Flexural Behavior And Design Method Of Seawater Sea-sand Concrete Beam Reinforced With FRP-steel Composite Bars

FRP bars reinforced seawater sea-sand concrete structure can effectively slove the issue of corrosion and migitate the shortage of sand,which has broad application prospects in Marine civil engineering.But there is an obvious lack of research on the durability of seawater sand concrete at present.FRP bars have some shortcomings such as low elastic modulus and poor ductility,which can be improved by the composite of FRP and steel.To promote the application of FRPsteel composite bars reinforced seawater sea-sand concrete structure,this paper studies on the mechanical properties and durability of seawater sea-sand high corrosion resistance concrete,the production and tensile properties of FRP-steel composite bars,the bonding behavior between FRP-steel composite bar and seawater sea-sand concrete,the flexural behavior and corresponding design method of FRP-steel composite bars reinforced seawater sea-sand concrete beam.The main elements include:In order to improve the durability of seawater sea-sand concrete,this paper selects a new high-ferric phase cement suitable for marine engineering,and combines it with seawater and sea-sand to produce seawater sea-sand high corrosion resistance concrete.Through the test of compressive strength and the the test of concrete resistance to sulphate attack,the effects of seawater sea sand,high-ferric phase cement and water-cement ratio on the growth of concrete strength and the concrete resistance to sulfate attack were tested.The FRP-steel composite bar was produced and its tensile properties were tested.The stress-strain curve of FRP-steel composite bar was accurately derived by the mixing rule of composite materials.Then bonding behavior between FRPsteel composite bar and seawater sea-sand concrete was tested.The effects of the type of bar,concrete strength and stirrup on the bonding behavior were analyzed from the failure mode,ultimate bonding strength and bonding-slip curve.Four kinds of seawater sea-sand concrete beams reinforced with FRP-steel composite bars with different reinforcement ratios were designed and prepared.Based on the flexural test of beam,the effects of reinforcement ratio on the bending behavior of FRP-steel composite bars reinforced seawater sea-sand concrete beams were studied from the aspects of failure mode,plain section assumption,load-deflection curve,reinforcement strain and crack development.The smart bar was produced by embedding the fiber br agg grating strain sensor in the FRP-steel composite bar,which was tested and analyzed in the flexural test of beam.Based on the test results of the beam flexural test,the design method was analyzed.To ensure the failure mode of FRP-steel composite bars reinforced concrete beam is under-reinforced damage,the calculation formula of the minimum reinforcement ratio and maximum reinforcement ratio of the beam is recommended.The corresponding calculation methods of cracking moment,yi eld bending moment,ultimate bending moment and maximum crack width of under-reinforced beam are proposed,and the design suggestions under different limit conditions are given to provide reference for the formulation of relevant specifications.