| Although CFRP has been widely applied in the reinforced concrete structure strengthening for years,but it is prone to being damaged by impact loads due to the anisotropy.In the real world application,reinforced concrete structures are faced with various impact effects during the process of using.This may decrease the bearing capacity of reinforced columns,which occasionally leads to structure destroyed,or even building collapses.For example,when the bridge pier is hit by a vehicle or the impact of an explosion,the structure collapse and a major accident occurs.Therefore,in the design process of CFRP-reinforced buildings,the stability of the building structure under the impact load should be fully take into account.It has a vital significance to study the dynamic response of CFRP ring beams reinforced columns under low speed impact and the residual bearing capacity of damaged columns.In this paper,a self-made drop hammer test device made by the research group is used to conduct a low-speed impact test on a CFRP ring-girded reinforced concrete square column,and to study its dynamic response under the action of low-speed impact.On top of that,the residual load capacity of a 500 T fourcolumn press was studied.The main research content is as follows:1.Introduce the design and production of test specimens,including concrete and CFRP cloth,steel adhesive for repairing test specimens,primer and surface adhesive for CFRP cloth.In addition,the test equipment and acquisition instruments for impact test and axial pressure test are introduced.2.In the impact test,the initial kinetic energy,the number of CFRP layers,the shape of the drop hammer head,and the impact position were taken as the research objects,and the time history curve of the acceleration of the drop hammer and the time history curve of the support reaction were collected,and photographed with a high-speed camera.The entire impact process.The results of the test have shown that with the increase of the initial kinetic energy,the damage scope of CFRP-reinforced columns increased and the damage is significantly aggravated.Besides,compared with the first-layer CFRP-reinforced specimen,the two-layer CFRPreinforced specimen has a similar damage state and a reduced damage range.The contact force of the shaped hammer head is greater than that of the spherical hammer head.The CFRPreinforced concrete square pillars are impacted on the face and the ribs respectively.Due to the small area of impact on the edges,the specimen is more severely damaged.3 In the axial pressure test,a 500 T four-column press was used to perform an axial pressure test on the damaged column after impact.The test used the approach of displacement loading to generate collected force-displacement curves and stress-strain curves.By observing those two curves and the failure form of the test piece to analyze the impact.The effect of action on the bearing capacity of the test piece.Accordingly,the result demonstrated that the damage of impact-damaged columns starts at the damage site first,and then decreases with the increase of the loading displacement. |
