Study On The Collision Performance Of Deep Water Offshore Jack-up Platform

With the economic globalization, the population, resources and environment are facing the severe test. Especially with the decrease of land resources, the energy shortage is becoming more and more prominent. The ocean has plenty of oil and gas energy, so it is imperative to enter the era of marine oil and gas. Now, the offshore jack-up platform as the main force, accounting for more than 60% of mobile offshore platforms, and more than 88% of the platforms has been serviced for more than 20 years.In addition, through the analysis of the causes of the offshore platform damage, 31% of the damage is caused by collisions, and each year, about 0.15% of the offshore platforms is subjected to various kinds of collisions and has to stop running for repair. At the same time, the collision accidents will not only bring huge economic losses, but also may cause environmental pollution and casualties.Therefore, it is imperative to construct some new offshore jack-up platforms. And in the design of jack-up platform, evaluating the security is a very important link, because the offshore platform is likely to suffer some accidents and cant not operation normally.This thesis is based on the National Natural Science Foundation of China to study the collision performance of the deep water offshore jack-up platform. Firstly, carried out the benchemark study on nonlinear materials and the drop hammer impact test of the frame structure which to improve the numerical simulation technology, which based on the mechanical property test of ship and ocean structure typical material; Next, carried out the research on modeling technology of offshore jack-up platform collision simulation to solve the problems encountered in the modeling and analysis process and to ensure an accurate and efficient simulation method; Finally, Analysis the performance of collision between ship and offshore jack-up platform, and the collision parameter influence on the crashworthiness of the platform. The main content of this paper is as follows:(1) Determine the typical collision scenario between the ship and offshore jack-up platform based on the statistical accident data and specification requirements.(2) Carried out the benchmark study on ship platform collision nonlinearity simulation. Carried out the benchmark study on the material nonlinear parameters influencing the accuracy of the calculation results based on the typical material quasi static tensile testing result of the typical material, and get the material parameters for simulation which considering the nonlinear effects; then, carry out the drop hammer impact test and the simulation analysis of the frame structure to improve the numerical simulation technology(3) Take the typical nodes of the jack-up platform as the research object, present the “plate-beam” coupling technology for offshore jack-up platform and verify its reliability based on the comparison between “plate – beam” coupling model and shell model. Then, analysis the interaction between the pile legs and foundation to explore the equivalent constraint condition of the jack-up platform. Through compare the collision results of the “pile-soil” coupling model, hinged constraint model and the solidity fixed constraint model, determined the hinge constraint model can satisfied the collision simulation of the large truss stiffened platform.(4) Taking a deepwater offshore jack-up platform as the research object and analyzing the key parameters such as the collision force, deformation and energy absorption in the typical scenario to evaluate its impact performance. The study shows that the platform collision damage has obvious local characteristics and the chord and brace in the collision area with bending instability, which the brace as the main energy absorption component. The failure unit located in the connection position of the horizontal chord and brace.(5) Study the effect of impact parameters on the platform collision performance regularly by changing the impact parameter(such as the impact quality, initial velocity and impact Angle, etc.). The study shows that the impact energy was increased with the increase of impact ship quality and impact velocity, and the damage deformation of collision zone structure is more and more serious; As the impact angle larger, the energy absorption reduce gradually and the platform kinetic energy increase gradually.