Analysis Of Interfacial Mechanical Behavior Of Steel Fiber Cement Based Materials Based On CDP Model

The bond performance of the interface transition zone between cement matrix and steel fiber is an important content to study the mechanical behavior of steel fiber reinforced concrete.The pull-out test of a single steel fiber is an important research method for the bonding performance of the interfacial transition zone between cement matrix and steel fiber,but the test has some limitations,such as unable to reveal the stress-strain behavior between the interfaces.Based on the concrete plastic damage model(CDP model)and cohesion model(cohsieve model)of ABAQUS,this thesis uses the two-dimensional and three-dimensional finite element analysis method to analyze the process and mechanism of steel fiber pulling out,and explore the law of mechanical behavior of interface transition zone of steel fiber reinforced concrete.The main research contents and conclusions are as follows:(1)The steel fiber pullout test in the literature is studied by axisymmetric two-dimensional finite element method.The nonlinearity of cement matrix is simulated by CDP model,and the interfacial transition zone is simulated by cohsieve behavior.The effects of steel fiber embedding length,interfacial friction coefficient,end adhesion of steel fiber,steel fiber modulus,contact properties between materials,elastoplasticity between steel fiber and concrete,elastic modulus of interfacial transition zone,matrix strength and lateral load on the interfacial mechanical behavior of steel fiber cement-based materials are studied respectively.The results show that the axisymmetric two-dimensional model combined with CDP model and cohsieve behavior analysis can effectively simulate the load displacement curve of fiber and the stressstrain behavior between interfaces.However,the axisymmetric two-dimensional model has the problem that the simulation effect of the stage other than the peak load and sliding stage is poor.(2)Establish a quarter of three-dimensional solid model,simulate the cement matrix in the CDP model,consider the descent of coh3d8 element in the cohsieve element to solve the problem of poor simulation effect in the partial and complete debonding stage,and further explore the buried length of steel fiber,the values of friction coefficient and bonding coefficient,the elastic modulus of steel fiber,contact properties,material elastoplasticity,interface elastic modulus,matrix strength grade,lateral load and other factors,Effect on the interfacial mechanical behavior of steel fiber cement-based materials.The results show that the dynamic analysis can simulate the influence of debris in the cavity during the pulling out of steel fiber,and can better reflect the interfacial mechanical behavior of steel fiber cement-based materials under 3D conditions.The disadvantage is that the calculation cost of 3D model is high.(3)The combination of CDP model and cohsieve model can verify the value of the parameters of the transition zone between concrete and interface and the bonding performance between the research interface.The analysis shows that in the four stages of complete bonding,partial debonding,complete debonding and sliding of steel fiber pulling out in the numerical simulation,the contribution of friction is the largest and participates in the whole stage,the contribution of physical and chemical bonding is only in the final sliding stage,and the contribution of mechanical bite is only in the complete bonding stage.The bonding performance between interfaces is greatly affected by the factors such as fiber embedding length,friction coefficient,matrix strength and lateral load;The interfacial elastic modulus and end adhesion have little influence.In general,CDP model and cohsieve model can better simulate the interfacial mechanical behavior of steel fiber cement-based materials,and can solve the limitations of interfacial stressstrain behavior that can not be obtained in the test.2D analysis is more suitable for interface research,and 3D analysis is more suitable for studying the mechanical behavior between interfaces.The above research methods and the obtained interfacial mechanical behavior of steel fiber cement-based materials can provide reference for relevant research.