Which statement best describes how structural steel behaves under fire and how stability is maintained?

• A. It gains strength when exposed to heat and requires no protection.
• B. It loses strength with heat and is protected by fireproofing coatings or enclosures to maintain stability.
• C. It becomes completely fireproof after a short exposure.
• D. Its strength increases with temperature but is unaffected by protection methods.

Answer: (B)

Structural steel loses strength and stiffness as it heats up, so its ability to carry loads deteriorates in a fire. Without protection, temperatures rise quickly and the steel can yield, deform, or fail under the building’s dead and live loads, compromising stability. To keep the structure stable for the required time, steel is protected with fireproofing coatings or enclosed within fire-rated assemblies. These protections slow heat transfer into the steel, helping to preserve its strength and delay collapse, which is why fire-resistance-rated coatings or enclosures are essential for maintaining stability during a fire.