Experimental and numerical investigation behavior of axial loaded reinforced concrete columns under high temperature

Although reinforced concrete structures are traditionally designed to carry service loads and lateral forces caused by seismic events, it is clear that the high-temperature caused by events such as fire should be also taken into account as hazardous phenomena that can significantly affect the safety of these structures. High-temperature exposure can considerably reduced the structural performance and load carrying capacity of reinforced concrete members, and therefore lead to a partial or total collapse. To address this issue, this study aims to investigate the axial load bearing capacity of reinforced concrete columns exposed to high temperature. In the study, a special electric furnace and cooling system which can apply ISO 834 standard fire curve automatically by computer control system is used to give reinforced concrete column elements with high-temperature effect under constant axial load. When the expected temperature value and heating time were reached, the axial load carrying capacity of the column was determined by increasing the load which was kept constant after the water-cooling or self-cooling application according to the experimental scenario. The main parameters of the study were concrete strength, heating time and cooling type. Thus, the change in stiffness and bearing capacity of the column specimens after high temperature was investigated. Reinforced concrete column specimens were also numerically modeled and analyzed using the Abaqus program to verify the experimental results. According to the experimental studies, the decrease in axial load carrying capacity increased as the heating time increased, the self-cooling capacity of the specimens applied to 120 minutes of high temperature decreased by 9.5%, while this ratio was determined as 35% in the water-cooled column. This has shown that the capacity decrease due to thermal shock, especially in vertical bearing elements, should be taken into account during the water intervention of the building exposed to fire.