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From:
Elisabeth Slettum (Faculty of Mathematics and Natural Sciences, University of Oslo),
“A Semi-Analytical Model for Buckling of Stiffened Cylindrical Shells”, Master’s degree thesis, June 2013, (Supervisor Associate Professor Lars Brubak)
SUMMARY: Cylindrical shells are common configurations within the technology. The transition from the side to the bottom on a ship has the shape of a fourth of a cylindrical shell. Both ring and stringer stiffeners can be added to the shell for support. Buckling of this type of structure is an important area of interest. The main purpose of this thesis has been to make a semi-analytical model that can describe how a ring stiffened shell and stringer stiffened shell re- spond during buckling. A variety of loads have been subjected to the shell model. Simple analytical expressions do not exist for clamped shells or shells subjected to shear and numerical methods must be used. The development of the model has been done by use of linear buckling theory and an energy method, the Rayleigh Ritz method. The model has been programmed in Fortran. Eigenvalues and associated eigenmodes have been found. The semi-analytical model has been verified against the finite element anal- ysis software Abaqus. The results from the models were in good agreement with each other. The apply of the semi-analytical model on a bilge struc- ture showed a deviation in the results. A small difference in the boundary conditions, with the element model being stiffer due to the edges being held straight, was causing the deviation. The difference in the results from the semi-analytical model and the element model was smaller for the ring stiff- ened shell than for the unstiffened shell and the stringer stiffened shell. The buckling load calculated by the semi-analytical model were on the conserva- tive side compared with the element model.
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