Fire Performance of structural steel tubular sections with passive fire-resistant Mortar

Fire protection materials must limit the rise in temperature in steel components to prevent early steel deterioration and structural collapse in the event of a fire. Therefore, fire protection in steel structures must be efficient, optimised, and cost-effective to make them more competitive. The versatility of coldformed steel (CFS) products is currently being investigated through their extensive use in various structural applications. Cold-formed steel tubular sections of grade YSt-355 and sectional dimensions of 180x180x6 mm and 3 metres long are used to investigate the fire performance of sections with passive fire-resistant (PFR) mortar. For this purpose, three full-scale fire experiments were performed on CFS tubular columns exposed to a standard fire curve ISO-834. In addition, the experimental investigation of the mechanical properties of the structural steel at ambient and elevated temperatures was conducted. A commercially available low-cost passive fire-resistant mortar particularly used for the concrete structures in tunnel linings, was used to enhance the fire-resistant rating (FRR) of the CFS tubular section. One tubular column specimen as a control specimen was left uncoated (SS1-00CM), while the other two specimens were coated with 20 mm (SS2-20CM) and 40 mm (SS3-40CM) thick fire-resistant mortar coating over the Grip primer. The columns were then subjected to an axial compressive load of load factor 0.35 prior to the initiation of fire load. The FRR is remarkably increased by nine times with the use of PFR on CFS tubular sections, and a drastic decrease in the internal surface temperature was noticed during the detailed experimental investigation, making it the most economical and efficient PFR mortar.