A study on effects of initial deflection on ultimate strength of ring-stiffened cylindrical structure under external hydrostatic pressure

In this paper, design formulae of local and global mode ultimate strength currently available are reviewed and evaluated based on the results of finite element analysis, considering their capabilities of accounting for effects of initial hull deflection and variation of hull thickness. As initial hull imperfection data, actual imperfections measured from two small-sized and a mid-sized test models are used. Strain data measured from the test model are discussed and compared with the results of the finite element analysis. Collapse pressures calculated from FEA are compared with those estimated from the ultimate, strength design formulae for cylindrical shells. Effects of the initial imperfection on the collapse pressure of stiffened cylindrical shells are also investigated.