Behaviour of Concrete-Filled Steel Box Columns in Fire

• Main Authors: Lin, Jheng-Yi, 林政億
• Other Authors: Chen, Cheng-Chih
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/63672561596101088565

博士 === 國立交通大學 === 土木工程系所 === 104 === This study was conducted experimentally and numerically to explore the fire resistance of axial-loaded concrete-filled steel box columns exposed to fire. According to the test results, a fire resistance formula was proposed. Four specimens were designed and tested to study the temperature distribution on cross section, the axial deformation, and the failure mode, and to investigate the effects of load ratio (30% and 60% of the ultimate strength) and shear stud on fire resistance. Finite element analyses were performed for both heat transfer and nonlinear static analyses and used to simulate the fire behavior of the specimens, and further to explore the individual deformation and the load-carrying capacity of the steel box column and the concrete. The fire resistance formula was established by means of least squares regression to fit lower bound of the test results of this study and literature. The test results showed that the specimens axially elongated due to the temperature increase when the specimens were exposed to temperature increase. Next, the specimens turned to shortening till failure. The failure mode was the compressive failure of the column, including shortening of the specimens, bulge of column steel plate, and crushing of concrete inside the steel box. Compared to the shear stud, the load ratio highly affected the axial deformation and the fire resistance. The analytical results indicated that the analysis reasonably predicted temperature distribution on the cross section and the tendency of the axial deformation of the specimens. The analysis results also revealed that the axial and lateral deformation of the specimens subjected to fire. Moreover, the individual load-carrying capacity during the fire duration of the steel box and the concrete could be calculated. Finally, a fire resistance formula was proposed to predict the fire resistance of the concrete-filled steel square box columns. The formula can conservatively and reasonably predict fire resistance and will benefit the performance-based fire resistance design.