Research On The Collision Mechanism Between Semi-submersible Ocean Platform And Ice

In recent years,human beings have been constantly surveyed on the polar oil and gas resources,finding that the abundant oil and gas resources are distributed on the offshore continent and it is the potential for exploration.And due to the high tension of land resources,it is becoming more and more urgent for the exploration of polar resources.However,for working in this environment,ice load is an unavoidable factor.With the temperature rise,polar ice areas shrinking and floating ice increasing will inevitably lead to the marine structures damage and reduce the life cycle.To sum up,studying the semi-submersible offshore platform operating in the deep sea to reduce the damage by ice load has important significance.In view of the above reasons,this paper researches the collision damage performance between the offshore platform and the ice floe by ANSYS/LS-DYNA,a finite element analysis software.The main contents are as follows:(1)Polar ice is a very kind complex material,and different failure modes have different effects on structural damage.Based on the von-mises yield theory,the ice material is established by using the elastic-plastic material model.It is verified the rationality of the failure process to the ice floe by vertical structure in numerical simulation.The failure phenomenon and form of the ice floe and the stress transfer characteristics in the whole process are analyzed concretely,getting the ice force time history curve.In addition,this paper studies the influence of the ice force value caused by the external factors—the loading rate and the ice thickness.(2)this paper numerical simulated the collision impact between the whole offshore platform(mainly platform column)and the ice floe.In a condition,it is not only analyzing the damage deformation mode of the column outer panel,the transverse frame and an outer plate shape T,but also knowing the change rule to the stress and strain of the element.What is more,the process of the collision impact is analyzed concretely form the absorption energy about the floating ice and the column structure and the force curve of the column structure.Considering the two factors of the initial energy and the collision angle,the damage of the platform column is compared in terms of the energy absorption ratio of each structure and the conversion rate of the collision energy.(3)Talking into account the real environment(fluid),this paper numerical simulated the damage of the platform column in fluid-structure interaction with the ALE algorithm by LS-DYNA,analyzed the distribution characteristics of the flow velocity in different cross and the changes of the flow kinetic energy in the impact process.Then,the two numerical simulations are compared in the damage deformation of the platform column,the absorption energy of the column structure and the impact force,discussing the influence of fluid medium on the collision between platform and ice floe.The analysis shows that: a)the ice floes subjected to vertical structure mainly generated in crushing failure and non-simultaneous failure;b)offshore platform bear the main deformation under the action of ice floe collision and the most serious damage is the column outer panel;c)fluid medium can weaken the damage of platform and accelerate the destruction of ice floes in collisions,but it is more likely to cause structural vibration.