Numerical Simulation And Calculation Of Bond Performance Between Deformed Bar And Concrete

The bond performance between reinforcement and concrete is an important part of reinforced concrete structure.The cracking,crack width,deflection,strength and ductility of structure are directly or indirectly related to its bond performance.In this paper,a suitable bond-slip constitutive relation is selected by comparison.The constitutive relation is a continuous derivative function,which takes into account the influence of concrete strength,cover thickness,reinforcement diameter and other parameters.The existing test data are used to verify the correctness of the constitutive relation.Then,by using the constitutive relation and the basic stress equation and boundary conditions of the anchorage bar embedded in the concrete,the numerical recursive iterative method is used to solve the stress,slip and bond stress responses of reinforcent along the anchorage length direction,and the stress and slip at the load end of the reinforcement as well as the stress and slip distribution of the reinforcement can be obtained,the overall force-slip response of the component is obtained.The calculated results are compared and analyzed with the experimental results,and the comparison results are in good agreement with the experimental results.In order to obtain the stress state of the concrete and the failure mode of the component when the deformed steel bar is stressed,and avoid the influence of the bond slip constitutive relationship,this paper uses the solid finite element software to establish the three-dimensional model of the deformed steel bar by the method of equivalent relative rib area,and uses the circular rib with trapezoidal cross section to replace the crescent rib of the deformed steel bar.Different from the traditional twodimensional steel beam element model,this model reflects the rib part of the deformed steel bar,and only defines the normal hard contact and friction contact on the interface between the steel bar and concrete.In the steel bar pull-out experiment,the extrusion effect of the transverse rib of the steel bar on the concrete is reflected,which can more effectively simulate the interaction between the deformed steel bar and concrete.In this paper,the mechanism of specimen sliding and splitting in the process of drawing is further analyzed.By comparing the stress distribution of reinforcement and the bond stress distribution of the two calculation methods,the phenomenon of reinforcement stress penetrating inward when the concrete at the loading end is damaged is explained.According to the two numerical calculation methods used in this paper,the numerical simulation work of the steel bar drawing experiment is carried out,and the simulation results are compared with the existing test results to verify the validity of the simulation method and the model.The influence of the failure shape of the pullout specimen is compared and analyzed using the results of one-dimensional numerical calculation methods with Chinese standards and other national standards for calculating anchorage length.