Abstract In this paper, the procedure is established to analyze the ultimate  strength of damaged hull girder caused by  the collision or grounding with  consideration of  the asymmetry of  cross section  and instantaneous shift of neutral axis of cross section. The advanced progressive collapse analysis method is applied. The relationship of the ship section element stress—strain is calculated with consideration of the interaction between the stiffer and attached plate, the influence of  distorts  of stiffener, torsional-bending buckling and local  plating  buckling. The effect of the damage location  on  the residual strength of hull girder is investigated in  both  sagging and  hogging conditions. Through the study of  varying parameter of  damage extent, the changing rate of the residual strength index of damaged hull girder is studied and compared in different seagoing condition. An example, 34,000 ton  bulk carrier  with large deck opening, is analyzed for demonstration.   Keywords Ultimate Strength; Residual  Strength Index; Damaged Ship; Collision; Grounding Introduction Hull girder strength is the most fundamental strength of ship structure. Generally, ships  have  been designed to resist all loads expected to arise in their seagoing environment.58678
The objective in structural design has been to maintain a ship structural integrity for normal operating conditions. A combination of the most severe loads is  usually selected as the normal  design load. However, the catastrophes which cannot be avoided will induce the loss of the ships, cargo and life at sea, even the oil pollution which  require expensive clean-up and cause long-term environmental damage. The total losses of all ships  during the years 1995-1998 are 674 in number and  3.26 million in gross tonnage (GT), according to LR of Shipping’s World Causalty Statistics. Total losses in  GT  during the years  1995-1998 are present in following figure. Grounding (wrecked/stranded) accounts  for total losses amounting to 17% in number and 24% in GT. Collision accounts for total losses amounting to 11% in GT. A ship may  collapse after an accident  (such as the collision and grounding) because  of inadequate longitudinal strength  or suffering from the severe seagoing environment. The impact that damage has on the overall residual strength of the structure is a function of its extent,  mode of failure and relative shipboard location.     Fig. 1: Total losses of ship in GT during the years 1995–1998. Until now, many research works focused on the ultimate strength of intact ship hull are conducted in both theory and experiment. The methods applied by the researchers can be classified into: 1. Simple methods: Initial yielding; Elastic analysis; and Assumed stress distribution, 
2. Advanced methods:         Progress collapse analysis with idealized relationship of stress-strain; Progress collapse analysis  with computed relationship of stress-strain; ISM; and Non-linear FEM.  In  the ISSC report  (2000),  the methods are assessed from the viewpoint  of applicability. Each method was quantitatively graded with  respect to 15 capabilities by scoring  1-5. It was also  done qualitatively by  showing  the consequence of  omitting capabilities by low, medium and high. Of these methods, the method based on  Initial Yielding is an empirical one. Methods based on Elastic Analysis and Assumed Stress Distribution are direct methods,  whereas the remaining methods  have the capability to trace  out the  full sequence of progressive collapse behavior  of the  hull  girder. It is seen that the most effective among all methods is Progressive  Collapse with Calculated  ε σ − Curves, that involves the use of numerical methods to determine the stress-strain cures of inpidual plate and stiffened plate elements, which are then integrated  following the assumptions of simple beam theory in order to trace out the progressive collapse curve (ISSC, 2000). In recent years, the focus of ship hull ultimate strength turns to the  damaged ship. In the Report  of Ship Structure Committee (1995),  the  following tasks are performed: 1.  collecting and evaluating the damage of marine structure;  2. summarizing the state of the art technology and methods  available in  marine and non-marine industry for quantifying residual strength; 3. recommending future work to investigate current engineering  procedures in the areas  of crack growth, permanent deformation  and global ultimate  strength  to assess  residual strength  of damaged marine. Zhang (1996)  proposed a  semi-analytical method of assessing the residual longitudinal strength of damaged ship  hull. Paik et al (1998) analyzed the residual strength  of  bulk carrier in grounding and  residual strength of ships after  collision and grounding. In the paper, the location and  amount of  collision and grounding damage were  prescribed. The possibility  of hull collapse  was explored by a comparison  of the applied extreme bending moment and the ultimate hull strength  which were  estimated using design oriented methods and formulas. Two  types of  residual strength index,  namely the section  modulus based residual strength index and the ultimate bending strength based residual strength index,  were defined.  Wang  (2002a) first reviewed the  state-of-the-art research on  collision and  grounding.  It  focused on the three issues that a standard for design against accidents needs to address: definition of accident scenarios, evaluation approaches, and the acceptance criteria. Laterly,  Wang(2002b) investigated the longitudinal  strength of  damaged  ship hulls  for a  broad spectrum of collision and  grounding accidents. Both the hull girder section modulus and hull girder ultimate based  on the appropriate approach are calculated. 船体梁极限强度英文文献和中文翻译:http://www.751com.cn/fanyi/lunwen_63528.html