Study On The Protection Performance Of Outer Cladding On CFRP Circumferential Beam Reinforced Columns Under Different Low-velocity Impact Conditions

The carbon fiber composite material(CFRP)reinforcement method has become the mainstream technology for concrete structure reinforcement.However,due to the anisotropy and brittleness of CFRP materials,the impact effect will lead to a sharp decrease in the reinforcement effect of CFRP materials or even failure,resulting in significant safety hazards of the reinforced structures.There are few studies at home and abroad on the protection of CFRP circumferential beam reinforced columns under impact.Therefore,this paper investigates the impact resistance of adding an outer cladding layer on the surface of CFRP layer by using experimental plus numerical simulation.In this paper,CFRP circumferential beam reinforced reinforced concrete(RC)columns are studied.First,CFRP-reinforced RC columns with external cladding were prepared,and the impact dynamic response and damage characteristics of the reinforced columns were investigated by using the impact test device designed and fabricated by our group.Subsequently,the impact-damaged reinforced cylinders were subjected to axial compression tests using a press to study the effect of impact on their axial compression properties.Based on this,the impact protection effect of the bi-directional glass fiber GFRP outer cladding on the CFRP circumferential bundle reinforced RC cylinders with different parameter settings was further investigated systematically using the finite element simulation analysis method validated by the test results.The studied parameters include impact velocity,concrete strength grade,axial pressure ratio and impact location.In the explicit finite element simulations for the low-velocity impact condition,the mechanical behavior and impact protection performance of CFRP circumferential bundle-reinforced RC cylinders with external cladding were analyzed in the impact velocity condition,taking into account the nonlinearities such as material nonlinearity and contact.It was found that: the use of external cladding can significantly reduce the impact damage of the reinforced cylinder;the impact velocity and concrete strength grade have significant effects on the dynamic response of the reinforced cylindrical specimens;the axial pressure ratio has relatively small effects on the dynamic response of the reinforced cylindrical specimens;the impact location has no significant effect on the dynamic response of the reinforced cylindrical specimens.The axial pressure performance of reinforced cylindrical specimens with different impact damage was investigated by using the explicit-implicit continuum solution method and considering the material nonlinearity problem.It was found that the residual axial compressive capacity and axial deformation capacity of the reinforced cylinders with external cladding were significantly improved under the same impact conditions due to the protective effect of the external cladding material;the impact velocity and concrete strength grade had significant effects on the protective performance of the external cladding;the axial compression ratio had a small effect,while the impact location had no significant effect.