Damage effect of steel circular tube subjected to fire and blast

Abstract

Q345B steel circular tubes are widely applied in structural engineering applications, such as offshore platforms, bridges, and other structures, and they face potential risks of being subjected to the external loads of fires, explosions, or both during their service lives. In this study, the damage of Q345B steel circular tubes due to the combined action of fire and blast loading were analyzed. A specialized experimental platform was built, and experiments were performed on Q345B steel tubes with a range of wall thicknesses (a), fire loading durations (t), and stand-off distances (R) which means the distance between the bottom of the explosive and the upper surface of tube. The experimental local deflection, compressed degree, and local deformation volume are presented and studied in a quantitative manner. As the fire duration increased, the specimens underwent more noticeable deformation and damage. The local deflection amounts of the specimens treated with fire increased by 20%–50% compared to that of the specimen not exposed to fire at R = 17 cm. When R = 12 cm, the local deflection increased by 20%–120%. In addition, based on the stress–strain curves, the effects of the blue brittleness of the Q345B steel materials on the anti-blast performances of the specimens were examined. Finally, scanning electron microscopy was employed to explore the rupturing mechanism under a microscope.