Finite Element Analysis On The Flexural Toughness Of Hybrid Fiber Reinforced Concrete

The toughness of fiber concrete is the ability to maintain large material deformation after cracking,and it can maintain the strength of material.The improvement of this property is more important than that of strength improvement under many application conditions.The existing methods of bending toughness both at home and abroad are controlled by the cross-middle deflection,but the direction of fracture expansion is the same as that of deflection.When the mid span deflection is used to control the test,especially for the concrete with low fiber content,it is easy to lose stability in the softening section of the test and can not get the complete softening section curve.Therefore,it is of great practical value to explore the evaluation method for flexural toughness of low content hybrid fiber reinforced concrete considering comprehensively the operation process and evaluation index.Based on the finite element analysis and linear fitting method,the flexural toughness evaluation method based on load crack opening displacement curve is studied based on the completed flexural toughness test of notched beam.The main work of this paper is as follows:(1)The modeling program of fiber unit in Grasshopper is written in Python language,and the random uniform distribution of the hybrid fiber is realized.(2)Working together in the ANSYS using the constraint equations of fiber and concrete realization of the two kinds of materials,with the method of reasonable division of load steps to solve nonlinear problems caused by the material nonlinearity of concrete significantly,the separate finite element analysis model,the constitutive relation of concrete,steel fiber,steel fiber and polypropylene monofilament fiber separately.(3)The finite element analysis of cube compressive strength as pre notched beam bending toughness of finite element analysis,by comparing the cube test values and test values of finite element analysis of crack development in the test process and its final failure form and the compressive strength of the simulation,verify the rationality of the finite element analysis of each step.(4)Further analysis of the flexural toughness of notched beam test data,the linear fitting method given deflection and crack notch beam mouth bilinear displacement,explore the feasibility of flexural toughness evaluation method of load crack mouth opening displacement curve based on the definition of toughness;closely,the toughness index and after cracking the residual flexural toughness index as evaluation index of flexural toughness of notched beam method.(5)The finite element analysis method is used to increase the analysis samples and further excavate the role of "micro reinforcement" of the plastic steel fiber.It is shown that the best hybrid fiber ratio can give full play to the role of "micro reinforcement" of the plastic steel fiber under the condition that the volume of the total volume is no more than 1%.