Experimental investigating the loading capacity of steel cross-shaped columns with lateral links and partially encased composite columns under the fire load

In recent years, high-rise constructions and the possibility of fire incidents have posed a challenge for engineers and individuals working in this field. Due to the lack of research on fire safety, the current study aims to explore the performance of steel cross-shaped columns and partially-encased composite columns under fire conditions. To investigate the behavior of these columns, four groups were built on a laboratory-scale with variations in applied temperatures and concrete reinforcement. The first group consisted of steel cross-shaped columns with lateral links, as well as partially-encased composite columns at ambient temperature. Subsequent groups were exposed to temperatures of 300 °C, 600 °C, and 800 °C, respectively. Each group of columns underwent simultaneous axial loading and fire exposure. The research focused on the impact of lateral links, temperature increases, and the presence of concrete as a fire-resistant layer. Results indicated that the presence of lateral links altered the failure mechanism. Additionally, the presence of concrete at ambient temperature not only increased stiffness but also enhanced the load-bearing capacity by 36% compared to similar steel columns. Furthermore, the steel columns experienced a decrease in axial load-bearing capacity by 34, 29, and 10% at 800 °C compared to temperatures of 25,300 and 600 °C, respectively. In addition, it was found that if occurrence of the first deformation due to fire exposure is set as the failure criterion at 800 °C, the loss of load-bearing capacity will be 40% compared to the ambient temperature.