Research On The Bonding Properties Of GFRP Bars And Ultra-high Performance Concrete（UHPC）

Reinforced concrete structure is the most widely used structure in modern engineering and has many advantages.However,due to the characteristics of steel and concrete structure materials themselves and the use of environment,the traditional reinforced concrete structure is prone to durability problems.The main reason for durability failure of concrete structure is steel corrosion,which will lead to cracking and spalling of concrete and reduce the bearing capacity of the structure.Therefore,the FRP bars with high strength,low weight and corrosion resistance and UHPC with high strength,good ductility and high impact resistance can be combined to form a new type of concrete structure instead of reinforced concrete structure to solve the problems of insufficient bearing capacity and poor durability of traditional reinforced concrete structures.One of the preconditions for FRP bars and UHPC to work together is that they have good bonding and anchoring performance and can bear loads together.Therefore,in this thesis,GFRP bars and UHPC components are tested and verified by numerical simulation,so as to provide some reference for the combination of these two materials in practical engineering.The main contents are as follows:First of all,81 center drawing specimens with side length of 150 mm were made by GFRP bars diameter,surface treatment form,bond length and fiber content as variables.The failure modes and force mechanism of GFRP bars and UHPC drawing specimens were studied.The influence of the above factors on bond slip performance indicators such as bond stress was analyzed.The results show that the damage interface of GFRP bar specimens is on the surface of the bar,and the damage interface of BFRP bar specimens is inside the bar.The bond slip characteristics of ultra-high performance concrete drawing specimens and ordinary concrete drawing specimens are basically the same.When the diameter or bonding length of GFRP bars increases,the ultimate bonding stress of GFRP bars and UHPC specimens decreases.Steel fiber can improve the bonding performance between surface entangled GFRP bars and UHPC to a certain extent.The diameter of GFRP bars is the most significant factor affecting the bond performance of GFRP bars and UHPC by 24 orthogonal specimens.Secondly,based on the central drawing test data,the existing bond slip models are fitted and compared.On this basis,a constitutive model for GFRP bars and UHPC is proposed,which is in good agreement with experimental results.Combined with the existing design codes,the bond strength is predicted.The results show that the codes are in a safe range when predicting the bond strength in GFRP reinforced ultra-high performance concrete.Finally,the nonlinear spring is used to simulate the bond slip between GFRP reinforcement ultra-high performance concrete in ABAQUS software,which verifies the accuracy of the slip constitutive relationship between GFRP reinforcement and ultra-high performance concrete proposed in this thesis.The stress distribution between GFRP bars and UHPC can be observed by numerical analysis results.The results show that the bond stress between GFRP bars and UHPC shows a law of uneven distribution,and the stress mainly concentrates on the area near the bond interface,and gradually decreases from the loading end to the free end.