Study On Tubular K-joint With Preloaded Axial Tension On Chord Under Impact Loadings

Accidental loads from time to time have an impact on offshore platforms in practical engineering.As an important component of the tubular truss,the tubular joints will inevitably lead to the reduction of the working performance of the tubular truss when the tubular joints are impacted.In serious cases,the entire offshore platform will be destroyed.Corrosion,residual stress and the axial forces on the tubular joints based on other factors are not taken into account.In actual practices,under the effect of self-weight,equipment,etc,the tubular joint itself is subjected to a certain axial force in most circumstances,which makes its stress situation more complicated.Our research team has separately researched the corresponding stress situation.This paper analyzes the impact resistance of K-joints under the condition that the chord member is subjected to axial tension.In this paper,the impact resistance of K-joints under axial tension is analyzed,which includes the following parts:(1)The impact test of K-joints is conducted when the chord member is subjected to axial tension.Firstly,the material characteristics of steel are obtained to prepare for modeling.Secondly,the design of the test plan and the specimen is carried out,mainly including the geometric size of the specimen,the measurement plan,the installation of the specimen,the load application and the data acquisition.Thirdly,the specimen after the test are photographed and compared,and the residual deformation and failure modes of the components are compared and analyzed.Finally,strain,impact force,displacement,and other data are extracted from the test data,and the above data are analyzed by corresponding time history analysis and energy dissipation analysis.The failure mode of each specimen under different stress states of the chord member and the bracing memeber is obtained through experiments.(2)The data calculated by finite element software ABAQUS are compared with the test data.The model simplification,material properties,element selection and meshing,analysis step setting,interface contact,boundary conditions,load application,and other aspects are introduced respectively.Finally,the simulated failure mode,impact force,displacement,and other aspects are compared with the test data to verify whether the model results are consistent with the test results.And prepare for the work mechanism analysis of this joint.(3)The impact resistance working mechanism of pre-stretched K-joints is analyzed.The finite element software ABAQUS is used to calculate the determination of the stable bearing capacity,deformation law and energy dissipation of K-joints during impact resistance.(4)The impact resistance parameters of pre-stretched K-joints are analyzed.Geometric parameters include the diameter-thickness ratio of the chord member,the thickness ratio of the chord member and bracing member,load parameters are axial stretch ratio and initial impact speed.By changing the parameters' values,the effects of different parameters on shock resistance of K-joints are studied,and their influences on the variation laws of joint bearing capacity and plastic deformation are determined.(5)The outlook is summarized.This study only takes account of the effect of axial tension on K-joints and does not consider the influence of other factors.It has certain limitations.Therefore,other research directions on impact resistance of tubular joints are summarized.