Effect Of Steel Fiber On Splitting Tensile Fracture Resistance Of Concrete

The tensile property of concrete material is poor,easy to crack the structure,resulting in weak durability,so the main development direction of improving the life of reinforced concrete structure is to enhance the toughness and tensile cracking resistance of materials.Adding steel fiber into concrete can reduce the brittleness of concrete,prevent crack generation and delay crack cracking,which is of great significance in practice.Based on this,the crack development in steel fiber reinforced concrete is studied as follows and the conclusion is drawn:(1)The basic mechanical properties of the material were studied and analyzed by axial compression and Brazilian disc splitting tests.The load displacement curve during the loading process was obtained,and the mechanical parameters such as compressive strength,splitting strength and elastic modulus were obtained.It is found that compared with the increase of compressive strength,steel fiber with the same dosage can improve the tensile properties of concrete more obviously.(2)Through wedge splitting test,fracture parameters such as initiation load,failure load,fracture toughness and fracture energy were calculated.By observing the whole process development of fracture zone,it is found that steel fiber has an obstruction effect on crack propagation or extension,and the bearing capacity of steel fiber specimen decreases more gently after cracking.Electrical strain gauge and digital image correlation method(DIC)were used to monitor the whole process of specimen deformation.The changing curve of opening displacement with load and the distribution curve of opening displacement on the ligament under different loads were obtained by the electrical measurement method.Meanwhile,the strain field variation nephogram of the specimen was obtained by DIC,and the opening displacement was calculated,which was compared with the electrical measurement data of the strain gauge.It is found from the strain cloud map that when the steel fiber concrete wedge specimen breaks,there are short cracks outside the main crack,and the main crack is not coherent,which reflects the bridging effect of steel fiber.(3)The bearing capacity calculation formula is obtained from the double K fracture criterion of concrete,and it is found that the peak load data of the test is in good agreement with the peak load curve obtained from the calculation formula.Based on the cohesive crack model and damage factor calculation method,the theoretical opening displacement and damage factor are obtained.Combined with the experimental data,it is found that the measured values of the opening displacement are consistent with the trend of the model’s opening displacement curve,and the distribution law of the cohesive crack opening displacement and damage variables in the fracture process region is given.(4)Combined with the test data,the concrete wedge splitting model was established based on Abaqus and Python,and the numerical simulation of the whole process of crack propagation was completed.The load and opening displacement curves obtained by the simulation results are in good agreement with the test results,which verifies the accuracy of the test data.The crack image of the splitting model shows that the wedge specimen maintains type Ⅰ crack during tension,which is consistent with the test results.