Structural Strength Assessment And Design Optimization Of Asymmetric Semi-Submersible Platform

The development of marine resources needs a kind of auxiliary platforms focusing on fulltime operations such as installation and disassembly onsite.In order to arrange double-cranes on the one side of the platform,different sizes and dimensions are adopted on both sides in the design.As an unconventional structure type,it is necessary to work out load analysis and strength evaluation of asymmetric main structure of platform for ensuring operation safety and layout optimization.In this paper,the wave load and structural response of asymmetric semisubmersible dismantling platform under operating and survival conditions are analyzed,the distribution characteristics of overall and local strength of such platform are summarized,and the optimum measures for improving structural design are discussed from the point of view of structural load balance,in order to provide meaningful reference for the design and development of such platform.The main work and conclusions of this paper are as follows:(1)This paper takes an asymmetric semi-submerged disassembly platform as the research object,reasonably simulates the main structure and auxiliary facilities,determines the unit type,grid division,mass distribution,boundary setting of the platform,and establishes a complete structure model.(2)The whole wave load of the platform is analyzed by the hydrodynamic model,and the three-dimensional potential flow software is used to calculate the load transfer functions of the platform under various typical load-carrying states of operating and living conditions,the design wave parameters are determined,and the wave load characteristics caused by asymmetric structure are analyzed in depth.It is found that under the condition of transverse separation under survival conditions,the maximum load of the platform when the wave propagates against the main side(crane side)of the platform is greater than that when the wave propagates against the auxiliary side.due to different structural dimensions on the left and right sides of the platform.(3)According to the selected design wave parameters,the wet surface of the platform is loaded,the structural response of the platform is calculated,and the structural strength characteristics of asymmetric platform are summarized through the overall strength and the local strength analysis of platform.It is found that the stress on the main side of the platform is high,which is more obvious under operating conditions.At the joint between the column and the pontoon,the longitudinal bulkhead rib in the main pontoon has local high stress area.At the connection between the column and deck,a locally high stress area occurs in the transition area with large rounded corners between the column and deck.In addition,the balance of bearing efficiency of main and auxiliary structures is analyzed from load,yield strength and buckling strength of pontoon and column.(4)For the design of the pontoon structure,the layout schemes of different longitudinal aggregate spacing,plate thickness and stiffener size are discussed.The better design scheme is determined by strength analysis and the comprehensive verification of the scheme is completed by comparing the buckling strength.