Structural failure of non-uniform, infinitely long cylindrical shells subjected to uniform external pressure

This thesis presents analytical and finite element solutions for elastic buckling, elastic-plastic collapse and buckle propagation of a non-uniform, infinitely long cylindrical shell subjected to uniform external pressure. The results presented herein can be used to analyze structural collapse of a corroded pipeline, which can be modeled as an infinitely long cylindrical shell with two sections: one of nominal thickness and the other of reduced thickness. Symmetric and anti-symmetric buckling modes were found to occur depending on the relative thickness of the two different regions and the angular extent of the section with the reduced thickness. Snap-through and global buckling of the cylinder were also distinguished. Using the collapse modes from the elastic buckling analysis, one can obtain solutions for buckle propagation pressure of corroded pipelines from rigid-plastic analysis and Maxwell's theorem of co-existent phases. A parametric study shows how the elastic buckling and buckle propagation pressures decrease when either the relative thickness or the angular extent of the section with the reduced thickness increases. Finite element solutions for elastic buckling and buckle propagation were also found using ABAQUS and the analytical solutions were found to be less than 5% and 15% with finite element predictions, respectively.