Shielded Metal Arc Welding (SMAW) remains one of the most widely used joining processes across industrial sectors, particularly in the nuclear industry, where it is well suited to constrained environments and repair operations. In many practical situations, welders deliberately employ a weaving motion to increase bead width, adjust lateral heat input, or control penetration. These oscillations generate a specific thermal distribution that differs significantly from that produced by straight‑line welding passes. In this context, numerical simulation provides a powerful tool for analysing the influence of weaving and operational parameters on the thermomechanical behaviour of the process, especially regarding residual stresses and strain hardening. The objective of this study is to establish a modelling methodology capable of accurately capturing the effect of weaving in the SMAW process. First, this work introduces the development of a three‑dimensional thermomechanical model dedicated to SMAW simulation using the finite element code code_aster [1], explicitly incorporating the oscillatory motion of the electrode. The thermal model relies on a moving heat source with a Gaussian distribution, adapted to reproduce the characteristic morphology of a molten pool subjected to weaving oscillations. The heat source path is defined from experimental instrumentation, including video analysis of a welding test performed on a pipe configuration. In parallel, a methodological study is carried out to assess the ability of two‑dimensional models to approximate the effect of weaving, allowing for more computationally efficient simulations suitable for parameter sensitivity analyses [2]. The proposed numerical approach thus provides a robust tool for detailed investigation of weaving strategies and for optimising welding parameters within a predictive framework aimed at improving joint quality. REFERENCES [1] Electricité de France. Finite element code_aster , analysis of structures and thermomechanics for studies and research, 1989–2023. [2] V. Robin, S. Hendili, J. Delmas, S. Hilal, D. Iampietro , M. Abbas and S. Jutteau : Modelling of residual stresses in multi-pass pipe circumferential butt welds made of austenitic stainless steel to provide indicators for SCC risk classification, PVP2023-107448, Proceedings of the ASME 2023 Pressure Vessels and Piping Conference.