Application of efficient TEP FE computation on accurate fabrication of cylindrical leg structure of jack-up rig

Cylindrical leg structure is an essential component of jack-up rig, and its fabrication accuracy will significantly influence the operation performance and service lift. Due to the welding distortion generated during rack and cylinder joining and its effect on dimensional profile of cylindrical leg structure, the experiment to fabricate the cylindrical leg structure and dimensional measurement were conducted in advance, and highly efficient Thermal Elastic Plastic (TEP) FE computation with Iterative Substructure Method (ISM) and OpenMP parallel computation was proposed and employed for welding distortion prediction. Simplified cylinder FE model was considered to clarify the mechanism of dimensional variation in advance, and efficiency of proposed TEP FE computation was also demonstrated. Quarter FE model of rack and cylinder welded structure was then employed due to its symmetrical feature while computed results have a good agreement comparing to the measurement. Meanwhile, in order to improve the fabrication accuracy, bead-on-plate welding on inner surface of cylindrical leg structure was numerically examined, while inverse deformation can be generated and has significant influence to mitigate welding distortion during rack and cylinder joining. •Effective TEP FE computation with ISM and parallel computation was proposed and employed for welding distortion prediction.•Generation mechanism of cross sectional shape variation due to welding was clarified based on computed results.•Good agreement between measurement and computed results was obtained, and computational efficiency was also demonstrated.•Welding distortion mitigation with bead-on-plate welding on inner surface was numerically considered and practiced.