Simulation Method For Bond Slip Of Section Steel-Recycled Aggregate Concrete Under Full Replacement Ratio

With the rapid development of construction industry,the alternation between new and old buildings is becoming more and more frequent.As a new type of green building materials,recycled aggregate concrete turns construction waste into treasure,which not only solves the problem of construction waste,but also alleviates the current situation of increasing shortage of construction raw materials.In the existing structures,Section steel concrete structure has the characteristics of large stiffness,high bearing capacity and good energy consumption,the RAC structure composed of RAC and section steel not only solves the problem of weak bearing capacity and seismic performance of RAC structure,but also has lighter dead weight and is more economical.Bond-slip performance is the prerequisite of collaborative work in composite structure,and due to the new-old mortar interface transition zone in the recycled aggregate surface and the internal microscopic cracks,the interface of RAC and internal crack development rate is differ from that of ordinary concrete,the bond-slip performance is also different from the section steel-concrete.Therefore,it is very necessary to study the bond slip performance between section steel and RAC,especially the section steel-recycled aggregate concrete under full replacement ratio,the interface is more complex and the utilization rate of recycled aggregate is the highest.Therefore,the research on the bond slip performance of RAC is the key to whether recycled aggregate can be applied to RAC components with full replacement ratio.In addition to the experimental study,section steel RAC bond-slip numerical simulation study is also the early stage of the important theoretical foundation of the project promotion and structure calculation,but this part of the research was lacking at present,especially for the most special section steel-RAC under full replacement ratio of bond-slip performance numerical simulation analysis is missing,so the research for the numerical simulation method is very critical.Based on previous research of team,the bond behavior degradation mechanism of section steel-full replacement ratio recycled aggregate concrete has carried on the experiment and simulation in this paper,which based on the control variable method that 9 specimens of section steel to explore four factors as the cover depth of section steel,the embedded length of section steel,the recycled aggregate concrete strength,the transvers stirrup ratio of bond behavior between section steel and recycled aggregate concrete.The following main conclusions are drawn through the experimental and simulation study of 9 pushed-bond slip specimens:1)The failure modes of the specimen are divided into two types: splitting failure and bursting failure.The initial crack of the splitting failure is located at the bottom of the loading end of the specimens.The initial crack of bursting failure is located in the middle of the specimen,and expands to both ends of the specimen until failure.The splitting failure is the typical failure mode.(2)the p-s curve of each specimen was analyzed and classified as two models according to its characteristic load characteristics,and it was found that the p-s curve was related to its failure mode;This paper analyzes and fits the relation of each factor to the characteristic bond strength,and three formulas are proposed for the bond stress between section steel and recycled aggregate concrete and fitting well.(3)The constitutive relation of characteristic bond strength can be expressed in the form of piecewise function,the rising stage can be expressed in the form of primary function,the falling and the residual stage can be expressed in the form of exponential function,and it is fitting well.(4)The advantages and disadvantages of three feasible plan for simulating bond strength in Abaqus were analyzed in the paper,and the nonlinear spring element was finally used to simulate bond strength.In this paper,the modified syntax of nonlinear spring element in “Inp” file is explained and detailed.Considering the influence of plastic damage of recycled concrete,a numerical simulation method of bond slip of regenerated concrete with steel-full replacement ratio has proposed in paper.(5)In this paper,nonlinear spring element in Abaqus was used to simulate the bonding strength which between section steel and recycled aggregate concrete.The simulation results showed that the normal stress gradually decreases from the loading end to the free end with embedded length of section steel.The distribution of the bond stress along the embedding length is relatively uniform.The distribution of bond stress of recycled aggregate concrete has analyzed and the improvement methods are proposed.