Abstract
The purpose of this paper is to make the influence of spiral reinforcement clear on the fire endurance of CFT columns without fire protection experimentally and to formulate relations between the load bearing capacity and heating time. The following findings were obtained from the test results. 1) Relations between the quantity of spiral reinforcement, axial force and fire resistance time were cleared, and the formula considering the spiral reinforcement for load bearing during fire was made. 2) When axial force ratio is under 0.5, the lower the axial force ratio is, the better fire endurance of CFT columns with spiral reinforcement is. When axial force ratio is over 0.6, spiral reinforcement has no effects on fire endurance. 3) When axial force ratio is 0.3-0.5, CFT columns with spiral reinforcement maintain load bearing capacity under fire for over three hours without fire protection.
