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Free Vibration Analysis of Longitudinally Stiffened Cylindrical Shells with Non-Uniform Stiffeners Eccentricity

In this paper, free vibration analysis of simply supported cylindrical shells with longitudinal stiffeners i.e. stringer, using Ritz method and stiffeners treated as discrete elements, is presented. In strain energy formulation, adopting sanderʹs theorem, stretching and bending characteristic of shell and also stretching, bending and wrapping effects of stiffeners are considered. However the translational inertia in three directions for shell and stiffeners and also rotary inertia for stiffeners are considered. The polynomial functions are used for Ritz functions Natural frequency results for stringers with uniform spacing and constant eccentricity have been compared with referenced analytical and experimental results, and good agreements between these have been seen. With constant stiffeners mass, the effects of non-uniform eccentricity for three types of distribution, i.e. linear form, quadratic form, and third order form were considered and natural frequencies variations, specially fundamental frequency was determined.