Influence of Initial Geometrical Imperfections on Vibrations of Axially Compressed Stiffened Cylindrical Shells

摘要

The vibrations of stiffened cylindrical shells having axisymmetric or asymmetric initial geometrical imperfections and axial preload are studied. The analysis is based on a solution of the Karman-Donnel nonlinear shell equations, an 'exact' solution of the compatibility equation, and a first order approximation by the Galerkin method of the equilibrium equation. The stiffeners are closely spaced and 'smeared' stiffener theory is employed. An extensive parametric study is carried out on shells similar to those used in vibration and buckling tests. The results show that stiffening of the shell will lower the imperfection-sensitivity of its free vibrations, but the decrease depends on the type of stiffening (stringer or rings), the mode shapes of the vibration and the imperfection, the stiffener strength and eccentricity. The imperfection-sensitivity decrease, caused by the stiffeners, is greater for vibration mode shapes with high imperfection-sensitivity than for other vibration mode shapes.