Flexural Behavior Of Concrete Beams Reinforced With FRP Bars

Fiber reinforced polymer(FRP)bars have the advantages of light weight,high strength,and corrosion resistance.Using FRP bars as reinforcing materials for concrete structures can effectively solve the durability problems of corrosion of steel bars in corrosive environment.However,due to the slastic modulus of FRP bars is lower and the bonding between concrete is poorer,the crack width of FRP bars reinforced concrete beam is larger than that of steel reinforced concrete beams.Therefore,the FRP reinforcement ratio of the beam is generally controlled by the serviceability limit state,which causes a higher cost for FRP bars.In order to reduce the crack width of FRP bars reinforced concrete beam,this paper proposes a new type of construction measure for FRP bars which is fabricated by penetrating the GFRP bars into the metal corrugated pipe and filling the interspace with high strength cement-base grouting materials.The external corrugated pipe only plays the role of forming and strengthening the transmission of the adhesion force,and the outstanding bonding properties of the internal high-strength cement-based grouting material and FRP bars lead to more balanced stress distribution,which reduces the crack width.To verify the feasibility,this paper systematically studies the flexural performance of concrete beams reinforced with extruded FRP bars and the new type FRP bars.The specific contents of the study are as follows:(1)A monotonic loading flexural test was carried out for nine beams reinforced with FRP bars and one with steel bars.The type of FRP bars,the ratio of reinforcement and the adoption of new type of construction measures were taken as the research parameters,the flexural capacity,failure mode and deformability were studied.And the deflection,crack distribution,average crack spacing and crack width under the service load of each test beams were mainly examined.(2)The finite strip method was used to compile the moment-curvature analysis program for FRP bars reinforced concrete beams.The calculation was in good agreement with the experimental results and verified the correctness of the analysis reaults.The parameters analysis was conducted to examine the axial compressive strength of the concrete,the type of FRP longitudinal reinforcement and the ratio of reinforcement at the bottom of the concrete beams,and the ratio of reinforcement of waist reinforcement on the flexural performance of concrete beams with FRP reinforcement.(3)Based on the results of simulation analysis,a calculation formula for predicting the acceptable service load of FRP bars reinforced concrete beams is established through the axis compressive strength of the concrete and ratio of FRP bars reinforcement.