A series of fatigue tests has been carried out for steel T-shap ed tubular joint specimens with different weld toe radius by Yagi et al.. Through the tests, interesting fracture patterns were found at the chord/brace intersection. The patterns were characterized by the toe radii. In the experimental observation, the surface crack was curved along the crack width and depth. In addition, a twisted fracture surface can be found in a joint with relatively large toe radius. To investigate the fracture behaviors, stress analysis and crack propagation simulation are carried out employing advanced numerical metho ds, i.e., finite element metho d (FEM) and eXtended FEM (X-FEM). Through the experimental and numerical studies, mechanisms of the fatigue fracture phenomena are carefully examined. It is found that change of the deformation around the crack before/after the wall penetration affects the twisted surface generation.
