Study On Flexural Behavior Of Reinforced Concrete Beams With GFRP Bars And Reinforcement

The corrosion problem of steel has not been effectively solved.With fiber reinforced polymer bar(FRP band)come out,scholars try to use the FRP bar to solve this problem.However,the low elastic modulus,linear strain characteristics lead to cracks and deflections of fiber reinforced concrete beams,which is one of an important reason for its extensive development in the project.In this paper,GFRP tendons are used instead of part of the steel bars to form mixed reinforced concrete beams.The bending behavior of mixed reinforced concrete beams was analyzed by a series of experiments,such as GFRP tendons,concrete test pieces and three kinds of concrete beams were fabricated.Combined with theoretical research and then put forward the following conclusions;(1)As the surface hardness of GFRP tendons is low,the elastic modulus is small and so on,its bond strength with concrete is slightly lower than that of steel.It is suggested that the bond strength between steel and concrete is about 1.3 times that of fiber.(2)In this paper,a new type of anchor is proposed to increase the bond between the reinforcement and the concrete.It is suggested that the anchoring length is 14 d.At the same time,the basic anchoring formula of the end anchor is proposed,which is convenient for the follow-up theoretical research.(3)The cross section of the hybrid reinforced concrete beam conforms to the flat section assumption.The four stages of the load-deflection curve are essentially linear.The load-deflection curve of GFRP tendons is divided into two stages,the deflection and crack of the beam are suddenly increased after cracking.After unloading,the recovery capacity of GFRP reinforced concrete beam is the best(4)The development mechanism of the three kinds of beams cracks is similar,and the load-fracturecurve is basically parallel.Deriving a simplified expression of cracking moment of hybrid reinforcement beam.After unloading,the recovery ability of the cracks of GFRP tendons is the strongest.(5)Based on the test and theoretical analysis,the expression of the ultimate bending moment of the composite beam under the condition of less reinforcement,reinforcement and super reinforcement is derived,which can be applied to engineering practice.