Construction of transition finite elements for the plane triangular family

A method of constructing mixed order strain triangles from a high order strain triangle is presented for the family of plane triangular elements. The necessary transformation matrices are given for all members of the triangular family that can be formed from the quadratic strain triangle. These transformation matrices are universal numerical matrices which are independent of the size and shape of the triangles, and are readily applicable to field problems also. A FORTRAN program listing which generates stiffness matrices for these mixed order strain triangles is provided for the user.