Study On Basic Mechanical Properties And Damage Behavioe Of Steel Fiber Reinforced Concrete

Steel Fiber Reinforced Concrete(SFRC)is widely used in civil engineering because of its high strength,good impact resistance,crack resistance,ductility and durability.The failure of SFRC is very harmful to the stability and safety of engineering in practical applications.Therefore,studying the basic mechanical properties and damage failure behavior of SFRC has important guiding significance for its structural design and application.However,the damage and failure behavior of SFRC is extremely complex,and the research on the damage and failure behavior of this type of material has not been perfected so far.Based on the background,this paper selects copper-plated microwire steel fiber reinforced concrete as the research object,and systematically studies its basic mechanical properties(compressive,splitting tensile and flexural properties)and damage failure behavior through two methods: experimental and numerical simulation.In terms of testing,the compressive tests,splitting tensile tests,flexural tests,and the full-field strain observation tests based on DIC technology were carried out on SFRC to obtain the compressive strength,splitting tensile strength,flexural strength and failure characteristics of SFRC.In terms of simulation,the two-phase meso-finite element model of SFRC was established based on ABAQUS,and the rationality of the modeling method is verified by numerical simulation of the aforementioned three strength tests.On this basis,the models were used to study the factors affecting the mechanical properties of SFRC.The main contents and conclusions of the research are as follows:(1)The copper-coated microwire steel fiber concrete specimens with different volume content and different length-diameter ratios of steel fiber were made,and the tests of cube compressive strength,splitting tensile strength and flexural strength were carried out.The mechanical properties of copper coated steel fiber concrete were obtained,which provided the date support for subsequent numerical simulation.At the same time,the influence of volume content and length-diameter ratio of steel fiber on the mechanical properties of SFRC was discussed,and the empirical formulas for predicting the compressive strength,splitting tensile strength and flexural strength of SFRC were proposed.(2)The digital image correlation(DIC)technology was used to synchronously observe the full-field strain of the cube compressive strength test and the flexural strength test to obtain the changes of strain field and displacement field on the specimen surface throughout the entire process of the test.On this basis,the development of cracks on the surface of the specimen and the failure form of the specimen were studied,the variation law of opening displacement and extension length of cracks in flexural test was revealed.(3)A method for establishing the two-phase meso-finite element model of SFRC was proposed.Firstly,the concrete matrix was established with solid elements,and the spatially randomly distributed steel fiber truss elements were generated by a Python Script in ABAQUS,and then the steel fiber were embedded in the concrete matrix by embedding element method to establish the two-phase meso-finite element model of SFRC.Secondly,the reasonable material constitutive(the bilinear elasto-plastic constitutive for steel fiber and plastic damage constitutive for concrete)was selected to describe the deformation behavior of each phase.The modeling method laid a foundation for the numerical simulation of SFRC.(4)Based on the above modeling method,ABAQUS was used to simulate the compressive,splitting tensile and flexural tests of SFRC respectively,and the predictive ability of the model was verified based on the test results.The basic mechanical property response curves,stress contour plot,deformation contour plot and damage contour plot obtained by simulation were in good agreement with the experimental results,verifying the accuracy of the numerical simulation method.Furthermore,the numerical model was used for parametric analysis to discuss the effects of factors such as steel fiber volume fraction,length,and diameter on the basic mechanical properties of SFRC.