The paper presents a theoretical and experimental study of the problem of flexural vibrations of orthogonally stiffened cylindrical shells. Use is made of the analogy between a stiffened shell and a shell of homogeneous uniformly thick orthotropic material. The equivalent orthotropic elastic constants for the stif¬fened material of which the actual shell is constructed are determined from a well defined and systematic set of bending, twisting, stretching, and shearing experiments on similarly stiffened flat plates. It is shown how elastic con¬stants Sij associated with bending and twisting involve one fictitious shell thickness, say hb and constants Cij associated with stretching and shearing of the so-called middle surface involve another fictitious shell thickness, say hs. In addition, a fictitious uniform thickness hm, enters the analysis in con¬nection with the inertial mass per unit area of the shell and arises in the kinetic energy function. Special attention is given to the meaning of these various fictitious thicknesses of the equivalent orthotropic shell. It is shown that they do not occur explicitly in the final form of the energy functions or equations of motion.
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