THE MIXED FINITE-ELEMENT FORMULATION FOR THE THICK PLATES ON ELASTIC FOUNDATIONS

A new functional has been constructed for Reissner plates on Winkler f oundations through a systematic procedure based on the Gateaux differe ntial. In this functional there exists eight independent variables, su ch as deflection, internal forces and boundary condition terms (BC), w hich were included in the functional in a systematic way. The closed f orm mixed elements are created for a (6 x 8) triangular element (TR48) and a (4 x 8) rectangular element (REC32). The element does not suffe r from shear locking. Various boundary conditions are analyzed and bou ndary values were included in the global system of equations by the La grange multiplier method. An interesting property of this formulation is that the numerical results converge from above and below, depending on whether odd or even numbers of elements are used in the mesh refin ement. Numerical tests on the elements were applied in representative problems. (C) 1997 Elsevier Science Ltd.