Influence Of Reinforcement And Steel Fiber On Flexural Performance Of Concrete Beams

With the proposal of the national ocean strategy,the durability of reinforced concrete structures is becoming more and more important,while the new requirements for engineering structures such as high quality and corrosion resistance are put forward.As a new type of building material,FRP(Fiber-Rein Forced Polymer)bars have been gradually applied in practical engineering instead of steel bars due to their light weight,high strength,well corrosion resistance and other characteristics.In combination with steel fiber reinforced high strength concrete with excellent compressive and tensile behavior,FRP bar and steel fiber hybrid reinforced concrete structures are formed to improve the defects of poor bonding performance,large deformation and the like between FRP bars and concrete,improve the deformation resistance of FRP bar concrete structural members under complex environment and load action,and limit crack development.To improve its actual availability and other capabilities,fundamentally solve the problem of steel corrosion of traditional reinforced concrete structures,at the same time,it can improve the mechanical performance of the structure,and improve the safety,applicability and durability of the structure.Based on the flexural tests of 9 FRP reinforced steel fiber reinforced concrete beams,1 FRP reinforced concrete beam and 2 reinforced steel fiber reinforced high strength concrete co MParative beams,this paper studies the effects of steel fiber volume ratio,FRP reinforcement ratio,concrete strength grade and types of reinforcement materials on the flexural performance of FRP reinforced steel fiber reinforced concrete beams.The failure mode and failure mode characteristics,crack development,load-deflection relation curve,ultimate bearing capacity and bearing capacity under normal use,ductility,calculation method of bearing capacity and bearing capacity under normal use,and analysis of flexural bearing capacity of concrete beams under normal use limit state by steel bar and steel fiber under monotonic static action are analyzed.The main research results are as follows:(1)Steel fiber can significantly improve the strengthening and toughening capability of concrete.Meanwhile,the ability of steel fibers to restrict crack development and prevent cracks can effectively reduce the crack width and spacing of specimen beams,delay the stiffness degradation of the specimen beam,and improve its ability to resist deformation under load.(2)Steel fiber and reinforcement can significantly affect the flexural performance of FRP reinforced steel fiber reinforced concrete beams.With the increase of reinforcement ratio,the ultimate flexural bearing capacity and the flexural bearing capacity in the normal service limit state of the specimen beams are respectively increased by 42.2%,65.2% and 21.5%,41.2%.With the increase of steel fiber volume ratio,the ultimate bearing capacity does not increase significantly,but the flexural bearing capacity in the normal service limit state is increased by 26.8%,48.8%,80.1%.At the same time,the addition of steel fiber can effectively improve the beam ductility of the specimen,delay the damage process,and improve the predictability and safety of the structure.(3)Based on the test results,the flexural bearing capacity calculation model of FRP-reinforced steel fiber concrete beams is established,and the influence coefficient of steel fiber and reinforcement ratio on flexural bearing capacity of FRP-reinforced steel fiber concrete beams under normal service limit state is introduced.(4)Based on the calculation method of stiffness analysis method and bond slip theory under the limit of deformation and cracks under normal use limit bearing capacity,based on the calculation model to further analyze the reinforcement material and steel fiber FRP steel fiber reinforced concrete beam under different reinforcement ratios effective use coefficient of bearing capacity,and FRP steel fiber reinforced concrete beam design recommendations are given.