Influence of Geometric Characteristics on Fatigue Behavior and Life Evaluation of Deep-water Platform Welding Structures

Fatigue damage is the main cause for the structural damage of the deep-water platform. The fatigue life test of the butt and T-welded joints of the EH36 steel commonly used at sea proves that the joint form is the main reason affecting the fatigue life. Besides, the fatigue life of the welded joints has strong fatigue dispersion. With the decrease of the stress range, the fatigue life dispersion degree increases gradually. The fatigue dispersion degree of the T-welded joint is greater than that of the butt welded joint. The coupled digital image correlation(DIC) monitoring of the fatigue behaviors of the welded joints shows that the T-shaped welded joint shows greater stress concentration and stress gradient effect, and that the shape of the weld toe and stress range are the main reasons affecting the fatigue life dispersion degree of the welded joints. In the evaluation of the hot spot fatigue life, the 0.4t-1.0t extrapolation points have more accurate and effective calculation results, but the hot spot stress has to be divided according to the recommended grid size in the fatigue design.