Some basic formulae for area co-ordinates in quadrilateral elements

The area co-ordinate method, which is an efficient tool in the construction of triangular elements, has been recently generalized to construct straight-sided quadrilateral elements. In this paper, the differential and integral formulae for area co-ordinates in quadrilateral elements are presented. Consequently, the numerical integration method that must be used in the formulation of the stiffness matrix in isoparametric elements can now be discarded. Copyright © 1999 John Wiley & Sons, Ltd.