Analysis of mechanical response for twisted mooring chains

The twist of chain for a mooring system of offshore oil platforms is often generated which could cause high stress level in the chain and affect safety of the mooring system. In this paper, a geometrical frictionless theory for predicting the torsional response of chain is introduced. The stress distribution of chain link, change of contact region between adjacent links, relationship between torque and twist angle, and relationship between gap per link and twist angle are analyzed for both stud-less and stud-link chains by using nonlinear finite element method. Finally, based on a large number of numerical simulation data which can consider the friction effect, the upper bound regression formulae are derived for predicting the torque of chains. The numerical results have significance for a better understanding of the torsional response and safety assessment of a twisted chain. ©, 2014, China Ship Scientific Research Center. All right reserved.