Study On Fatigue Property Of The Interface Of Bonding Anchorage System For CFRP Tendon

Carbon fiber reinforced polymer(CFRP)due to its excellent performance,such as light weight,high strength,fatigue resistance and corrosion resistance,it has huge potential application value in the bridge engineering.Using CFRP cable instead of wire rope is expected to solve the problems of wire corrosion,big heavy and other issues.Due its poor lateral performance,the anchoring system of the prestressed CFRP tendon cannot be used in the traditional anchoring mode of steel cable,otherwise It will cause shear failure of the CFRP tendon,and the anchoring system will fail in advance.At present,many kinds of anchorages have been developed,among which,the bond-type anchorage can better protect the CFRP tendon,while the existence of adhesive interface in the bond anchorage system will causes bond slip failure of anchorage system,thus the anchorage efficiency is reduced.Therefore,studying the interface characteristics of the adhesive CFRP anchorage system,especially studying the interfacial fatigue characteristics and the bond damage mechanism of the interface and to improve the bond performance of the anchorage system is of great significance to improve the working performance of the anchorage system and the anchorage efficiency.Based on the national natural science foundation project(Project ID: 51508235 and 51608234),the natural science foundation project of the education department of jiangsu province(Project ID :17KJD580002),the main contents and results of this study are as follows:1.Static load test of the adhesive anchorage system for CFRP tendonThe anchoring effect of inner cone anchorage with different internal parameter is studied,and based on the experimental results,a suitable internal cone type bonding type is selected to make the fatigue specimen.The anchoring properties of the adhesive system under different interface treatment modes are tested and the influence of interface weakening degree on system anchoring performance is analyzed.Based on the test results,the following conclusions are drawn:(1)The increase of the inclination of the inner cone of the anchorage is helpful to improve the anchorage performance.With the increase of angle of the inner cone,the anchorage effect of the system is also improved to a certain extent.(2)Sand adhering to the surface of the CFRP tendon will increase the roughness of CFRP tendon-medium interface,however,the high content of sand grains reduces the bonding performance of the interface.(3)With the increasing of the strain gages on the surface of CFRP tendon in the anchorage zone,the degree of the weakness of the interfacial bond performance tends to be larger,at the same time,the anchoring performance of the system is worse.2.Experimental study on interface fatigue performanceAccording to the results of static load test,the cohesive anchor with specific parameters and structure is selected to make fatigue specimens,and a series of tests with different parameters were carried out on them,through that,the variation of slip value and the temperature of the tendon-medium interface were researched.Based on the experimental results,the following conclusions are drawn:(1)When the stress amplitude is within a certain range With the increasing of cycles,the slip of CFRP tendon-medium interface increases gradually while the amplitude of that decreases gradually,the anchorage system tends to be stable.After the cycles reach a certain number,the slip value no longer increases and the system will enter into a stable state.(2)The loading frequency has great influence on the interface temperature,When the frequency is low,the interface temperature gradually increases and reaches stability.When that is high,the interface temperature rises first and then decreases gradually until it reaches stability.The variation of temperature is consistent with the interface slip to some extent,which reflects the working state of anchoring system.3.Interface fatigue damage of the anchorage systemIn this paper,the adhesive mechanism of the interface between CFRP tendon and the medium is analyzed,through cyclic loading test,the fatigue properties of the interface between CFRP tendon and medium(the variation of temperature and interface slip)is studied.Upon the test data of that,the interface fatigue properties of the anchorage system is analyzed by using shear tube geometry model.At last,this paper points out the deficiencies in the research and application of the anchorage system for CFRP tendon.Combined with the development of bridge engineering in today’s world,this paper points out that its research and application need to be further improved and provides some suggestions for its anti-fatigue design.