Experimental On Flexural Behavior Of Steel Fiber High-Strength Lightweight Aggregate Concrete Beams With GFRP

Compared with the widely used rebar in civil engineering,FRP(Fiber Reinforced Ploymer Rebar)has many characteristics like light weight,low elastic modulus,linear elasticity and corrosion resistance.The work performance of the FRP concrete flexural members under normal conditions is the precondition for the application of FRP to the actual project.High-strength light-weight aggregate concrete has lighter weight,higher durability,better frost resistance,and better thermal insulation than ordinary concrete.However,it has the disadvantages of low elastic modulus and obvious brittleness.The defects of high strength lightweight aggregate concrete can be obviously improved,by adding steel fiber.At present,there is less research on the structure of high strength lightweight aggregate concrete with FRP reinforcement.Therefore,it is necessary to develop the flexural performance of GFRP reinforced lightweight aggregate concrete beams.In order to study the flexural behavior of GFRP reinforced high strength lightweight aggregate concrete beams,10 GFRP reinforced high-strength lightweight aggregate concrete beams were tested.The effects of the type of the longitudinal reinforcement,the ratio of the reinforcement of the GFRP bars,the diameter of the GFRP bar and the incorporation of steel fiber on the mechanical properties of the members were emphatically analyzed.Through the finite element software Abaqus,the finite element model is established to analyze the influence of the strength of lightweight aggregate concrete,the ratio of steel fiber incorporation,the thickness of the protective layer and the section form on the mechanical properties of the flexural members of the high strength lightweight aggregate concrete with GFRP bars.The main contents are as follows:1.The load-displacement curve of the flexural member of the GFRP reinforced high-strength lightweight aggregate concrete is divided into two stages before and after the cracking of the concrete.The curve is bilinear after the cracking of the concrete,and the curve is linear until the concrete is cracked.Under the same conditions,the increase of reinforcement ratio and the addition of steel fiber can reduce the compressive strain and the mid span deflection of concrete under the same load,delay the stiffness degradation and crack development speed,and reduce the maximum crack width under the normal condition.2.The improvement of the concrete strength and adding steel fiber can increase the cracking load and the ultimate load of the component.The increase of concrete strength has a more obvious effect on the ultimate bearing capacity of the component.The effect of cracking load is obvious and the degree of influence on the ultimate bearing capacity of the components is reduced,when the steel fiber reaches above 0.6%.3.Compared with reinforced concrete beams,the high-strength lightweight aggregate concrete beam of GFRP reinforcement should adopt a larger section height to meet the deflection limit under normal condition.This paper suggests that the value of the height to width ratio of the high-strength lightweight aggregate concrete beam of GFRP tendons is 1.25~4.4.According to the deformation coordination relationship,this paper deduces the formula for the height of the boundary pressure zone,the reinforcement ratio of the boundary and the bearing capacity of the normal section for the GFRP high-strength lightweight aggregate concrete beams.The study on the flexural performance of the high strength lightweight aggregate concrete beam with GFRP reinforcement is of great significance for studying the performance of such components,guiding the engineering design and promoting the application of new materials in the engineering.