Analysis Of Mechanical Properties Of BFRP-Constrained RC Columns Under Impact Loading

Buildings on streets and underground car parks in cities where there is a high concentration of vehicles are threatened by vehicle impact loads.In underground car parks where space is limited,there is not enough space to arrange impact protection measures.Reinforcing reinforced concrete columns exposed to vehicle impact loads can enhance the impact resistance of the columns and make them less susceptible to damage.This paper aims to study the mechanical properties of reinforced concrete(RC)columns restrained by BFRP sheet under impact load by numerical analysis.Considering the influence of different factors on the mechanical properties of columns,this study will analyze the properties of reinforced concrete columns constrained by BFRP under different impact loads,and compare the mechanical properties of reinforced concrete columns with different parameters under impact loads.In terms of load,impact velocity,punch mass,punch contact area and load position will be considered.Starting from the column itself,considering the influence of the number of BFRP sheet layers,concrete strength,concrete column length and longitudinal bar diameter,observe the stress nemogram of the component,contact force time history curve,displacement time history curve,energy curve after the impact of the column,summarize the relevant data changes,draw a conclusion.This paper studies the mechanical properties of reinforced concrete columns strengthened by BFRP sheet under impact load under different influencing factors:(1)Control the punch speed,load position,punch contact area under the same conditions,change the punch mass,analyze the mid-span displacement,component absorbed energy,contact force time history curve and impact load under the column stress distribution changes in mechanical properties,study the impact of impact load on BFRP constrained reinforced concrete column.The impact of ram speed,load position,punch contact area and other impact loads on the mechanical properties of the composite was studied successively.(2)Under the condition that the column length,diameter of longitudinal reinforcement and concrete strength are the same,the number of BFRP sheet layers is changed to investigate the maximum displacement in span,the energy absorbed by the component,the time history curve of contact force and the stress distribution of the column under the impact load,and the mechanical properties of the composite column under the impact load.The influence of impact load on mechanical properties of composite columns under different working conditions,such as column length,diameter of longitudinal reinforcement and concrete strength,is studied successively.(3)The simulation results show that BFRP sheet protects the surface of concrete,so that the concrete and punch contact place under less stress,indicating that BFRP sheet has a better protection effect on the surface of concrete.(4)The increase of impact kinetic energy has a great impact on the safety of the column.The contact force,mid-span displacement and absorbed energy of the component all increase accordingly,making the component more dangerous.The reduction of the contact area will make the column subject to greater contact force,and the concrete surface of the column is more likely to be broken.When the impact position is close to the support,the maximum displacement of the component will be reduced,and the effect is more obvious when the impact position is close to the fixed support.(5)The increase of column stiffness is easy to make the member bear greater contact force,and the mid-span displacement of the member will decrease accordingly,and the absorption of plastic energy of the member will be weakened but the absorption of elastic energy will be enhanced.