Approximate Method for Calculating Dynamic Tension of Mooring Chain

This paper deals with the approximate method for calculating the dynamic tension of the mooring chain which is anchored in slack condition on the sea bed and is forced to oscillate vertically and horizontally at its upper end. An extensive series of experiments has been conducted to clarify the mechanism of generating the dynamic tension and the snapping of a mooring line. Using the results of experiments, the cable's shape during oscillation is approximated as a catenary line. Moreover, the oscillation of a mooring line is idealized as a single-degree-of-freedom motion of one lumped mass. The dynamical equation of the motion of the mass are solved over a broad range of forcing amplitude and periods of practical use, and their threshold values for the snap are obtained analytically. The calculated results are in good agreement with those of the experiments.