Modern analysis of axisymmetric shells
File(s)
Author(s)
Filippidis, Achilleas
Type
Thesis
Abstract
The load-carrying capacity of thin axisymmetric shell structures is often governed by their buckling resistance, characterised by a harmonic distribution of the modal displacement field along the shell’s circumference. Despite the widespread use of commercial finite element software, the mathematical framework required for this classical stability problem is largely absent. To address this, a computational tool has been developed that tackles the inherently two-dimensional shell buckling problem on its mathematical basis, promoting the need for specialised formulations within general finite element environments and providing an open-source alternative to black-box commercial solvers. The software aligns with the EN 1993-1-6 taxonomy for shell structure design, enabling characterisation of reference systems through the capacity curve framework.
Using this tool, justification is provided for a recent amendment in the second generation of EN 1993-1-6, which concerns the assumption that the capacity curve for cylinders under meridional compression is the most conservative among reference axisymmetric shell systems. Comparative studies of cylinders under meridional compression and global bending reveal that the current provisions of the European Standard may overestimate characteristic resistance, potentially leading to unsafe designs. A detailed documentation of the sensitivity demonstrated by otherwise well-established general purpose computational software to initial modelling conditions relating to discretisation and incrementation parameters is provided as a by-product of this numerical investigation.
An analytical study of shear-flexible cylinders is also presented to establish reference solutions for the stability of thick cylinders under meridional compression and external pressure. These closed-form solutions serve as benchmarks for developing a finite-thickness two-node element for non-symmetric bifurcation buckling analysis. Finally, geometric nonlinearities are examined in meridionally compressed cylinders to identify sources of geometric stiffening behaviour and the challenges in consistently modelling nonlinear axisymmetric shell response across varying slendernesses.
Using this tool, justification is provided for a recent amendment in the second generation of EN 1993-1-6, which concerns the assumption that the capacity curve for cylinders under meridional compression is the most conservative among reference axisymmetric shell systems. Comparative studies of cylinders under meridional compression and global bending reveal that the current provisions of the European Standard may overestimate characteristic resistance, potentially leading to unsafe designs. A detailed documentation of the sensitivity demonstrated by otherwise well-established general purpose computational software to initial modelling conditions relating to discretisation and incrementation parameters is provided as a by-product of this numerical investigation.
An analytical study of shear-flexible cylinders is also presented to establish reference solutions for the stability of thick cylinders under meridional compression and external pressure. These closed-form solutions serve as benchmarks for developing a finite-thickness two-node element for non-symmetric bifurcation buckling analysis. Finally, geometric nonlinearities are examined in meridionally compressed cylinders to identify sources of geometric stiffening behaviour and the challenges in consistently modelling nonlinear axisymmetric shell response across varying slendernesses.
Version
Open Access
Date Issued
2026-06-29
Date Awarded
01/11/2025
License URL
Advisor
Sadowski, Adam J.
Publisher Department
Department of Civil and Environmental Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)