| The offshore platform structures, very complex and expensive, are suffered from natural random loads, and they are also damaged by manufacture and collided with the vessel. Therefore, scientific analysis of the damage affect of local cracks on an offshore platform and taking effective measures timely can help slow the damage process in order to give longer life of the structure.On the basis of design information, this paper creates model by using pipe element, calculates stress situation in three cases, a method of finite element analysis of offshore platform structures is proposed through the local solid modeling and using method of coupling nodes to deal with connection of solid element and pipe element.It also verifies that the method is feasible through comparison of the results of position one local solid model in three cases.According to design specifications, the damage affect of local cracks on an offshore platform in BOHAI China, research shows that when the length of circumference of the crack is small, the maximum stress happens on the platform. The maximum stress happens on the place around the damage under the length of circumference of the crack reaches a certain value. With the increasing of length of circumference of the crack, the stress around the damage continues to grow. While the length of circumference of the crack of position one reaches 172°in case 3, position two reaches 149°in case 3, position three reaches 144°in case 2, the maximum stress around the crack reaches the material Yield Strength. When the length of Circumferential of the crack is more than the value above, the maximum stress around the crack is larger than the material Yield Strength, and the platform will be in the damage status going with the length of cracks on expanding quickly. The research provides an accurate and useful method for analysis and evaluation the influence of cracks on the whole platform structure.
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