## ABSTRACT

For the CST, the linear displacement model, equations (4.1) can be written as

Or, when evaluated at particular nodes it produces equations (4.4) {U'} = u, x1 Y1 0 0 0 ()(1 =[A]{()(}

u2 Xz Yz 0 0 0 C1.z u3 1 x3 Y3 0 0 0 (13 vl 0 0 0 1 x1 Y1 /31 Vz 0 0 0 Xz Yz flz v3 0 0 0 x3 Y3 /33

(Note {U} has the terms reordered in {U'} to produce [A] which is inverted more easily.) However, the solution requires the elimination of a 1 etc., i.e. matrix [A] must be inverted:

{a} = [A] - 1 {V'} giving

where (x1,y 1) are coordinates of node 1 etc., and - (X1Y3-Y1X3)

and similarly for v.