Free Oscillations of a Composite Structurally Orthotropic Cylindrical Shell Stiffened by Discretely Positioned Ring Ribs

A method for calculating the natural oscillations of a cylindrical shell of an orthotropic material is proposed. The shell is stiffened by a set of sufficiently densely positioned transverse-longitudinal ribs, the arrangement of which allows "smearing" and contains sparsely positioned discrete stiffening rings. The shell may have a closed or open cross section; it is considered to be loaded by external pressure and axial forces. The problem is reduced to a set of homogeneous algebraic equations the number of which is equal to twice the number of discrete ribs; the equation was obtained in explicit form. The comparison of the calculated and experimental data is provided.