Combined stiffening and in-plane boundary conditions effects on the buckling of circular cylindrical stiffened-shells

The influence of in-plane boundary conditions on the critical loads of axially compressed simply supported stiffened cylindrical shells, stiffened by stringers and by combinations of rings and stringers is studied. It is observed that the axial restraint, u = 0, at the edges and the dimensions of either the stringers or the rings characterize the type of influence experienced. In shells stiffened by “medium” and “heavy” stringers the axial restraint is a predominant factor and the “weak in shear”, N_xφ = 0, B.Cs. have only a slight secondary effect. For such shells a “stiffening” effect is observed for SS2 and SS4 B.Cs. As the stringers become “weaker” the influence of the axial restraint diminishes and the isotropic or ring-stiffened like type of behavior, “sensitivity” to the vanishing of the circumferential restraint, overcomes the “stiffening” effect due to u = 0.In shells stiffened by combinations of rings and stringers the influence of the in-plane boundary conditions is governed by the relative magnitudes of the rings and stringers under consideration. Combinations of “heavy” stringers and “weak” rings behave like stringer-stiffened shells, exhibiting the “stiffening” effect due to u = 0 whereas shells stiffened by “heavy” rings and “light” stringers tend to behave like ring-stiffened shells, revealing their “sensitivity” to the “weak in shear” boundary conditions, N_xφ = 0.