Research, Energy Orthogonal

The energy-orthogonal character of Wilson element,Q₁ element,rotated Q₂ element,Bergan 9-parameter triangular element[6],5- parameter[23] and 8-parameter rectangular element[20] is analysed in this paper.Because of shape function space being energy-othogonal ,the stiffness matrices of these elements are block diagonal.This will make it easier to sovle the system of linear equations at last.In this paper,4-parameter element,6-parameter element, 12-parameter triangular elements and a 12-parameter rectangular energy-othogonal element which has two sets of parameters are presented.Under the conventional regular assumption their error estimates are ob-tained.Meanwhile, the superclose feature of 4-parameter triangular energy-othogonal element is proved and using the similar method with [22],the error estimate of this element on anisotropic meshes is given.The 12-parameter triangular element is high accuracy.