperfection class for the shell and subsequently calculating a reduction factor,χ, to the resistance of the shell. One such methodology is supplied by the EN1993-1-6; special conditions are given to pressurized tubes subjected to meridional compression. Past studies have focused on the stability of cylindrical shells with internal pressure. The stability problem of a long cylinder considering the internal pressure as a simple static load was addressed. Thus, the approaches considered the fluid as compressible. The purpose of the present work is to investigate numerically the potential benefit of using an incompressible fluid fully enclosed in a circular cylindrical shell. The constraint imposed by the presence of the liquid in the interior of a shell will be referred to as "hydraulic constraint". As liquids are nearly incompressible, the buckling of a liquid-filled shell has to satisfy the condition that the integral of all the displacements normal to the shell surface is equal to the volume variation of the contained liquid. The volume variation of the shell interior has to be equal to the dilation of the shell due to liquid pressure increments associated to the onset of geometrical instability. Additionally, the weight of the contained liquid causes additional circumferential tension in the cases of vertically placed cylinders. The methodology followed is the numerical analysis of cylindrical shells by means of the ABAQUS Finite Element code and a comparison with the methods given in the Eurocode.