抄録
General instability is one of the most important subjects of cylindrical shells reinforced by ring stiffeners under uniform pressure. Recently, based on the application of nonlinear analysis using the finite element method, and more reliable collapse tests using models manufactured with high fabrication technique and of uniform material characteristics, the study to review the design procedure, which were based on the experimental works of collapse tests using a number of scale models, has been carried out.
Since pressure hulls of deep diving submersibles are usually welded structures, the welding distortion is inevitable, which might have a large influence on collapse strength. The authors have presented the elasto-plastic analysis using three dimensional finite element in the first report to estimate collapse pressure reduction of general instability by initial imperfection.
To investigate the infuence of initial imperfection of complex mode and that on the overall structure, however, more effective mothod is required instead of the three dimensional analysis.
In the present paper, the authors propose the elasto-plastic analysis using the quasiaxisymmetric finite element, which represents the deformation of stiffened shells by Fourier series. The analytical results compared with those obtained from the current full three-dimensional analysis show a good agreement. Futhermore, the authors investigate the influence of initial imperfection on the collapse strength of scale models, which are machined or welded, by comparing the results of the theoretical analysis and those of experimental test.
