Study On Anchorage System Of CFRP Tendon For Reinforcement

As China's construction market is becoming increasingly saturated,people's demand is reduced,new buildings will gradually decrease,and the repair and reinforcement work of existing buildings will gradually increase.Carbon fiber reinforced polymer(CFRP)is widely used in the field of building reinforcement due to its high strength and corrosion resistance.Its elastic modulus is similar to that of steel bars.The "ordinary surface sticking method" has limited effect on reducing the deflection and cracks of members.Prestressing carbon fiber can solve this problem,while improving the bearing capacity of the component,it can effectively improve its normal service performance.It is early to start using CFRP plate and relative technology is more mature.However,when the size of reinforced component is small,CFRP plate reinforcement will be limited by size.In this paper,CFRP reinforcement is used as reinforcement material,and it is anchored with a bond anchor.The influence of the anchorage length and the inclination angle of the anchorage wall on the anchorage performance of the anchorage is taken as the main point,and the relevant parameters of the anchorage are preliminarily determined through the literature of the relevant scholars.After that,the anchorage performance of the test anchorage is studied through static test.The influence of anchorage length and the inclination angle of the anchorage on the anchorage performance of the anchorage is determined.Based on the regression analysis of the test results,we get the bond-slip constitutive relation model,the average bond strength formula and the ultimate anchorage length of the anchorage.At the same time,in order to realize the feasibility of anchorage in practical application,in the fifth chapter of the article,the prestress loss analysis of the test anchorage is analyzed,and the accuracy of the derivation formula is determined by combining the prestress loss test.According to the static test of CFRP bar anchorage,it is found that the influence of anchorage length and inclination angle of anchorage on anchorage performance of anchorage is as follows: 1.With the increase of anchorage length(less than the ultimate anchorage length)and the inclination of the inner wall of the anchorage,the ultimate failure load and average bond strength of the anchorage are improved;2.The ultimate anchorage length corresponding to the CFRP bar with the same physical parameters is fixed value.When the anchorage length is greater than the limit anchorage length,the average bond strength will decrease;3.The increase of the inclination angle of the anchorage will increase the constraint effect of the wedge of the oxygen mortar on the CFRP bar,which is not affected by the performance of the CFRP bar itself;4.The bond-slip constitutive relation of anchorage shows attenuation wave change;5.With the increase of the anchorage length and the inclination angle of the anchorage,the crest value and the corresponding slip amount of the bond-slip constitutive relation increase;6.The prestress loss items of the test anchorage include: Deformation of anchorage and prestress loss caused by shrinkage of CFRP bars;Prestress loss caused by stress relaxation of CFRP tendons;Prestressing loss caused by shrinkage and creep caused by prestressing and environmental factors;Prestressing loss caused by concrete compression due to prestressed action;Prestress loss due to slippage of CFRP bars relative to bonded materials;Prestress loss caused by creep of anchorage material;The loss of prestress caused by temperature.The main innovations of this paper are as follows: 1.A CFRP reinforcement anchorage system suitable for building reinforcement is studied.According to the test results,a set of bond slip constitutive relation model between CFRP reinforcement and epoxy mortar is fitted.At the same time,limit anchorage length and a set of formulas for calculating the average bonding strength for test anchorage is derived by reference model and related theory.These are measures to help test anchorages to be popularized in practical application.2.According to the norms and the books of the relevant scholars,the formula for calculating the prestress loss for the anchorage of this test is summarized,and it is verified according to the prestress loss test.