Free vibration of eccentrically stiffened laminated plates

The free vibration characteristics of laminated plates with discrete stiffeners are analyzed by the finite element method. The analysis takes into consideration transverse shear deformation effects and rotary inertias in the plate and stiffeners. The stiffeners are modeled as laminated beams and are placed along plate nodal lines. A C degrees stiffened plate element is developed using a nine noded isoparametric plate element and a three noded isoparametric beam element. Natural frequencies and mode shapes of eccentrically-stiffened laminated plates are presented to demonstrate the efficiency of the methodology. The influences of stiffeners such as depth, number, location and ply orientation on the natural frequencies are examined.