Combined stability of geometrically imperfect conical shells

The paper examines the influence of axisymmetric, bulge-type shape imperfections in conical shells on buckling strength. Mild steel cones are subjected to axial load, lateral pressure, and any combination of both. Imperfection sensitivity of buckling load along the entire interactive plot for (i) inward shape deviations, (ii) outward shape deviations and (iii) both inward and outward shape imperfections is examined numerically. For all three cases the worst possible scenario is sought through the application of structural optimization. The latter employs Tabu search algorithm coupled with the FE re-analysis tool.It is shown that both inward and outward imperfections can significantly reduce the load carrying capacity. But the largest shrinkage of the interactive diagram is obtained for the case of co-existing inward and outward initial shape imperfections.

► Inward dimple-type imperfection does not represent the worst imperfection profile.
► Outward dimple-type imperfection can be more dangerous than the inward one.
► Buckling strength along the combined stability path is assessed.
► Tabu search identifies the worst inward, outward or combined imperfection.