Research On Mechanical Properties Of Reinforced Ultra-high Performance Concrete Beams

In recent years,many scholars have devoted themselves to the research of using steel fiber as a measure to strengthen the shear of reinforced concrete beams.It is studied that steel fiber delays the development of critical shear cracks,the possibility of adding a proper amount of steel fiber to replace part of the stirrup to bear the shear force,and the combination of steel fiber and longitudinal reinforcement to obtain better shear and bending mechanical properties.Many scholars have conducted research on ordinary concrete and high-strength concrete beams with appropriate amounts of steel fiber as shear reinforcement measures.There are few similar studies on Ultra-high Performance Concrete(UHPC)beams.UHPC is an ultra-high-strength,high-durability material.In order to promote the application of this material,the mechanical properties of reinforced UHPC beams are studied as follows:(1)An experimental study on the mechanical properties of steel fiber-containing ultra-high performance concrete beams was carried out.Six reinforced UHPC beams were designed with the stirrup ratio and the volume content of steel fiber as parameters,and the possibility of steel fiber substituting some stirrups to bear the shear force was studied through experiments.The test results show that adding a proper amount of steel fiber can replace part of the stirrups to bear the shear force.On this basis,the combined action of the steel fiber and the longitudinal reinforcement can improve the flexural mechanical properties of the beam.(2)Carried out research on the constitutive model of ultra-high performance concrete.The classification summarizes the UHPC uniaxial compression and tensile stress-strain constitutive models proposed by domestic and foreign scholars,and each selects a factor standard to classify them.Select a large number of test curves through quantitative analysis combined with the method of curve trend,compare and analyze the existing models,and propose the optimal UHPC constitutive model under the selected factor standard or propose a new UHPC constitutive model.Apply the proposed conclusions to the simulation study of reinforced UHPC beams in the subsequent chapters,compare the test results to evaluate the proposed UHPC constitutive model,and determine that it has good rationality and applicability.(3)A numerical simulation study of reinforced ultra-high performance concrete beams was carried out.Establish a finite element model of reinforced ultra-high performance concrete beams,select the optimal UHPC constitutive model proposed in the previous chapter,consider the bond-slip relationship between UHPC,steel bars and stirrups,compare the numerical simulation results with the test results,and determine the applicability and accuracy of the proposed model.Parametric analysis of UHPC bending and shear beams can reasonably reflect the failure process and bearing capacity of UHPC bending and shear beams.