Steel structures are mainly prone to two types of degradation: corrosion and fatigue particularly in the case of welded structures. The presented work aims at investigating two treatment methods to increase the fatigue life expectancy of welded steel joints in civil engineering structures. It includes both numerical and experimental investigations and is interested in the use of grinding and shot peening. As far as experimental investigations are concerned, for both treatment methods and for untreated samples, the stress concentration coefficients are determined, surface residual stresses are measured using X-ray diffraction and fatigue tests are conducted. The results allow explaining for both methods the observed improvements in fatigue behaviour. As far as numerical investigations are concerned, the presented work concerns the use of a finite element model to simulate welding process. This allows the determination of residual stresses due to welding operation and their comparison with the former experimental measures. Results are satisfactory enough, and, though some improvements regarding the initial stress state and the modelling are still under progress, it should be used in a following study to model treatment operations to get a better understanding of their potentiality and the parameters that affect their efficiency.
