Post-fire performance of structural steel

Abstract

Carbon steel is widely used in building industry. The different structural element might be exposed to high temperature during fire. The structural safety of steel buildings must be evaluated after they have suffered a fire. The assessment requires understanding the behaviour of carbon steel after heating. Therefore, this paper is aimed at studying the post-fire behaviour of carbon steel. A total of seventeen coupon specimens were tested by uniaxial tensile test. One of them was tested without heating and considered as a reference. Sixteen specimens were heated at a temperature of either 400°C or 700°C for different durations. Eight specimens were cooled in air and the others cooled in water. Heating durations were 30 min, 60 min, 90 min and 120 min. Results showed that the high-temperature has a great influence on decreasing the ultimate and yield stress and elongation for specimens cooled in the air. For specimens cooled in water, the decreased in yield and ultimate stress was minor comparing to the reference specimen. The ductility of water-cooled specimens showed a noticeable reduction comparing to specimens cooled in air. Increasing the heating time results in higher elongation for specimens heated to 400oC and lower elongation for specimens heated to 700oC, but the specimen loses strength in both cases.