and

where

Equation (10.73)has a vector , which contain three internal DOFs that need to be eliminated at this stage with the help of the static condensation scheme. Defining the external DOFs (four in numbers) of the element as masters and internal DOFs (three in numbers) of the element as slaves, the stiffness matrix in equation(10.73) is subdivided as

with

The second set of equation(10.83) gives

with