Research On Performance Evaluation Method And FRP Strengthening Technology Of Concrete-filled Steel Tubular Frame Bottom Columns Subjected To Vehicle Impact

As the number of vehicles increases,the probability of vehicle impact frame bottom pillars increases.If the car hits the bottom column,it may be damaged or even destroyed,thereby affecting the function of the frame structure.Therefore,it is significance to study the anti-car crash performance of the frame bottom column.At present,CFST frames are widely used,but there are few studies on the anti-vehicle crash performance of the bottom columns of CFST frames.This paper studies the anti-vehicle crash performance of the bottom column of CFST frame as follows:(1)The bottom column of the CFST frame is designed based on the Chinese and European standards,and the collision process of the bottom column of the CFST frame and the post-collision axial compression process are established.The finite element model was verified by experiments,and numerical simulation was carried out.Based on the damage degree and residual bearing capacity of the post-collision column,the anti-collision performance of the bottom column of the CFST frame was classified and parameterized;(2)The post-collision column was selected.The ratio of the residual deflection in column midheight to the midheight of the column corresponding to the residual bearing capacity is used as the performance evaluation index,and the prediction formula for the ratio of the residual deflection in the column to the height in the column under the impact of the vehicle is given,and the CFST frame based on the residual deformation is established.(3)According to the different performance levels and damage modes of the bottom column of the CFST frame under vehicle impact,the effects of the FRP angles,the number of layers and the reinforcement range on its performance improvement were studied,and corresponding suggestions were proposed.Through the above research,the following conclusions are drawn:(1)There are five performance levels for the bottom column of the CFST frame under vehicle impact,and two damage modes,bending and bending-shear,and the column performance level decreases with the increase of vehicle collision kinetic energy,increases with the increase of the column diameter and the steel tube thickness,and decreases with the increase of the axial pressure ratio of column.(2)The proposed method for evaluating the anti-collision performance based on residual deformation can accurately predict the numerical simulation results,which can be used not only for the review of the anti-collision design of the bottom column of the CFST frame,but also for the performance evaluation of the bottom column of the CFST frame after a car crash.(3)The optimal FRP angles for the bottom column of the CFST frame under the bendingshear and bending damage modes are longitudinal and trasverse directions of the column,respectively.With the increase in the anti-collision performance level of the bottom column of the CFST frame,the number of FRP pasting layers increases,and the reinforcement range is close to the full height reinforcement.