Analysis Of Collision Mechanism And Study On Structural Crashworthiness For Deep-water Drilling Platform

As the basic facilities for the development of offshore oil and gas resources,deepwater drilling platform is in the complex marine environment for a long time,due to navigational operation errors,and the vessels may be disturbed by winds,waves or current when docking,it is difficult to avoid the accidental accident of a ship collision,which is often disastrous.Therefore,it is of great practical significance to study and evaluate the crashworthiness of the deep-water drilling platform.It means that in the stage of platform structure design,collision accidents should be taken into account to improve crashworthiness,so as to minimize the adverse consequences such as structural damage,economic loss and environmental damage caused by these accidents.In this paper,the basic theories of crash accident analysis,including the standard method,the basic theory of collision analysis,and the key technologies of nonlinear finite element analysis,are digested and absorbed.Then,the nonlinear finite element analysis,external dynamics analysis,simplified analytical method and internal dynamics simplified analysis method are applied to analyze the internal and external mechanism of the collision.Accordingly,the general rules related to the crashworthiness of deep-water drilling platform after collision,such as collision characteristics,energy dissipation and structural plastic deformation and energy absorption,are analyzed.On the base of these,a more applicable evaluation process of structural crashworthiness is proposed,which provides a reference for the prediction of crashworthiness and design of crashworthiness structure.The main contents of this paper are as follows:(1)The main research status of structural damage analysis under current collision accidents and the basic theory of accident analysis are digested.At the same time,it is focus on analysis for the key technologies of ship-platform collision analysis methods and related regulations,the basic theory of collision internal and external analysis and the nonlinear finite element analysis.(2)The relationship between mesh size and failure strain of light plate and stiffened plate in numerical analysis is studied,and compared with the corresponding quasi-static penetration test,which can provide reference for determining the mesh size and failure strain value of ship platform impact numerical simulation analysis.On this basis,according to the specification,we determine the main platform collision parameters,complete the finite element modeling of the supply ship and deepwater drilling platform,and confirm the parameters of the material model.(3)By using the nonlinear finite element method,the damage characteristics of the vertical column structure of the deepwater drilling platform after the stern collision of a rigid supply ship are studied.On this basis,the dynamic response of the platform column structure under the impact parameters,such as the impact velocity,the impact position and the impact angle,is compared.In addition,based on Shared-Energy Design Principlal,the collision scene of the elastoplastic ship stern collision elastoplastic platform column is simulated and analyzed.(4)Based on the theory of external dynamics of collision and the calculation method of DNV specification,a new estimation method of dissipative energy,named DNV`R analytical method,is proposed,which can make up for the lack of DNV standard method that is only suitable for collision scenarios.Meanwhile,the existing Zhang analysis method and Liu analysis method based on ship-ship collision are analyzed,and the calculation program for dissipating energy of impact ship is compiled,which is successfully applied to ship platform collision scenario.Finally,the results of the corresponding collision simulation analysis are taken as reference,and the simplified analytical method is compared and analyzed to verify the effectiveness and accuracy of the calculation results.(5)Based on the Ductile Design Principlal,the dangerous scene of the collision between the bow and the platform column is studied.The ship's bow is replaced by rigid sphere and three typical collision locations are analyzed respectively.The numerical results of the corresponding collision position are compared and analyzed to verify the accuracy of the simplified analysis method applied to the prediction of the energy absorption of the structure of the column collided.(6)For the collision structure,a widely applicable structure crashworthiness evaluation process is put forward,and the main steps,the crashworthiness evaluation criteria,the energy dissipation capacity of the impact body and the strain energy absorption calculation method are analyzed in detail.On this basis,two collision avoidance crashworthiness evaluation cases are given for ship platform collision accidents,and compared with the numerical simulation results which are closer to the real collision scenarios.The research content of this paper has a certain guiding significance for the rapid evaluation of collision resistance performance of the collision structure during the collision process of ship platform,and for researching on the design of crashworthiness structure.