Single Leg Catenary Mooring and Anchors

Abstract

Single leg catenary systems with short scope (ratio of total chain length to water depth) are often required to be designed to resist the dynamic forces due to the movement of the moored vessel. In order to prevent impact loads on the system, it is necessary that the total kinetic energy imparted to the system by the moored vessel is absorbed by the potential energy inherent in the SLC system. The kinetic energy is a function of the velocity or drift of the moored vessel, a known quantity; while the potential energy is a function of the weight of the riser chain, an unknown quantity that must be determined. The critical loading results from a reversal of wind and current forces which cause the moored vessel to move across the mooring area and pass directly over the anchor point. A method is presented which utilizes an energy approach to determine the weight of the riser chain required to prevent impact loads on the system at the maximum excursion at maximum load.