Experimental Study On Flexural Behavior Of Polypropylene Fiber Reinforced Concrete Beams

Due to the low tensile strength of ordinary concrete materials,the matrix material will quit work quickly after cracking in the tension zone of beam structure,which makes the neutral axis move up rapidly.Moreover,because the cracks can not be effectively controlled,the external corrosion medium will corrode the internal steel bar and cause the durability damage of the structure.Fiber reinforced cement-based materials,due to the bridging effect of internal fibers,can still bear loads after cracking,and effectively control the development of cracks,while showing better deformation capacity and ductility,have become an important product of the increasing demand for concrete performance in modern society.In this paper,the static loading of PP-ECC beam is carried out,and the difference of flexural performance between PP-ECC beam and ordinary reinforced concrete beam is studied.The main contents of the research are as follows:(1)Stage the division of the failure process of PP-ECC beam under bending load.Based on plane section assumption and simplified constitutive structure of PP-ECC material,the calculation model of flexural bearing capacity suitable for PP-ECC beam is established and passed.The test results were verified.(2)Study the crack development law of PP-ECC beam under the step-by-step loading system,including the development mode of crack,the development of crack number,the development of crack width and the development of crack extension height.(3)Under the two loading systems,the development of deformation performance of PP-ECC beam is studied,including the development of overall deformation,the development of maximum deformation,the development of fatigue deformation,the development of anti-damage deformation,the development of deformation recovery capability and the development of ductility.The test results show that the flexural bearing capacity model established by the simplified constitutive model has better precision;when the limit state is reached,the number of cracks and cracks generated by PP-ECC beams are more than ordinary reinforced concrete beams,and the maximum width of cracks And the extension height is smaller than the ordinary reinforced concrete beam,showing better control ability to the crack;under any load,the maximum deformation of the PP-ECC beam is higher than that of the ordinary reinforced concrete beam,and it is more significant in the later stage of loading.The plastic deformation stage;the PP-ECC beam fatigue deformation curve fits well with the original deformation curve under cyclic loading system,and exhibits better damage resistance and deformation recovery ability;PP-ECC when the reinforcement ratio is the same The displacement ductility coefficient of the beam is larger,and the ductility decreases with the increase of the reinforcement ratio.The deformation calculation model based on the effective moment of inertia method has certain precision and can be used in engineering practice calculation.