Impact behavior of concrete-filled steel tubular stub columns under ISO-834 standard fire

Drop weight setup was employed to experimentally study the behavior of concrete-filled steel tube (CFT) subjected to ISO-834 standard fire. The influences of fire duration time, impact velocity, impact energy and steel ratio on the impact resistance of CFT exposed to fire were discussed. The temperature histories of steel tube surface were measured and the force and compressive deformation histories of the specimens were recorded. The test results showed that fire duration time, impact velocity, impact energy and steel ratio significantly affected the impact behavior of CFT columns under fire, with the fire duration time being the most sensitive. However, the influence of other parameters on the ultimate impact strengths of the hot CFT columns was not significant. The residual deformations increased with the increase of fire duration time and impact energy, but decreased with the increase of steel ratio. Although the CFT specimens at room temperature or under fire suffered remarkable compressive deformations, the composite columns still remained good integrity. The test results showed that CFT under fire has an excellent impact resistance, thus is suitable to resist impact loads and collapse-induced dynamic loads.