FREE-VIBRATION ANALYSIS OF ORTHOTROPIC PLATES RESTING ON PASTERNAK FOUNDATION BY MIXED FINITE-ELEMENT FORMULATION

In mixed finite element formulation three different methods: (1) Helli nger-Reissner principle (HR); (2) Hu-Washizu principle (HW); (3) Gatea ux Differential Method (GDM), are widely used. In this study using the GDM, a functional and a plate element capable of modeling the Kirchho ff type orthotropic plate resting on Winkler/Pasternak (isotropic/orth otropic) elastic foundation are given and numerical results of a free vibration analysis is performed. The GDM is successfully applied to va rious structural problems such as space bars, plates, shells by Omurta g and Akoz. The PLTEOR4 element has four nodes with 4 x 4 DOF. Natural angular frequency results of the orthotropic plate are justified by t he analytical expressions present in the literature and some new probl ems for orthotropic plate on elastic foundation (Winkler and Pasternak type foundation) are solved. Pasternak foundation, as a special case, converges to Winkler type foundation if shear layer is neglected. Res ults are quite satisfactory. (C) 1998 Elsevier Science Ltd. All rights reserved.