The Nonlinear Finite Element Analysis On Residual Bearing Capacity Of Tubular T-joints Undergoing Impact

Tubular structures are widely used in offshore platforms,bridges,stadiums and other long-span structures,owing to their aesthetic appearance and cost effectiveness.In recent years,collisions caused by accidents such as earthquakes,explosions,and operational errors have occurred frequently,causing different damage degrees to the tubular structure in the engineering practice and seriously affecting the overall safety of the structure.At present,extensive experiment and numerical analysis on static performance,impact resistance capacity and residual bearing capacity after static damag of the tubular joint have been reported,but the reaserach on residual bearing capacity of tubular T-joints undergoing impact is rare.In this paper,the nonlinear finite element analysis was conduct on the residual bearing capacity of tubuar T-joints undergoing impact loads.Mainly divided into the following work:(1)The ABAQUS finite element software was selected for modeling and analysis,and the Bao-Wierzbicki damage criterion was adopted to simulate the damage evolution of the material.The numerical results were compared with the related curves and failure modes of the axial compression and impact test of the square hollow section(SHS)T-join.The numerical analysis result is within 10%of the bearing capacity error of the axial compression test,and the coefficient of variation is 0.024,while the numerical curves close to the stable section of the impact force and displacement-time history curves.It shows good accuracy in simulating the structural characteristics of SHS T-joints under axial compression and impact load,and can be used for nonlinear finite element analysis on tubular T-joints undergoing impact.(2)Forty finite element models were eatablished to study the failure modes of the SHS T-joint after impact.The research shows that the impact damage is concentrated on the web upper on both sides of the joint,and the impact energy is absorbed by the web buckling and the local concave at the intersection.The impact energy dissipated in the upper flange concave is relatively limited.The compression deformation of the mid-span section caused by the impact is very obvious,and the web has a wavy partial buckling,but the failure mode of the specimen was chaned slightly.(3)The load-displacement curve,impact force and displacement-time history curve obtained by numerical simulation are divided into three stages according to characteristics and described respectively.For the specimens with a larger ratio of brace to chord diameter(β≥0.8),the plane restraint and supporting effect of the brace is stronger than the specimens with a smaller ratio of brace to chord diameter(β<0.8),therefore,this joint have a slight loacl concave and a low sensitivity to impact.(4)The ultimate residual bearing capacity coefficient(ψ)of the joint is defined as the ratio of the ultimate bearing capacity of the impacted joint to the control specimen,the trend of ψ under different parameters was analyzed.It is found that increasing the pre-loaded axial force has a significant negative correlation with the value of ψ,while the larger axial force will aggravate theψ.When the applied axial force is 80%of the ultimate bearing capacity of the control specimen,the ultimate residual bearing capacity of the specimens decreases by 47.17%on average compared with the control specimen.The impact energy has a weaker effect on the ψ value under different parameters than the pre-load axial force,and the impact reduces the average residual bearing capacity of the specimen by 30.61%compared with the control specimen,with the impact energy increases,the ψ value decreases linearly.The β,chord diameter have a obviously positively correlated with ψ,a significantly improved value of residual ultimate bearing capacity can be obtained by increasing any of β,chord diameter values.