“…Besides these techniques, there exist methodologies where the unilateral constraints are maintained in the formulation of the problem. These techniques lead to quadratic programming or linear complementarity problems which can be solved by a variety of mathematical methods, for example, Lemke's or Dantig's algorithms (Lemke, 1968;Ascione and Grimaldi, 1984;Joo and Kwak, 1986;Barbosa, 1986;Silveira, 1995;Koo and Kwak, 1996;Hexiang et al, 1999;Silva et al, 2001;Silveira and Concalves, 2001;Wriggers, 2002;Pereira, 2003;Hollanda and Concalves, 2003). Mathematical programming resembles the force method of structural analysis, thus the local contact loads are set as unknowns and the solution is obtained by minimizing a given function (Chand et al, 1976;Fisher and Melosh, 1987).…”