KOITER STABILITY THEORY IN A COMPUTER-AIDED ENGINEERING (CAE) ENVIRONMENT

The development of "DISDECO", the Delft Interactive Shell Design Code is described. The purpose of this project is to make the accumulated theoretical, numerical and practical knowledge of the last 20 years readily accessible to users interested in the analysis of buckling sensitive structures. With this open ended, hierarchical, interactive computer code the user can access from his work-station successive programs of increasing complexity. Included are modules that contain Koiter's imperfection sensitivity theory extended to anisotropic shell structures under combined loading. The nonlinear Donnell-type anisotropic shell equations in terms of the radial displacement W and the Airy stress function F are used. The circumferential dependence is eliminated by Fourier decomposition. The resulting sets of ordinary differential equations are solved numerically via the "Shooting Method". Thus the specified boundary conditions can be enforced rigorously not only in the pre-buckling but also in the buckling and post-buckling problem. Initial results indicate that in order to obtain reliable results for anisotropic shells rigorous enforcing of the edge restraint and of the boundary conditions is indeed a must. © 1990.