An equilibrium model for plate bending

A conforming displacement model for plate bending was presented earlier. It is of intyerest to have also an equilibrium moàdel available in order to generate both upper and lower bounds to plate deflections. The theory of the triangular equilibriium model, which is presented here, takes advantage of oblique coordinates. Il allows to cover transvers loading modes. Because the numerical investigations required adaptibility of the model to a stiffness computer-program, only the elaboration of the stiffness matrix was aimed at. The element can nevertheless be recognised as the Southwell analogue of the plane stress model with quadratic displacement field. As such it can be handled efficiently by a force program. Numerical results show the monotonic convergence of deflections from above for the equilibrium model and from below for the conforming model. The convergence rate, in terms of generalized coordinates, is compâred with that of other plate bending elements.