A design chart for the plastic collapse of corrugated cylinders under external pressure

The paper presents a theoretical and an experimental investigation into the plastic collapse of circular steel corrugated cylinders under external hyd rostatic pressure. The experimental investigation gives la detailed study o f 9 steel corrugated cylinders which were tested to destruction. Six of the se cylinders failed by plastic non-symmetric bifurcation buckling and three failed by plastic axisymmetric deformation. The results of these tests wer e used, together with the results obtained from previous tests, to present a design chart for the plastic collapse of these vessels. The design chart was obtained by a semi-empirical approach, where the thinness ratios of the vessels were plotted against their plastic knockdown factors. The process of using the design chart is to calculate the theoretical elastic instabili ty pressure for a perfect vessel by the finite element method and also to c alculate the thinness ratio for this vessel. Using the appropriate value of the thinness ratio, the plastic knockdown factors are obtained from the de sign chart. To obtain the actual collapse pressure of the vessel, the theor etical elastic instability pressure for a perfect vessel is divided by the plastic knockdown factor. This work is of importance in ocean engineering. A large safety factor must also be introduced. (C) 2000 Elsevier Science Lt d. All rights reserved.