Research On Bond Behavior Between Gfrp Reinforcement And Concrete Based On Distributed Optical Fiber Sensing Technology

Fiber reinforced composite material(FRP)is considered to be a possible replacement of steel reinforcement and thus fundamentally solve the durability problem of reinforced concrete structures because of its low density,corrosion resistance and high tensile strength.The fiber types of FRP bars include glass,carbon,aramidron,basalt and hybrid fiber,so the corresponding FRP can be divided into GFRP,CFRP,AFRP,BFRP and HFRP.Among them,GFRP bars have the advantages of cheap price,high natural vibration frequency is not easy to resonance with the external load in the early stage and low stress relaxation rate in the FRP bar concrete structure has a very common application.In order to give full play to the high tensile strength of GFRP bars and ensure that they share the load with concrete,they must have a reliable bond.However,this research is still not sufficient at home and abroad,especially the lack of research on the local bonding properties of the bonding interface,distributed fiber sensing technology can theoretically measure the bonding properties of each point along the GFRP bar bonding section.Therefore,in this paper,100 drawing specimens were made with reference to China’s GB50152-92,Japan’s JSCEE531 and the American ACI440.3R standards,and the bonding performance of GFRP bars was systematically studied based on distributed optical fiber sensing technology.This paper mainly has two aspects:(1)The τ-s curves of the two are obtained through the experiment,and the failure process,failure mode,bond failure mechanism and bond-slip curve characteristics are analyzed and compared with those of the reinforced concrete specimen under the same working condition.According to the test results,several factors,such as surface structure type of GFRP bars,concrete type and relative position of stirrups and longitudinal bars,which affect the bonding performance of GFRP bars are analyzed.The results show that: 1)in ordinary concrete specimens,stirrups can significantly affect the bond performance of GFRP bars,2# stirrups can significantly improve the bond performance of specimens,the maximum bond strength can be increased to 1.67 times that of the specimen without stirrups,1# stirrups and 3# stirrups weaken the bond performance,the minimum bond strength is only 51% of that of the specimen without stirrups.At the same time,stirrup has little effect on reinforcement.2)In UHPC specimens,stirrups have a weak effect on the bonding performance of GFRP bars,mainly because UHPC has a strong effect on the bars,and stirrups cannot improve the bonding performance.3)in the ordinary concrete bond performance from good to bad in turn is to the rib around the rib,one-way around the rib,reinforcement,peeling groove and sandblasting bars;However,in UHPC specimens,the bond performance of GFRP bars from excellent to poor is in the order of unidirectional ribwound bars,peeled grooves bars,bidirectional rib-wound bars and sandblasting bars.(2)and distributed optical fiber sensing technology based on drawing test data get along the GFRP bond length on the uniform distribution of 8 efficient point bond slip curve,the results showed that every effective point of bond slip curve showed obvious three linear and free end(or load)slip and macro average bond stress curve of the measurement results are obviously different.Based on the bond-slip data of effective points,a bond-slip tri-linear model of GFRP bars was established,and a design proposal for calculating the anchorage length of GFRP bars was proposed.