| Reinforced concrete(RC)column might be due to poor quality of construction or concrete aging in practical engineering,leading to the partial strength of the RC column be deteriorated and the safety and durability of building structures be affected.For these cases,the overall confinement will cause the waste of resources.Few literatures are involved in partial confinement only to the defect parts.Due to the excellent mechanical properties,the steel tube can provide a good constraint,and the construction is simple and fast.So it has been paid more and more attention in the field of structural strengthening.At present,researches on the bearing capacity of steel tube strengthening RC column at home and abroad are not enough.The experimental research on the simulation of the local defect section in RC column strengthened with steel tube is very few,and the proposed design methods are not satisfactory.In this paper a practical method based on the concept of steel tube confined concrete for strengthening the bearing capacity of RC columns has been presented.In this method,the gaps between the steel tube and the concrete of the original column are filled by the pressure grouting technique.In the case of not changing the column section,the restraint effect of the steel tube is brought into play and the maximum extent is involved in the overall force of the structure.In this paper,the experimental study and ABAQUS finite element simulation of strengthening the weak section of the frame column with the square steel tube were conducted.The performances of the RC column with local weak sections confined by square steel tube under axial compression were analyzed.And the feasibility and effectiveness of using this method to strengthen the RC column is verified.The factors affecting the strengthening effect were discussed to provide references for the popularization and application of this method.The content of this thesis consists of:(1)Finite element analysis: Using ABAQUS finite element software,the numerical simulations of axial compression of 14 specimens were carried out.And the factors such as the thickness of the steel tube,the strength of the weak area,the length of the strengthening section and the strength of the steel tube were studied to analyze the influences of the steel tube strengthening the axial compression bearing capacity of local weak sections in RC columns.At the same time,the stress distribution and development of each component in the process of the strengthened column were analyzed,and the working mechanisms of RC columns strengthened by square steel tube under complex loads were further revealed.(2)Experimental study: 3 square section short columns with local weak strength area were made.These columns were strengthened by the practical method proposed in this paper with 3 kinds of thickness square steel tubes.And the effects of the method were verified by measuring the load value,the axial displacement and the strain of the steel tube.The influences of the thickness of steel tubes on the axial compression performance and the basic stress law were analyzed.(3)Conclusions: According to the computer simulation and experimental results analysis,without changing the original RC column section size,the practical method proposed in this paper can significantly improve the bearing capacity and improve the ductility and mechanical properties of RC columns.Finite element software analysis and experimental results are shown that the thickness of square steel tube is an important factor to determine the bearing capacity of RC column.When strengthening the RC column through steel tube confined method,selection of steel tube thickness should be reasonable to give full play to the confinement effects to achieve the anticipated strengthening effect and make full use of material properties.(4)Finally,through the analysis of the existing achievements and shortcomings of this paper,some suggestions were given for the future research direction of the steel tube restraint practical strengthening technology.This paper innovation points are the following points:(1)A practical technique for strengthening the compression capacity of RC columns based on the concept of steel tube confined concrete were proposed.This technology was developed by this research team and has been applied in practical engineerings.(2)The experimental specimens simulated the actual RC column containing the weak strength area in practical engineerings,which makes the whole experimental research more close to the real strengthening engineerings.(3)For the first time,the steel tube confined strengthening technique were used to strengthen the partial section of RC columns.The actual effects,the influencing factors and the basic stress mechanism of the axial compression capacity of the strengthened specimens strengthening were studied... |
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