Hybrid-stress six-node prismatic elements

This paper presents three novel hybrid-stress six-node prismatic elements. Starting from the element displacement interpolation, the equilibrating non-constant stress modes for the first element are identified and orthogonalized with respect to the constant stress modes for higher computational efficiency. For the second element, the non-constant stress modes are non-equilibrating and chosen for the sake of stabilizing the reduced-integrated element. The first two elements are intended for three-dimensional continuum analysis with both passing the patch test for three-dimensional continuum elements. The third element is primarily intended for plate/shell analysis. Shear locking is alleviated by a new assumed strain scheme which preserves the element accuracy with respect to the twisting load. Furthermore, the Poisson’s locking along the in-plane and out-of-plane directions is overcome by using the hybrid-stress modes of the first element. The third element passes the patch test for plate/shell elements. Unless the element assumes the right prismatic geometry, it fails the patch test for threedimensional continuum elements. It will be seen that all the proposed elements are markedly more accurate than the conventional fully integrated element