Study On The Green Water Load Of Low Freeboard Ships And The Influence On Structural Strength Of Deck Equipment

In order to meet the requirement of work and task,the hull form of low freeboard is adopted in ship building,which is very prone to significant green water on deck while sailing on sea,and leading to damage of structures on deck.Thus,the structural strength of the low freeboard ships under green water on deck is the premise and foundation of rationally designing the ships.However,current studies of green water on deck mostly concentrate on bow deck in head sea state,and the study on green water on broadside is less.To solve the green water problem on broadside deck of low freeboard ships,following contents are studied based on the wave load calculation,model testing,dam break theory and oblique impact theory:(1)The motion of the low freeboard ship in regular waves and irregular waves are calculated via three-dimensional linear frequency domain method and nonlinear time-domain analysis method.Then,based on the ship response and wave motion,the relative motion between ship and wave is calculated by spectrum analysis,random wave superposition method and time-domain analysis method.And finally,the applicability and the influence of different parameters on relative motion in regular waves are analyzed.(2)Based on the model test results,verification and improvement of dam break model are achieved to calculate the motion of shipped water on deck,and a method of calculating impact load of shipped water is achieved refer to oblique impact theory and model test.(3)In accordance with the ship mission of the low freeboard ship,the calculating conditions that are applied to structure analysis are obtained.After calculating the green water height and impact load of shipped water in different calculating condition,the design impact load is determined.Then the structural analysis about the equipment and deck structure is made to verify if the structure strength is enough,and finally,structural strengthening measures are studied.The results may be significant to the structural strength analyses on the green water region of similar ships and providing building guidance.