Some observations on the enforcement of constraint equations in the EFG method

Formulations are presented to enforce constraint equations in the element-f ree Galerkin (EFG) method by means of Lagrange multipliers and by penalty f unctions. These formulations include prescribed values for degrees of freed om as well as relations between degrees of freedom. The formulations are te sted on two benchmark problems. Due to the smooth character of the EFG shap e functions, inaccuracies such as oscillations may appear near abrupt chang es in the boundary conditions. It is argued and shown that the use of nodal integration, instead of Gauss integration, for the boundary integrals redu ces these deficiencies importantly. Copyright (C) 2000 John Wiley & Sons, L td.