The Calculation And Analysis On Longitudinal Ultimate Strength Of Ship Hull Girder For Bulk Carrier

The longitudinal ultimate strength of ship hull girder represents the true strength reserve of ship girder. So it is an important index to express the safety of ship structure. The Common Structural Rules (CSR) required that the hull girder ultimate strength should be calculated if the ship length is equal or greater than 150m. At present, there are four main calculation methods: direct calculation method, progressive collapse analysis method, idealized structural unit method and nonlinear finite element method.Until now, the study of ultimate strength is still dominated by deterministic safety factor method. In fact, a variety of factors in structural analysis are uncertain, so it is very difficult to reflect the actual safety level of a ship. However, the reliability method is expressed by probability form, and it concedes clear that the possible of structural failure is existent. In order to assess objectively the load bearing capacity of ship structure and safety margin, the reliability analysis for ultimate strength has became more and more important.In addition to reliability, Economy of ship is also very important. Therefore, it is need to know the influences weight of various elements on ultimate strength.Aim at this problem mentioned above, the thesis takes a bulk carrier as an example to complete the calculation and analysis of longitudinal ultimate strength of ship hull girder. The following subjects are studied in the thesis:(1) Longitudinal ultimate strength of ship hull girder is calculated by single step method belonging to direct calculation methods.(2) Based on the research about failure mode of constitutional units, according to progressive collapse analysis method, Longitudinal ultimate strength of ship hull girder is calculated with calculation procedure the author compiled, finally, the calculate results is analysised.(3) According to the research about characteristic probability of the ship hull girder's load and the resistance to bend, the authors derived the numerical method of reliability indexβwith the advanced first-order second-moment method(AFOSM) and worked out a computation procedure, the actual safety level of the ship is analysed. At the same time, the author proposes a simple method to solve the characteristic probability of ultimate strength, the method is simple and practical, and it is suited to engineering application. (4) The type and weight of influence factors for ultimate strength is discussed by sensitivity analysis method.