Characterization of welded steel joints using modal shapes

The widely used component method proposed in Eurocode 3 Part 1.8 for the characterization of steel joints has limitations that arise from their accuracy and the difficulty to take into account all the interactions between the different components, especially for three-dimensional joints where the method becomes impracticable. Continuing with the methodology of characterizing steel joints using complete finite element models that are substructured to 12 degree of freedom cruciform elements, we examine in this paper the use of different sets of eigenvectors (based on different boundary conditions imposed on the cruciform element) to assess the stiffness and resistance of the joint. A study of the participation of the eigenvectors in frame analysis shows the modes that contribute to the joint response in displacements and internal forces. Whereas the eigenvectors characterize the stiffness quite well, they do not seem suitable for resistance characterization due to their strong coupling.