Читать книгу Finite Element Analysis - Barna Szabó - Страница 32

Each element has internal basis functions. Those elements of the coefficient matrix which are associated with the internal basis functions can be eliminated at the element level. This process is called condensation.

Let us partition the coefficient matrix and right hand side vector of a finite element with such that

where the and . The coefficient matrix is symmetric therefore . Using

(1.77)

we get

(1.78)

The condensed stiffness matrices and load vectors are assembled and the Dirichlet boundary conditions are enforced as described in the following section. Upon solving the assembled system of equations the coefficients of the internal basis functions are computed from eq. (1.77) for each element.