Fine Numerical Modeling Study Of Bond Slip Between Reinforcement And Concrete

The good bond behavior between steel and concrete is the foundation for the two to worktogether and bear loads together.Under load,the bond behavior between reinforcement and concrete may degenerate or even break,which directly affects the bearing capacity and deformation characteristics of components and structures.Therefore,it is necessary to consider the influence of bond slip between reinforcement and concrete in the fine simulation analysis of reinforced concrete structure.Based on this,scholars have developed a variety of bond slip numerical models and applied them to the simulation analysis of reinforced concrete members or structures.The above researches are helpful to reveal the local failure mechanism caused by bond degradation and improve the numerical simulation accuracy of reinforced concrete structures.However,there are still two problems in the existing studies:(a)none of the existing models can take into account the influence of complex stress states around the reinforcement;(b)under cyclic loads,existing models are all derived from the drawing test,and the stress state of concrete in this test is inconsistent with the reality.It is well known that reinforced concrete structures may crack and partially crush under load.These local damages will change the stress state around the reinforcement and further affect the bond slip performance between reinforcement and concrete.It can be seen that the existing models ignore the influence of local stress state,which seriously restricts its application in the refinement simulation of reinforced concrete structures.In order to overcome the above problems,this paper mainly carries out the following work and draws the corresponding conclusions:(1)A numerical model of bond slip that can consider the influence of complex stress states is proposed.The planar four-node bond element with zero thickness is established,which can satisfy the unification of accuracy and efficiency of numerical analysis.Based on independent development combined with ABAQUS subroutine,the embedded numerical model is realized;By using this numerical model,concrete stresses at specified locations can be collected in real time,and the bond stiffness matrix of reinforcement-concrete can be updated in real time,so the influence of complex stress state on bond-slip behavior can be considered accurately.After a large number of numerical tests at element and component levels,the model can better reflect the prediction effect of the constitutive model,and has good numerical stability and convergence.(2)The bond-slip hysteretic model of reinforced concrete is proposed and the corresponding numerical model framework is established.The cyclic bond behavior deterioration of well-restrained concrete is studied by processing and analyzing the data of innovative and improved bending beam test.The effects of concrete compressive strength,steel bar size and slip history on bond strength were investigated.The main parameters of the bond-slip hysteretic model of reinforced concrete are checked by experimental data.The corresponding numerical model framework is mainly combined by user subroutine UEL and URDFIL of ABAQUS.The model Can reasonably judge the forward and backward loading and unloading status and record maximum slip and cumulative slip.Therefore,the bond degradation behavior of reinforced concrete is considered accurately.(3)The numerical model frame of bond-slip of reinforced concrete and the hysteretic model frame of bond-slip of reinforced concrete under complex stress state based on element hierarchy are applied to practical reinforced concrete columns.Based on the analysis of the variation law of the stress in the element layers,it is found that the variation law of the stress in the element is in accordance with the overall stress of the column,which proves the accuracy of the two numerical model frameworks.Moreover,the bond-slip behavior of reinforced concrete columns under different lateral forces can be simulated by the numerical model frameworks under complex stress conditions,while the bond-slip behavior of reinforced concrete columns can be simulated by the numerical model frameworks.The bond-slip hysteretic model frame can simulate the bond degradation behavior of reinforced concrete columns with different corrosion rates,which proves that both of them have good convergence,stability and compatibility.