Collapse Safety Reserve Of Jacket Platform Considering Damage

The jacket offshore platform suffers not only complicated marine environmental loads such as wind, wave, current and ice, but also threatened by seismic loads which are unpredictable. In such a harsh marine environment, environmental corrosion, marine organism attachment, foundation erosion, component defect, fatigue crack growth and other unfavorable factors also bring a threat on the service safety and durability of structure. At present, there are some problems in the current investigation of jacket offshore platform. The safety analysis of jacket offshore platform is concentrated on the design structure, which is seldom considered the influence of the initial defects and damage. The quantitative evaluation of component failure or corrosion damage is rarely performed. For members and connections in offshore platform, the deterioration characteristics of strength and stiffness could not be efficiently simulated by traditional beam element model subjected to strong earthquakes. The typical jacket offshore platform has been selected and the collapse safety reserve of jacket platform considering damage has been performed. Mainly researches are as follows:On the basis of reviewed a large number of domestic and foreign articles, the main research status of the structural collapse analysis of jacket platform are reviewed. The research status and analysis methods of the component importance are summarized. The research progress of structural deterioration and the hysteretic model are introduced.The damage of local components may lead to progressive collapse of the whole jacket platform structure. Using the conventional encountered ice condition as the environmental factor, The nonlinear Pushover analysis was carried out on the defect structure after removing each member. Deformation energy, strength reserve ratio and modal are considered as the level of component importance. The importance of each member is evaluated by the obtained component importance index; Weak paths caused by different first-to-fail members were analyzed to determine the weakest path in the structure and the location of the starting member in said path. Then, the weak path of the structure was regulated by adjusting the cross sections of a few members on the basis of the component importance index under the condition of constant total steel mass.The corrosion environment of offshore platform is partitioned, and the corrosion model is established according to the corrosion law of different corrosion zones. The RSR was got by the Pushover analysis of whole life jacket platform structure. The Collapse Margin Ratio was got by the incremental dynamic analysis of whole life jacket platform structure. Descending rule of the collapse strength reserve ratio of the jacket platform structure is obtained, and the effect of corrosion on the safety reserve of the collapse of the structure is analyzed.The proposed corrosion damage index based on strength reserve and the multi-mode-based damage index model has been used to evaluate the corrosion damage of jacket platform structure. The multi-mode-based damage index model has been used to evaluate the seismic damage of jacket platform, and the analysis of current problems has been point out.The skeleton curves and hysteretic rules of I-K model have been summarized. The degradation of post-capping strength, basic strength deterioration, accelerate stiffness and unloading stiffness have been analyzed. The plastic hinge finite element model of jacket platform which is used the improved I-K degradation model has been built by the OpenSees software. The dynamic performance analysis of jacket platform considering deterioration is realized.