Experimental Study Of Bearing Capacity On Damaged Cfst Short Columns Reinforced By Circular Steel Pipe Under Axial Compression

Experimental study of damaged CFST short columns strengthened by circular outerwear steel pipe refers to put the steel tube out of damaged CFST short column. And be filled with concrete between the inner and outer steel tube to form a new structure. The damaged concrete filled steel tubular specimens after reinforcement have good mechanical properties which bearing capacity is improved greatly.At present, the study of reinforced concrete column is more and reinforcement method is relatively mature. But for the reinforcement of concrete filled steel tubular column study is less and the method is relatively single mainly concentrated in through the outer wrapped CFRP reinforcement. When the outer steel pipe of concrete filled steel tube was damaged and the load transfer path changes, to find a reasonable method of reinforcement is very necessary. Consulting the method of previous studies; I put forward a method that reinforcing the damaged CFST short columns by coat steel. The specific research from the following several aspects.(1) Experimental specimens were designed 13 groups, including a group of the contrast specimen, three groups of specimens for damage and the other nine groups for reinforced specimens. Inner steel pipe damage rate is 5.05%,8.3% and 12.4% three levels and outer pipe wall thickness is 2mm,3mm and 4mm three levels. For axial compression experiment of the above specimens, observe the damage form of specimens, the analysis of load-displacement curve of the specimens and the internal and external steel tube of the load and strain curve.(2) Based on test data respectively drawing the relation curve of increasing coefficient SI of axial compression bearing capacity of coat steel reinforced CFST short columns with inner steel ferrule coefficient ξi and outer steel ferrule coefficients ξa. And the relation curve of ductility factor DI with ξi and ξa. The results show:The ductility of the member by the dual effects of steel tube and the outer steel tube. The ductility coefficient of reinforced specimens at about 2.43～3.22.Specimen C-IA- 04 ductility is best. After reinforcement, increase coefficient of bearing capacity of the specimen is between 2.63 and 3.62.(3) Multiple linear regression analysis was carried out on the test data. The relational model confining factor of specimens and increase coefficient of core concrete strength were worked out. At the same time deduced the calculation expression of ultimate bearing capacity of the damaged CFST short columns strengthened by outer steel pipe under axial compression. Based on limit equilibrium theory, combined with MATLAB, 1stOpt software to analysis stress state of steel tube and core concrete, deduced the calculation expression of ultimate bearing capacity of the damaged CFST short columns strengthened by outer steel pipe.(4) In order to analysis obviously of the mechanical performance of the specimens, using ABAUQS finite element software to simulate all specimens, include the deformation, stress and strain in the process of stress state, the ultimate bearing capacity analysis and simulation results are in good agreement with those obtained with the test results.