Research On Structural Damage Characteristics Of Semi-submersible Lifting Platform Under Falling Accidents

The semi-submersible lifting platform is an indispensable member of the dismantling and lifting operations of marine structures.It has been in a complex and harsh marine environment for a long time.It is difficult to avoid the effects of wind,waves and currents during the lifting process.Personnel make mistakes and are prone to fall accidents.Therefore,it is of great practical significance to study and evaluate the structural safety of semi-submersible lifting platforms during lifting and falling.This paper has made a series of studies on the impact resistance of platform deck structure falling accidents and the reduction of the structural damage,economic loss and environmental damage caused by these accidents.The main research contents are as follows:First of all,the main research status and the basic theory of accident analysis of structural damage analysis under current fall accidents are digested and absorbed.Focusing on the analysis of the research mechanism of the fall accidents and the related standard method accident analysis methods,the research progress of the domestic and foreign scholars on the fall accidents in the experimental method,analytical method,and numerical simulation is summarized.Subsequently,the basic theory of the fall accident analysis was studied,the dynamic analysis theory of the fall model,the nonlinear dynamic finite element theory and the explicit solution method were studied,and the semi-submersible lifting platform finite element was completed Modeling work,including a brief overview of the structural characteristics,determination of the grid size,and the need to simplify the discussion of the structure;based on the platform’s operating characteristics and referring to the relevant regulations,determine the typical working conditions of the platform’s falling scene,and establish the structure of the jacket under the typical working conditions The necessity of parameter setting for typical working conditions is elaborated.Based on the plastic design criteria,the general law of deck structure damage of semi-submersible lifting platform after the jacket fall is studied based on the plastic design criteria.Then,on this basis,in combination with the actual project,refer to the relevant specifications,simplify the falling process,select different types of fall objects(jacket platform deck,container,thin rod)and establish the corresponding finite element model,according to the specifications of the material properties Define it.Determine theparameters of different contact forms,drop height,drop position and angle,etc.,and analyze the sensitivity of the parameters of the damage and deformation,energy conversion and impact force of the deck structure under different drop scenarios.Finally,based on the analysis of typical working conditions and sensitivity analysis,the risk sources of the deck area that may be affected by the fall of heavy objects during the operation of the target platform are sorted out to reduce the risk of falling accidents as much as possible;then to improve the impact resistance,That is,on the basis of the original structure,the optimization of the deck structure is considered from three aspects: structural reinforcement,the addition of a padding anti-collision layer,and the addition of a rubber dressing layer.The local deck model in the previous chapter is the target,using nonlinear finite elements Simulate the difference in response of the deck structure under different measures.