| It's very important about ship security to analyse the ultimate strength of hull girder. Structure invalidation is almost non-linear-geometry non-linear and material non-linear, the panels of hull girder may collapse or buckle before it reaches the yield stress, which brings the difficulty to analyse the ultimate strength of hull girder. So It's very important to gained the curve of the stress-strain, according to IACS Common Structural Rules for Oil Tankers, this thesis develops a program for oil tankers by an incremental-iterative approach.Firstly, the incremental-iterative approach needs to separate the girder hull into many elements-pulled one and pushed one. Secondly, when the ship is in hogging or sagging, you should assume one curvature value so you can get the moment value of every element at this curvature. And then you may add up all the moment of every element. Thirdly, you must judge whether the moment is the ultimate moment. If not, increase the curvature, and redo the above steps until get the ultimate strength. These procedures can be realized by one circulation. In every step, the curve of stress-strain is modified, so the result is more precise.According to the above, in this thesis, the author checks results from her program which has been compiled by FORTRAN 90 on three steel boxlike models and four ships. The author's program can resolve the following problems: ultimate strength of hull girder, the panel's curve of stress-strain. The author checks with some famous experts' results from International Ship & Offshore Structures Congress. The result is approving. And the author calculates the ultimate bending moment of two boxlike models and two oil tankers by the single step method, and compares with the result of the author's program. The two results have a little difference. The author analysis the influence of yielding stress of the material and thickness of attached plating and modulus of elasticity to the ultimate strength of the model and hull girder.
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