Abstract: The hot spot stress method is widely used for fatigue life analysis of tubular joints, wherein stress concentration factor is a main parameter for calculating hot spot stress. The weld profile modeling method is put forward, and then numerical modeling of tubular K-joints is established, including hollow tubular joint and filled concrete. Then, stress concentration factor is investiged. A comparision with experimental results proves that the proposed numerical modeling method is simple, reliable and accurate.The maximum stress concentration factor of K-joints with filled concrete is about 1/3 of that of hollow K-joints, so fatigue behaviour of K-joints is improved effectively with filled concrete.