A Rebar-UHPC Bond Model Based On Phase Field Theory And Damage Mechanics

Steel-reinforced concrete,as the most widely used composite in construction,exploits the full potential of the rebars and concrete via the bond between the two different materials.Nowadays,with the appearance of UHPC-a new concrete with ultra-high performance,the bond behavior between UHPC and its reinforcement incite a strong interest in research.Although the difference between UHPC and normal concrete in material properties has been thoroughly studied,the bond properties of rebar-UHPC still need deep analysis.Particularly,in experimental studies of bond behavior,when considering the independent variables,such as yield strength of reinforcement,diameter of reinforcement,anchorage length for bonding area and Compressive strength of UHPC,there is a deficiency of knowledge about the dominant ones affecting the bond-slip behavior.In addition,the mechanism of the bond strength and residual stress after sliding still lacks of deep analysis.In general,it is necessary to carry out a comprehensive study on the bond behavior of rebar-UHPC interface,especially in the current industry with progressive demanding for structural safety.To address the problems,this research investigated the experimental data collected in this decade about the bond behavior between rebars and UHPC,and tried to build a database which mainly contains the bond strength,residual stress and corresponding slides,according to different independent variables.In order to find the dominate factors in the variables,this research relies on machine learning and causal inference method to dig into the data,and finally find the rank of significance of each factor.To find the equations for the critical bond properties as functions of the dominate variables,the Scikit-Learn multi variable nonlinear regression method is employed.At the end,based on the damage mechanics and phase field method,a novel four-node zero-thickness cohesive element in the form of User-defined-element in FEM platform Abaqus is developed including the constitutive law obtained above.The efficiency and accuracy of the simulation using this element is verified by the experimental data,which means that this element is capable of representing the Bond behavior of rebar-UHPC interface.