Free vibration analysis and design aids of stiffened conoidal shells

The application of the finite element formulation for stiffened shell structures is proposed by the appropriate combinations of the eight-node doubly curved isoparametric shell element with the three-node isoparametric curved beam element. The accuracy of this formulation is first established by comparing it with the results of various numerical problems available in the existing literature. Then, the finite element formulation is employed to study the free vibration behavior of a clamped stiffened conoidal shell with respect to stiffener orientations (along x, y, and both x and y directions), stiffener types (concentric or eccentric), number of stiffeners, and stiffener depth to shell thickness ratio d(st)/t. Finally, the authors propose design aids by introducing charts, useful to the designers, with nondimensional parameters to obtain the fundamental frequency of clamped stiffened conoidal shells of different spans. widths, and other physical dimensions commonly adopted for construction specifying clearly the range of validity in the text.