| With the maturity of deep-sea platform development technology,a variety of new structural forms have been derived from semi-submersible platforms,and double-bottom floating body platforms without transverse braces have been applied in offshore operations.In order to ensure that the new platform has sufficient structural strength and safety margin,it is necessary to study the ultimate bearing capacity of the platform structure.In this paper,starting from the local plate frame structure of the platform,the analysis method of ultimate strength is systematically studied.Considering the influence of elements such as element type,element size,material model,nonlinear method,etc.,the finite element model of stiffened plate is used to determine the platform.Calculation method and simulation scheme of ultimate strength,namely quasi-static nonlinear analysis method.Secondly,for a semi-submersible platform without transverse bracing,considering the typical ultimate bearing state in the design specification,through reasonable ultimate load simulation and boundary condition setting,the ultimate bearing capacity calculation of the target platform under various working conditions is completed,and the obtained The calculation result of the ultimate strength of the target platform.Through the structural response analysis,the failure modes and dangerous components of the target platform under different bearing forms are studied,and the response characteristics are summarized by a comparative analysis with the conventional semi-submersible platform in the literature.The calculation and analysis results show that the structural form without transverse bracing has a great influence on the ultimate bearing state of the platform under the condition of transverse waves.Compared with the conventional semi-submersible platform type,the distribution of dangerous structures is significantly different,mainly reflected in the lateral load.,the failure components of the target platform are mainly concentrated in the connection structure between the deck and the column,which is different from the conventional platform transverse bracing as the main dangerous structure;The force load is more sensitive,which is mainly reflected in that when the platform reaches the limit state,the forced displacement of the torque condition is smaller than that of the shear condition.Finally,according to the partial safety factor method proposed in the specification,the deterministic design wave method is used to calculate the design load of the platform under three characteristic states of lateral separation,longitudinal shear and maximum torsion,and the target is verified by comparing with the ultimate bearing capacity.The platform has sufficient strength reserves.This paper takes the new semi-submersible platform without transverse braces as the research object,through the calculation of the ultimate bearing capacity of the target platform and the comparative analysis with the conventional platform,the influence of the structural form design without transverse braces on the overall response of the platform is obtained,and the conclusion is drawn.The response characteristics of the platform without cross braces provide a method basis for the ultimate strength analysis of the new platform,and clarify the dangerous structures that need to be focused on in the design stage of this type of platform,providing a reference for engineering applications. |
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