Experimental And Theoretic Study On Compression Characteristics Of Composite Column With Core Of High-strength Concrete Filled Steel Tube

With the development of the high-rise building in our country, steel reinforced concrete (SRC) are researched and implemented comprehensively. As a kind of SRC, the high-strength concrete filled steel tube reinforced concrete (CFSTRC), which shows an alluring applying prospect, is endowed with better mechanical property than the common SRC structure, due to the confined concrete by steel tube. However, due to the little systematical research on the CFSTRC, and it is not convenient for design, application.The mechanics performance under pressure is experimentally studied, with 10 high-strength concreted composite column filled steel tubes with different section, a steel tube concreted composite column and a RC column. The nonlinear finite element method (FEM) analysis results are also obtained.Firstly, the experimental study on the axial press composite stiffness of 12 test units, in the range of elasticity, is conducted to observe the influence of sector factors such as the position coefficient, stirrup ratio, steel tube ratio and the core concreted expand additive quantity. According to the widely study on many literatures and regulations, The appropriate methodology to calculate the axial press composite stiffness is developed, which separates the CFSTRC into the outer steel concrete, which is out of steel tube, and the steel tube with high-strength concrete filled, and calculates their axial press composite stiffness respectively to compose the whole stiffness of column, which are compared with the experimental results.Then, the failure mechanism analysis is conducted with small eccentricity pressing test of 10 test units, which indicates that there exists a total yield point in the small eccentricity pressing of the CFSTRC test units. Around the total yield point, the turn of the longitudinal strain is found, and the similar phenomenon is also indicated in the nonlinear FEM analysis. The influence on the mechanical characteristics under small eccentricity test, caused by the position coefficient, stirrup ratio and steel tube ratio, is also experimentally studied in this paper.Finally, the nonlinear FEM analysis is introduced for theoretical study. With the FEM model built in this paper, the mechanical characteristics of 8 CFSTRC test units, under the axial and small eccentricity press, is studied in details.