Study On Residual Bearing Capacity And Damage Of Concrete-Filled Circular Steel Tube Columns Under Lateral Impact

Due to the interaction between steel tube and core concrete,concrete-filled steel tube(CFST)has superior mechanical properties,which meets the needs of modern engineering structure to the development of long span,high rise and heavy load.It is widely used in super high-rise,bridges and other structures.In addition to the design load,it may be subjected to impact load during its service,which may cause structural damage or even serious damage,resulting in loss of bearing capacity and collapse,which seriously endangers the safety of personal and property.Therefore,it is of great significance to carry out research on the dynamic response,residual bearing capacity and damage of circular CFST columns under lateral impact,which can provide a useful reference for the impact resistance design of CFST structures.In this paper,ABAQUS software is used to study the lateral impact of circular CFST columns as follows :(1)The lateral impact model of circular CFST column is established and verified with the existing drop weight impact tests.Considering the strain rate effect and mutual contact relationship between steel and concrete under dynamic load.The influence of axial force is considered and the residual bearing capacity of the damaged column is calculated through the method of mutual conversion of Standard analysis and Explicit analysis.The finite element simulation is verified by the hourglass energy control and the use of the existing CFST columns drop hammer impact test data.The test verification includes the failure mode,impact force and displacement time history curve.The proportion of hourglass energy is less than 10%,and the test are in good agreement with the finite element analysis results.The results show that the finite element model established in this paper can accurately and effectively simulate the mechanical properties of circular CFST columns under lateral impact load.(2)The mechanical properties and residual bearing capacity of circular CFST columns under lateral impact are analyzed.The analysis content includes the whole process analysis of dynamic response,stress and strain state,and the residual bearing capacity of the circular CFST columns.Discuss the energy conversion,stress-strain growth of the circular CFST column under lateral impact load,and the acquisition and calculation of the remaining bearing capacity of the column after impact damage.The analysis results show that the circular CFST columns have good impact resistance.(3)The main parameters that affect the dynamic response and residual bearing capacity of the circular CFST columns under lateral impact are analyzed.The influence parameters include impact energy,constraint effect coefficient,the length to diameter ratio,axial compression ratio,impact position,etc.Analyze the influence of each influencing parameter on the impact force,displacement and residual bearing capacity,and obtain the function relationship between the displacement and residual bearing capacity of the impacted column and the five influence parameters through regression analysis and fitting.The coefficient of determination and the coefficient of complex determination of the fitting function formula are both close to 1,it shows that the high fitting accuracy and the five influence parameters analyzed are the main influence parameters.(4)Divide the damage assessment grade of the circular CFST column and establish the damage grade assessment curve.According to the material damage state,deformation and residual bearing capacity of the circular CFST columns after impact damage,it is divided into four damage levels: mild damage,moderate damage,severe damage and damage failure.Based on the two evaluation indicators of maximum displacement and residual bearing capacity,a damage grade evaluation curve with impact quality and impact speed as the main control parameters is established.According to the position of the damage assessment curve where the combined point of impact quality and speed is located,the damage grade of the damaged circular CFST column can be quickly determined.