Experimental Study On Dynamic Response Of Mooring Buoy Under Extreme Sea Condition

As the background of north of the yellow sea(Dong Ying offshore)some 30 ton crude oil transport system of single point mooring project.Using the model test method,considering the design wave height,period,pretention,water depth.Focused on the local extreme sea conditions mooring buoy motion responses and mooring force in the above factors under the influence of the change rule.In this paper,the movement response and mooring tension of a single cable failure are discussed.According to the research,the movement response is the most obvious,with the extreme sea condition(local effective wave height 6m,cycle 12s)reaching 11 m.The extreme value of the longitudinal movement is about seven times that of the transverse motion;In the actual engineering design process,the space in the direction of longitudinal direction should be guaranteed to ensure the safety of the project.When distributing the mooring force,it is necessary to ensure the maximum bearing capacity of the mooring force in the longitudinal direction,so as to provide sufficient restoring force in the longitudinal direction.The variation of the motion component with the period is affected by the natural cycle of mooring buoy.The initial tension and the floating body draft affect the natural cycle of the system and thus affect the motion response and cable tension.The other conditions can increase the depth of the buoy and improve the stability of the buoy.At the beginning of the mooring tension is 216 kN and under the condition of same buoy drafts of 18 m exercise significantly smaller than 12 m water depth,wave height in 3 ~ 6 m test range,the longitudinal motion,both difference test range 8% ~ 27%;The difference between the two is 6% ~ 25%.It is necessary to control the initial tension level of the cable to reduce the mooring tension in extreme sea condition.It is suggested that the selection of 216 kN initial tension and 18 m depth of draft can help the buoy resist extreme sea conditions.The maximum cable tension in the above conditions(effective wave height 6m,period 10s)is about 2800 kN.Under the condition of the failure of a cable,the maximum amount of motion of the buoy in the direction of transverse movement was increased by 10 times and the maximum amount of exercise in the longitudinal direction was doubled.After the cable failure,the two working mooring forces are significantly increased,and the maximum value is more than 44% higher than that of the working mooring force in the same line.After the cable failure,the cable should be strengthened as soon as possible and the cable should be replaced.