Cao Yuguang

Parametric Study of Stress Concentration Factors (SCFs) on Tubular X-Joints Used in Offshore Platform Structures

ABSTRACT 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.

Static analysis of an umbilical under axial and bending loadings by FEM

Umbilical can implement the integrated functions of providing power, hydraulic channel for deep-sea underwater equipment, transmitting the chemicals required for the development of oil and gas field, transmitting the control signals from the mother ship as well as data from the underwater equipment sensors. With the development of offshore engineering goes to deep-water day by day, the design, manufacturing, and other technologies of the umbilical need to be solved urgently. This paper carried out static analysis of an umbilical under axial and bending loadings by FEM, obtained the umbilical tensile stiffness and bending stiffness, and compared the results of FEM with other theoretical studies. The research can provide technical support for the design and manufacturing of the umbilical.

Structural design of an offshore hydraulic energy-storing workover rig

After more than ten years’ development, the functions of workover rigs in China can generally satisfy the demands of offshore oilfield production. For conventional workover rigs, large working space and guide rails are necessary, and they bring trouble to the workover operations. The high cost of manufacture, transportation, installation and running such general workover rigs is also an inevitable problem. Because of the advantages of the hydraulic energy-storing workover rigs, such as energy saving, environmental protection, small occupation and convenient installation, they have been widely used in onshore oilfields. In this paper, the preliminary structural design of a newly developed simple offshore workover rig will be introduced and the feasibility of applying this type of rig will be discussed.