Experimental Research And Simulation Analysis Of Concrete-filled Double Skin Metal Tubular Jacket Leg Members Under Impact Load

The jacket offshore platform is in a complex and harsh marine environment,and the ice load in winter has caused a serious threat to the platform.The main component bearing the ice load is the jacket leg in the jacket offshore platform structure.The ice resistance of the jacket leg is very important for the safety and stability of the whole structure.In order to ensure that the jacket legs will not fail seriously under the impact of ice load,this paper proposes a new type of concrete-filled double skin metal tubular jacket leg members,which can improve the impact resistance of the whole jacket offshore platform under the impact of ice load,and increase the reliability and safety of the platform structure.Concrete filled double skins steel tube is a combined member with better performance,which is developed further on the basis of traditional concrete filled steel tubular and use inner steel tube instead of integrant concrete.The members have many advantages such as high carrying capacity,good stiffness for resist bending and small lateral deformation,and they are suitable to be used as the jacket leg in the jacket offshore platform structures,this position will inevitably suffer from the impact of ice load during service,which will affect the reliability and safety of the whole platform.Therefore,the dynamic response caused by the members after impact should be paid attention to.This paper studies the impact resistance of concrete filled double skin tube under transverse impact load with the help of theoretical analysis and experimental research,at the same time,it is proposed that the combined members of stainless steel tube concrete with hollow sandwich and aluminum alloy tube concrete with hollow sandwich are new concrete filled double skins metal tubes.The main difference with traditional concrete filled double skin tube is that the outer steel tube is made of stainless steel and aluminum alloy respectively,and the difference in impact resistance between new concrete filled double skins metal tube and concrete filled double skin tube is compared.The main researches is as following:Firstly,the dynamic response test of concrete filled double skins metal tube under transverse impact load was done with the drop hammer rig,the single impact and continuous impact are used in the test,the test mainly studied the stress and failure modes of combined members after impact,the continuous impact is that the impact height and the impact mass remain unchanged for many times until the member is destroyed,small energy multiple impact was also an important index to measure the impact resistance of members,at the same time,it is compared with the impact test results of the hollow tube metal members.The test results show that the plastic deformation of concrete filled double skins metal tube is fully developed under the lateral impact load,and the impact resistance is good;the ultimate energy of the stainless steel combined members is the highest under single impact,and the loading times under the same energy and multiple impacts are the most,so the impact resistance of the stainless steel combined members is more excellent.Secondly,by using finite element ABAQUS software,the dynamic response process of the collision of concrete filled double skins metal tube with fixed ends was simulated,and the numerical simulation analysis was utilized to consider the parameters of the effect of strain rate,contact properties and boundary condition,the relevant data curve was calculated and compared with the test results to verify the accuracy of the finite element model.Thirdly,based on the finite element analysis model,the working mechanism of concrete filled double skins metal tube under lateral impact load was analyzed,and other parameters that affect the impact resistance of members were analyzed,the parameters of analysis include:concrete strength,slenderness,boundary condition,concrete filled steel tube of different cross sections,the ratio of inner diameter and outer diameter of the member.The results of parameter analysis show that slenderness ratio and boundary conditions have the most significant influence on the impact resistance of concrete filled double skins metal tube.The ratio of inner diameter and outer diameter of concrete filled double skins metal tube should not be greater than 0.8,and the hollow ratio of the members reaches 84.4%,and the impact resistance of the combined members declines.