Study of Rack and Chord Assembly Formability for Jack-Up Platforms

Abstract

Fatigue cracking is probably the major cause of service failure of jack-up rigs, and the use of high-strength steels, which permits higher static stress limits, can exacerbate this problem. Hydrogen-induced stress corrosion can also occur, either due to cathodic corrosion, particularly in the presence of H2S in foul sea-water. For this reason forming and weld hardness limits need to be maintained. Formability problems in jack-up rigs arise principally in leg construction where particularly high-strength steels are used for chords and racks. Attainment of mechanical properties is not usually difficult, although procedural trials are advisable. Roll forming process is one of the most widely used processes in the world for forming metals. It can manufacture goods of the uniform cross section throughout the continuous processing. However, process analysis is very difficult because of the inherent complexity. Therefore, it is time-consuming and much money is needed for manufacturing goods. In order to overcome this difficulty, computational method based on the rigid-plastic finite element method is developed for the analysis of roll forming process.