Ship Rocking Research Based On Ultimate Carrying Capacity Of Structures

The ship faces many risks such as rocking in the course of transportation, and this not only causes enormous economy loss but also makes serious sea environmental pollution, among this, the rocking accidents of oil tanker is especially heavily. Therefore, improving ship crashworthiness is of great importance, considering no matter from safety, economy or protecting environment. To study ship rocking not only benefit the life safety on the sea and preventing ocean pollution, but also offer references of ship velocity, manipulation regulations, solving maritime affairs for shipping busy regionsBecause of the enormous quantity and kinetic energy of the ship, when the ship striking (hard grounding) happens, the fracture of striking area usually exceeds elastic phase rapidly, then turns into plastic moving state, meanwhile, all kinds of damage and failure, such as fracture and buckling could happen and then causes the permanent deformation or damage of hull structure. It mainly needs to care about the local crushing and tearing caused by rock cutting in the course of rocking accident. Notwithstanding, the mechanics actions of fracture closely relate to the types of rocks (cuniform, coniform and so on), the basic theories of fracture resistance caused by plastic, cracking and friction yet are homologous. Additionally, the fluid medium around the ship, ship external dynamics and ultimate carrying capacity of rectangle plate also should be considered. Further more because the hull is welded by stiffened plates, the rupture of plate and the invalidation of welding sew also play important effect in the invalidation of structure, which directly affect the invalidation mechanism and energy absorption of structure. The resistance of structure and penetration also are influenced by the serious degree of damaged hull. At present the damage is assumed as termination when it extends to the main stiffened frame away from the rock, but this assumption should be replaced by the intensity of structure which around the rock.In the course of ship rocking, the loads that need to consider can only be the touching loads of the hull touching the rock and water stirring. And most of the rocking energy is absorbed by the bottom structure for the rock rigid usually much bigger than the bottom. The damage deformation when ship rocking happens, we should mainly concentrate on the area that the rock touches the structure, and this adumbrates that the improvement of resisting collision to the hull structure should focus on the weak area which can be easily collided, the structure strengthening of bigger range is not necessarily. It includes many unconcerned factors such as the rock essence, strength, the situation of rocking ship, the location of rocking, the circumstance and so on. All the factors make the research of rocking problem become very complicated and difficult.It researches the ultimate state design, studies and collects the ultimate carrying capacity of structures. And then analyze the basic damage mode of the main bottom structures in a integrated way using ANSYS to simulate the counterpoise rocking situation. Followingly, the rockingperformance is studied and based on the simulation, gaining the damage deformation picture of every part of bottom structures, and the changing circumstance of maximum stress and strain. Following this, the essay discusses the influence of collision capability that impacted by the rocks which have different shapes, dimensions and different collision places, obtaining the general conclusion of loads and deformation of the bottom structures based on the results of non-linear finite element program.