Study on jacket structural design by rule scantling and structural strength evaluation for a 20K-ton jacket platform

Abstract

Reliable structural design techniques for a wide range of offshore plant structures aimed at utilizing renewable energy and marine space as well as developing marine resources such as drilling, production and collection of oil, gas and mineral resources of the seabed are required. In order to secure the structural design techniques for the fixed offshore plant structure, the jacket structure design method and strength evaluation were carried out as initial studies. In this paper, the basic geometry of the 20K-ton jacket was determined according to the classification rules and general jacket design process. The diameter of the subsea penetration pile was determined in consideration of the size of the offshore platform and the installation depth. And the inner diameter of the jacket leg was determined so that the condition of the subsea penetration piles installation was satisfied. Brace design for the entire panel was performed considering structural safety of each member such as slenderness ratio, hydrostatic collapse, column buckling. Since the jacket structure designed by the rule scantling method has to ensure stability from the external forces such as wind, wave, current and operating loads during its entire service life, the structural analysis was performed to supplement the scantling of the jacket members. The environmental and dynamic loads were replaced with equivalent loads and applied to the beam elements of the jacket structure. It was confirmed that significant stress occurred at the upper Part of the jacket by the horizontal force due to the environmental loads and the vertical force due to the topside platform gravity, and the safety of the structure was evaluated by unity check of all the members. This jacket design process that includes rule scantling and structural analysis for scantling supplement can be effective the total design cycle and increasing the reliability of the final structure. Copyright ？ 2018 by the International Society of Offshore and Polar Engineers (ISOPE)