Research On Dangerous Zone And Damage In Different Situations Of Ship-ship Collision

Collision,stranding and other dangerous accidents will happen due to inappropriate operation,machine breakdown,unfavorable environment and unavoidable factors when ships sail on the sea.Statistics show that ship collision has ranked highest among all these accidents.Until now,scholars have been focused on the collision of ship whose bow hits vertically the side amidships.They have mainly studied on collision damage,structural crashworthiness optimization and collision mechanism,but rarely on the collision of the whole ship under different situations and sections.What's more,there is no study on the risk after collision.Once collision happens,it may result in casualties of people,loss of fortune and environment pollution,etc.Thus,how to reduce as much low collision damage and loss as possible is the most important thing.If collision is unavoidable in reality,in order to lower the damage and loss,the ship operator should adjust to the proper collision area and situation(including speed and angle).In this case,it is of significance to study the dangerous zone of ship collision and damage under different situations.Based on the finite element simulation,combined with risk evaluation method and the improved BP-GA(back propagation-genetic algorithm),the thesis takes two 10,000 DWT single-hull side structural bulk carriers as the research objects,first studies the factors that influence the degree of collision damage;then defines the dangerous zone of the ship collision which guides the ship operator to avoid more serious collision;and determines the critical velocity and angle of the ship collision by establishing the comprehensive index.At the end of it,suggestions about how to reduce the structure damage of collision and collision risk in an emergency are given to the ship operator.The related researches of this thesis are as follows:(1)Establishment of finite element model of whole ship.Taking two bulk carriers whose capacities are both 10,000 DWT as objects,the finite element models of ships are established by using finite element analysis software MSC.Patran according to the ship line drawing,typical cross-section drawing and structure drawing;based on the model,parameters such as materials,contact,boundary conditions,etc are set.(2)Discussion on factors affecting ship collision damage.Based on the situation that the bow hits the side amidships,several numerical simulation conditions are designed and the factors influencing the collision damage according to the damage results are discussed.(3)Definition of the danger zone of ship collision damage.The collision zone is divided into three sections: "the bulb-bow section of the bow","the cargo hold section amidships" and "the cabin section of the stern".The degrees of danger for the collision zones are defined respectively according to infinite element simulation of different zones and evaluation of collision risk.After comparing all the results,the most dangerous collision zone is determined.(4)Research on critical situation of ship collision.Several numerical simulation conditions including different speeds and angles are designed firstly.Then,the finite element simulation of the most dangerous zone is analyzed by MSC.Dytran and the velocity range and angle range are determined when the stern structure is unbroken.In order to get more accurate values of the critical velocity and angle,based on the situation that the stern structure is unbroken,the collision energy loss is smallest and the depth of collision(deformation dimension)is smallest,its final critical velocity and angle values are determined by using the orthogonal design and BP-GA algorithm.(5)Recommendations for reducing ship damage.Based on the analysis of the collision of two 10,000 DWT bulk carriers,the suggestions are given for reducing collision damage on the discussion from the two prospects of the emergency operation and structural optimization design.