Overview
ABSTRACT
Safely calculating the buckling resistance of steel shell structures requires the designer to understand several complex phenomena. The behavior of the shell before, during and after buckling depends largely on the geometry, the sensitivity to geometric and structural imperfections, loading mode and boundary conditions. The study of the stability of shells is thus a particularly challenging aspect of structural mechanics. Shells differ totally from other structural shapes in that the structure buckling resistance observed in experiments is often far below the buckling load calculated by a simple stability theory (linear eigenvalue analysis). The cause of this significant disparity and how this divergence is treated in calculations is explained. This article provides but a brief description of the buckling of shells therefore a more comprehensive study of this specialized literature is necessary in order to accurately evaluate the buckling resistance of a shell.
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Read the articleAUTHORS
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Guy LAGAE: Docteur-ingénieur – Professor at Ghent University - Structural Models Research Laboratory, Ghent University
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Wesley VANLAERE: Doctor-engineer – Research officer, Scientific Research Fund – Flanders (FWO) - Structural Models Research Laboratory, Ghent University
INTRODUCTION
A hull subjected to compressive stress is likely to bend transversely when the stress reaches a critical value: this phenomenon is known as "buckling". Buckling is a sudden deformation of the hull, generally exhibiting a number of waves in the circumferential and meridional directions. Since the loading is generally due to the weight carried by the hull, buckling will, in most cases, cause a sudden and total collapse. Hull shear generates principal compressive stresses and can therefore also cause instability when this shear reaches a critical threshold.
The load-bearing capacity of a hull is strongly influenced by geometric imperfections, which play an extremely unfavorable role. Buckling resistance is also governed by the material's yield strength. Determining the load-bearing capacity of hulls by analytical methods is only possible for hulls that are simple in geometry and loading.
The development of high-performance computers and highly efficient numerical methods now make it possible to calculate a shell structure, whatever the complexity of the geometry, the importance of the effect of imperfections and non-linear behavior. These numerical models are used not only by scientific researchers, but also – in the form of commercial FEM (Finite Element Method) software – by project engineers.
Today, more than ever, the project designer's main task is to correctly model and convert the numerical results into the characteristic buckling resistance of a "real" hull, in order to achieve a reliable and cost-effective project.
This dossier briefly discusses calculation methods for verifying a hull's resistance to buckling.
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