Stability of imperfect stiffened conical shells

A general procedure is developed for stability of stiffened conical shells. It is used for studying the sensitivity behavior with respect to the stiffener configurations. The effect of the pre-buckling nonlinearity on the bifurcation point, as well as the limit-point load level, is examined. The unique algorithm presented by the authors is an extended version of an earlier one, adapted for determination of the limit-point load level of imperfect conical shells. The eigenvalue problem is iteratively solved with respect to the nonlinear equilibrium state up to the bifurcation point or to the limit-point load level.A general symbolic code (using MAPLE) was programmed to create the differential operators based on Donnell’s type shell theory. Then the code uses the Galerkin procedure, the Newton–Raphson procedure, and a finite difference scheme for automatic development of an efficient FORTRAN code which is used for the parametric study.