Stability Assessment of Anchor Handling Vessel during Operation Considering Wind Loads and Wave Induced Roll Motions

摘要

The objective of this paper is to apply IMO “severe wind and rollingrncriterion (weather criterion)” for anchor handling vessels duringrnoperation. So far, this criterion is used for merchant ships greater than arncertain size and of conventional hull forms but it is not mandatory forrnspecial purpose ships like anchor handling vessels. It is consideredrninappropriate to be used in its present form due to the large initial heelrninvolved in anchor handling vessel and vessel not subjected to severernwind and roll. A slightly modified weather criterion is proposed in thisrnpaper. A quasi dynamic criterion is used for studying wind and waverneffects on vessel stability. The vessel stability depends primarily on thernmagnitude of mooring load, angle between vertical axis and mooringrnload, angle of attack, and weather conditions. The analysis is carriedrnout for loading conditions while the vessel is in operation. The quasirnstatic approach is considered for incorporating the influence of mooringrnparameters in the loading condition itself. Due to the overturningrnmoment coming from the mooring load, vessel changes to new staticrnequilibrium position. In this state the vessel is subjected to an initialrnheel angle, at the same time the vessel range of stability is reduced. Thernvessel loses its range of stability due to the overturning moment comingrnfrom the mooring load. Therefore, the area under the righting momentrncurve is drastically reduced. The reduction of dynamic transversernstability limits the allowable roll angle influenced by the waves for safernoperations. Hence, it is essential to study the influence of mooringrnparameters, and wind speed on the vessel’s dynamic stability torndetermine the allowable sea state. Alternatively, for a given sea staternand wind speed the limitation of mooring load can be determined. Thernmodified method can be useful during the planning of operatingrnguidelines regarding the stability of the anchor handling vessel.