This paper is devoted to the experimental and numerical assessment of residual stresses created by welding in the region surrounding the weld toe of tubular K-shaped joints (i.e. region most sensitive to fatigue cracking). Neutron-diffraction measurements were carried out on K-joints cut from large-scale truss beams previously subjected to high cycle fatigue. Tri-axial residual stresses in the transverse, longitudinal and radial direction were obtained from the weld toe as a function of the depth in the thickness of the tube wall. In addition, thermomechanical analyses were performed in three-dimensional using ABAQUS and MORFEO finite element codes. Experimental and numerical results show that, at and near the weld-toe surface, the highest residual stresses are critically oriented perpendicularly to the weld direction, and combined with the highest externally applied stresses. Based on a systematic study on geometric parameters, analytical residual stress distribution equations with depth are proposed.