Abstract:The jacking pinions and rack chocks of the fixation system of a jack-up sustain tremendous load in the elevated condition, especially when there exists a remarkable non-uniformity of the load distribution. Failures of these structural components may lead to disastrous consequence of the jack-up. Despite the importance of these components, it is difficult to give an accurate prediction of the load distribution on these components in engineering application due to the complex nonlinear interaction mechanism, which is influenced by the relative stiffness of the components, leg-guide clearance and backlash. Previous studies mainly focus on the global performance of the jack-up and pay little attention to the load distribution on the pinions and chocks. The strength of the jacking system is often guaranteed by the manufacturer for an estimate load level, which brings in uncertainty to the safety of the jack-up. The characteristics of the hull-leg interaction are discussed in this paper, and a simplified method using gap elements is proposed. The nonlinear structural analyses are carried out for a specific jack-up using the proposed method and the three-dimensional finite element method (FEM) with contact algorithm. The proposed method is proved accurate and effective for the engineering application. The characteristics of the load distribution of the specific jack-up are discussed, and the conclusions are presented.

Key words:jacking pinions, rack chocks, load distribution, hull-leg interaction, nonlinear structural analysis

摘要：The jacking pinions and rack chocks of the fixation system of a jack-up sustain tremendous load in the elevated condition, especially when there exists a remarkable non-uniformity of the load distribution. Failures of these structural components may lead to disastrous consequence of the jack-up. Despite the importance of these components, it is difficult to give an accurate prediction of the load distribution on these components in engineering application due to the complex nonlinear interaction mechanism, which is influenced by the relative stiffness of the components, leg-guide clearance and backlash. Previous studies mainly focus on the global performance of the jack-up and pay little attention to the load distribution on the pinions and chocks. The strength of the jacking system is often guaranteed by the manufacturer for an estimate load level, which brings in uncertainty to the safety of the jack-up. The characteristics of the hull-leg interaction are discussed in this paper, and a simplified method using gap elements is proposed. The nonlinear structural analyses are carried out for a specific jack-up using the proposed method and the three-dimensional finite element method (FEM) with contact algorithm. The proposed method is proved accurate and effective for the engineering application. The characteristics of the load distribution of the specific jack-up are discussed, and the conclusions are presented.

关键词:jacking pinions, rack chocks, load distribution, hull-leg interaction, nonlinear structural analysis