In this paper, critical loads and natural frequencies are calculated for simply support-ed orthotropic laminated, sandwiched and stiffened rectangular cylindrical panels. Thefollowing problems are calculated and discussed: the critical loads of the shells underaxisymmetrical and asymmetrical buckling; the buckling loads and the natural frequenciesof the panels and shells under the action of membrane forces Nx and Ny, the bucklingloads of the stiffened panels with the stiffeners outside or inside and the inf...