Research On Reinforcement Of Concret- Filled Steel Tube With Disengaging Based On MPC Composite

The concrete-filled steel tubular structure has been widely used in curr ent bridge engineering and even became the mainstream structural form of arch bridges.However,the voiding defects caused by the construction quality,concrete shrinkage and creeping,etc.,restrict the performance of the concrete-filled steel tubular structure.Based on the current mainstream management ideas,this paper innovatively uses MPC composite material to carry out secondary grouting treatment of hollow steel tube concrete,and investigates the restoration of axial compression performance of conc rete filled steel tube with MPC composite reinforcement treatment.This paper mainly completed the following work:Based on the existing research,this paper introduces and analyzes the working mechanism of concrete-filled steel tube,and based on the limit equilibrium theory,perfects the theoretical derivation of the ultimate bearing capacity of hollow steel tube concrete,and has a deeper theoretical understanding of the void defect,from the limit.The degree of influence of the void on the axial compression performance of the concrete filled steel tube is analyzed.Secondly,according to the research needs,21 concrete-filled steel tubular short-column specimens with different voiding rate,steel-containing ratio and reinforcement condition were designed,and the basic properties test of steel,concrete and MPC composite materials were completed.After that,the research and selection of the measuring point arrangement,test plan and loading method of the axial compression test of the test piece were com pleted.According to the scientific test plan,the displacement and strain monitoring of 21 specimens were carried out,and the deformation modes of the outer steel tubes and the damage forms of the internal concrete and MPC composites were recorded under different test parameters.The analysis results show that the MPC composite has excellent reinforcement effect on the axial compression performance of CFST specimens with different void ratio and steel content.By summarizing the existing research and combining the trial calculation work,the appropriate steel,concrete constitutive relationship,contact relationship between the materials were selected,and the actual test results of the MPC composite materials were combined to establish the 21 test pieces.The finite element model is solved by nonlinear finite element method of loading process using ABAQUS software.The calculation results are basically consistent with the test results,which play a mutual verification and complement each other.The finite element results were extracted,and the stress distribution,stress characteristics,bearing capacity variation and lateral deformation characteristics of the steel specimens were analyzed in detail.The final results show that the MPC composites can be effective.Improve the axial compression performance of the hollow-filled concrete filled steel tube,improve the stress distribution,restrain the degree of concave deformation of the steel pipe,and have good adaptability to the defect test pieces under different working conditions,and the reinforcement effect is stable,and the defect test pieces can be obtained.The ultimate bearing capacity is restored to more than 90% of the original test piece.Finally,the parameters of MPC composite reinforcement we re analyzed.The influence of different parameters on the reinforcement efficiency of different MPC types was calculated.The relevant laws were obtained and verified by experiments.