Cao, Y.; Zhen, Y.; Liu, C.; Zhang, S., and Meng, Z., 2018. Parametric study of stress concentration factors (CSFs) on tubular X-joints used in offshore platform structures.

Accurate information on stress distributions along an intersection is required for fatigue strength assessment of tubular joints subjected to cyclic loading. An X-joint is widely used on offshore platforms because its strength is very important for the safety evaluation of platforms. On the basis of ANSYS, three-dimensional elements were used to model the structure with welding seams. According to the thermo effect of the welding process, using birth–death element technology, a numerical simulation was performed for the welding process by coupling the temperature field and stress field. Considering that an annealing treatment is generally performed for joints after welding, the annealing treatment process was also simulated in this paper and the influence of it on welding residual stress was analysed. Considering the influence of welding residual stress, 81 models of X-joints with different geometric parameters and loading conditions were generated and their effects on the distribution of hot-spot stress around welding seams and stress concentration factors are discussed. Results presented in this paper provide references for the safety analysis of X-joints and thus help the design of offshore platforms for exploration and development of coastal gas and oil.