Experimental Study On The Effect Of The Outer Layer On The Low-speed Impact Performance Of CFRP Reinforced Square Columns

In recent years,there have been frequent traffic accidents at home and abroad,and the number of terrorist attacks has gradually increased.Whether the reinforced concrete structure meets the requirements of building codes after being damaged by low-speed impact,and how to carry out targeted reinforcement and reinforcement.These problems make various engineering structures suffer from low-speed impact.Mechanical properties have become the current research hotspot.Carbon fiber reinforced composite materials(CFRP)have the advantages of light weight,high strength,corrosion resistance,etc.,and are widely used in the reinforcement of various types of concrete components,such as bridge piers and viaduct load-bearing columns.In recent years,there have been in-depth studies on the impact resistance of CFRP hoop-bundle reinforced concrete structures,but there are still many gaps in the impact resistance of CFRP hoop-bundle reinforced specimens under the protection of the external layer,especially at high altitudes and low speeds.Research on the remaining bearing capacity of CFRP reinforced columns under impact.This paper systematically studies the impact of different external layers on the mechanical properties of CFRP-reinforced large-scale square columns under low-velocity impact through low-speed impact and axial compression tests,which has practical engineering significance in improving the safety performance of CFRP-reinforced structures.The main work of this paper is as follows:(1)Explain in detail the structural characteristics of large-scale concrete square columns reinforced with three different external layers of CFRP,and introduce the experimental design of high-altitude and low-speed drop hammer impact and axial compression of damaged specimens.(2)Using the same quality hammerhead to carry out multiple impact tests on large-scale square columns reinforced by CFRP protected by different materials with external layers from the same height,by analyzing the local damage image,contact force time history curve and contact force time history curve of the specimen after impact damage.The dynamic response process is to explore the influence of different external layers on the impact resistance of CFRP-reinforced concrete columns.The ring-to-bundle effect of the three external layers improves the stiffness and impact resistance of the CFRP-reinforced specimens to varying degrees.From large to small,they are bidirectional basalt fiber,unidirectional basalt fiber,and glass fiber.(3)Conduct axial compression test on the impact-damaged specimens.By analyzing the failure phenomenon of axial compression test,the residual bearing capacity loading curve and the strain development of key positions,explore the effect of different external layer materials on the remaining CFRP ring-bound reinforcement column Bearing capacity impact.The remaining bearing capacity of the three external CFRP reinforced specimens is different.Because the fiber bundles are divided into warp and weft directions,the two-way basalt fiber has the strongest protective effect and the largest ultimate remaining bearing capacity.