A free vibration analysis is developed for a ring-and-stringer-stiffened circular cylindrical shell with various types of end conditions and with the stiffeners treated as discrete elements. The number and spacing of stiffeners are arbitrary, so that there is no limitation due to averaging stiffener effects over the shell surface. The analysis shows that stringers considered as discrete elements couple circumferential modes of different wave numbers and also couple symmetric and antisymmetric circumferential modes. Moreover, the natural frequencies associated with the symmetric and antisymmetric modes may have different values, indicating the existence of "double resonances." Numerical results show that even stringers that are comparatively weak in bending may have a significant effect on both the modes of vibration and differences between the symmetric and antisymmetric frequencies. Nomenclature A = stiffener cross-sectional area D = isotropic plate flexural stiffness, Eh*/12(l -D x ,D y -orthotropic plate flexural stiffnesses due to rings and stringers, respectively E = Young's modulus (GJ) = stiffener torsional stiffness K,L = total number of rings, stringers NX™ = stringer stress resultants; see Fig. 2 N x (C \N xy^ = shell stress resultants; see Fig. 2 R = shell radius X m = axial mode functions a = length of cylindrical shell £xx, Zyy, &xy = strains in the x-y plane / = frequency drk'j dsi = radius of gyration of the kth ring, Ith stringer cross section about the x } y axis h = shell thickness i> J> k, l } m, n, P, Q = integers m*, n* -maximum number of terms used in the axial, circumferential displacement series p r k', Psi = polar radius of gyration of the kth ring, Ith stringer cross section about the y, x axis u, v, w = shell middle surface displacements in the x,y } z directions Presented as Paper 67-71 at the AIAA 5th Aerospace Sciences

No abstract

No abstract

No abstract