| The ultra-deepwater semi-submersible drilling platform is one of the important equipment for the development of deep-sea oil and gas resources,which can adapt to the needs of the strategic development of the national marine power strategy.In the development of ultra-deepwater semi-submersible drilling platforms,China's construction level has been at the forefront of the world,but there is still much room for development in the future.First,for the analysis of hydrodynamic performance,it can provide effective theoretical basis for the development of dynamic positioning systems.Second,the platform is subject to complex wave loads during long-term service.The study of wave loads can provide more accurate load conditions for calculating the strength of the platform structure.Third,the evaluation and analysis of the strength of the platform structure can provide effective security for the platform.Fourth,the analysis of the fatigue life of the platform structure can provide safety guarantee for the platform structure design to meet the long-term service conditions.Fifth,in the design phase of the platform structure,only the superiority of the overall structural performance is often considered,and good construction technology can not only improve the construction quality,but also improve the economic benefits of the product,which is also an important research direction to break the construction bottleneck in the future.This article takes an ultra-deepwater semi-submersible drilling platform as the research object,and analyzes the platform wave load,structural strength,fatigue life of key nodes,and typical structural welding processes.The main research contents and conclusions are as follows:1)This article uses Geni E software to build a model of an ultra-deepwater semi-submersible drilling platform,and analyzes its motion response and profile load transfer function.The results show that the target platform has a sensitive period of 5s-25 s for the movement response of the platform structure at a depth of 4000 m,and the motion response value is large when the wave encounters three kinds of waves,namely,down,horizontal and tail.The motion response transfer function is larger in the section load in the period of 7s-10 s.2)For the key nodes,three design wave methods are used to calculate the design wave parameters.The results show that: among the three design wave methods,the long-term forecast design wave method can effectively calculate the design wave parameters of the key nodes.3)Based on the long-term forecast design wave method,perform strength analysis on the key nodes of the platform,and through the investigation of the variable-scale grid method,further study the influence of different welding types on the structural strength of typical cross-node structures.The results show that the structural strength analysis shows that there is obvious stress concentration at the cross joint where the column and the lower pontoon are connected.Under different welding types,the cross joint welding type adopts C-type grinding,which can effectively reduce the stress concentration of the structure.4)Based on the design wave parameters,a simplified spectrum analysis method is used to analyze the fatigue life of key nodes.The influence of different welding types of the cross joint on the fatigue condition is analyzed.The results show that the influence of different hotspot stress interpolation paths on the calculation results is more obvious.The thinner the path plate thickness,the more conservative the calculation results.When the C-type grinding welding process is used at the cross welding joint,the fatigue life of the weldment can be effectively improved,and it is found that the shear force has a great effect on the fatigue damage of the weldment during the investigation. |
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