Abstract: The no-smoothness resulting from changes of contact state is the main reason of nonlinearity in contact analysis; but this no-smoothness can be approximated by constraint function; and then Newton method or Newton-like methods can be used to acquire its approximate solution. The conventional Goodman element is the most frequently used model in the numerical simulation of structural planes; but there are some difficulties in parameter determination and computing convergence. By constraint function method, the conventional problems in Goodman element can be solved easily. The detailed format of its finite element method is given; and then a simple method dealing with rigid displacement is also given. Finally, combined beams and dam foundation #3 of the Three Georges Project are computed as examples.

Key words: contact problem, constraint function method, finite element method, Goodman element, rigid displacement