In this paper, a new and efficient method for welding simulation is proposed. This method, known as Smart-GFEM introduces in a GFEM framework an enrichment function which is capable of adapting the approximation space optimally. The enrichment function can be seen as a computational vademecum which depends on technological and material parameters of the process and it is completely computed off-line. In this work we present how to perform the thermal analysis of the welding and a general strategy to address the mechanical analysis.