Study On Influencing Parameters Of RC Square Columns Confined By CFRP Circumferentially Under Low Velocity Impact

Carbon fiber reinforced composites(CFRP)have been widely used in engineering reinforcement due to their advantages of light weight,high strength,corrosion resistance and durability.The use of CFRP to compress RC columns is a common reinforcement method.However,due to the anisotropic and brittle material properties of the CFRP,the CFRP-reinforced column may cause severe impact damage under the low-speed impact that is not considered by the current specification,resulting in a decrease or even loss of the bearing capacity of the reinforcing column.Therefore,it is of great engineering value and theoretical significance to study the dynamic response of CFRP-reinforced RC column under low velocity impact and the residual bearing capacity of the column after impact damage.Main research contents of this article are as follows:Firstly,the exploratory experiment of CFRP reinforced concrete column under low velocity impact was designed and completed,and the corresponding explicit finite element model was established by finite element analysis software LS-DYNA.The results show that the contact time-history curve obtained by simulation calculation is basically consistent with the experimental results,and the calculated impact damage is also consistent with the experimental results,indicating that the simulation analysis method used in this paper can reflect the transient of CFRP-reinforced column under low-speed impact.State mechanical behavior.Furthermore,the impact damage of CFRP-reinforced RC square column under impact is systematically simulated.The impact response characteristics of the contact force time history curve,energy transfer and stress distribution of the test piece are obtained.The effect of initial hammer speed,CFRP reinforcement thickness and ram shape on CFRP-reinforced RC square column impact damage.The results show that the initial velocity of the ram is the most direct factor affecting the dynamic response and impact damage of CFRP-reinforced columns subjected to low-speed impact.With the increase of CFRP reinforcement thickness,the impact damage of concrete decreases,indicating that CFRP has certain stability to the reinforced column itself.The degree of protection;and the shape of the ram is a key factor in controlling the mechanical behavior of the contact surface.Based on the explicit-implicit continuous solution method,ANSYS implicit finite element software was used to simulate the axial compression process of CFRP-reinforced RC square column after impact damage,and the crack development process,load-displacement curve and stress distribution of the specimen were obtained.The finite element results were compared and analyzed.The effects of different initial hammer speeds and different CFRP reinforcement thicknesses on the residual bearing capacity of CFRP-reinforced RC square columns after impact damage were analyzed.The results show that when the impact damage of the CFRP reinforced column is small,the residual bearing capacity has been reduced to a large extent.