| Concrete Filled Tubular (CFT) structures become more widely accepted and used in tall buildings as well as arch bridges, while recent researches demonstrate local plastic buckling may occur at the ends of the steel tube followed by the crushing of internal concrete, which may result in unstable hysteretic loading capacity, particularly for columns with higher axial load. Based on the concept of Confined Concrete Filled Tube (CCFT) conceived by Xiao, this study investigates the seismic behavior of CCFT columns under axial compression and lateral cyclic loads for the first time. The proposed column system is an innovative concrete filled steel tubular (CFT) column system for improved seismic design of steel and concrete composite structures. Based on fundamental mechanics, the design concept is aimed at controlling the local buckling of the steel tube and confining the concrete in the potential plastic hinge regions of a CFT column. To achieve this, several efficient details of transverse confinement were recommended and 7 specimens were examined through experimental research.1. A simple and reliable test set-up is designed to meet the demands of tests. 2 groups of specimen with the diameter-to-thickness ratios of 112 and 54, respectively, were constructed for test use.2. The action of main affected factors, such as details of additional transverse confinement, loading history, diameter-to-thickness ratios and so on, are described in details to investigate the seismic behavior and mechanism of columns under cyclic load.3. The thesis also proposes an analytical model capable of predicating the flexural and axial load strength of CCFT members for monotonic loading conditions.
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