Numerical Study On The Stiffness Of Corroded Beam Based On The Cohesive Model

Durability of concrete structures is one of the most important issues in engineering and well bonding between concrete and steel bars is an important basis for ensuring the co-operation.Because of the great influence to the adhesion performance,the corrosion of steel bars has become one of the main factors affecting the durability of concrete structures.Because of the complex mechanism of transmission and many influencing factors of the rust interface layer,it is of great theoretical and practical significance to study the effect of the bond between concrete and corroded steel bars on the flexural rigidity of the beam and accurately evaluate the durability of the existing structure.The bond strength test of corroded reinforced concrete was introduced,and the test results of the non-corroded test piece and the rusted test piece were analyzed.Based on the experimental data,the calculation model of the bond-slip constitutive relation of the mutually independent multi-parameter corroded reinforced concrete considering the anchorage length l,the tensile strength ft of concrete,the thickness c/d of the protective layer and the thickness t of the corrosion product is given.The model is compared with the current influencing factors of empirical model.It is found that the reinforced concrete model is more reasonableBased on the experimental results and the cohesion model of the corrosion properties of the corrosion members,a bilinear cohesive force cell with thickness is established.Three-dimensional separation model of bearing capacity of reinforced concrete members with different degree of corrosion was established by introducing the interface layer.The stress and strain distribution of the concrete,the axial stress and the displacement distribution of the adhesive layer and the curve between the bearing capacity of the reinforced concrete beam and the mid span deflection are given and compared with the experimental results.it is shown that the bilinear cohesive force cell can effectively simulate the bonding mechanism between the reinforced concrete and the steel bars,and the bonding element with thickness determined by the depth of corrosion can reasonably describe the effect of the degree of corrosion on the bonding performance.The effect of the degradation of the bond between the concrete and the corroded steel on the flexural rigidity of the reinforced concrete beam is studied and the effect of the initial defects of the beam cross section on the flexural rigidity of the reinforced concrete beam is considered.Based on the stiffness analysis method,the calculation model of flexural rigidity of the corroded reinforced concrete beam with the effective height reduction coefficient γ,the steel strained uncoordinated coefficient m and the modified strain bar strain heterogeneity coefficient ’? is modified.Comparing the model with the experimental value and empirical value,it is found that the theoretical formula of bending stiffness correction of reinforced concrete beams is more accurate and realistic.The revised formula has been included in the relevant provisions of the revised national standards for durability evaluation of concrete structures.