From a fire service viewpoint, which of the following is another weakness of steel?

From a fire service viewpoint, which of the following is another weakness of steel?

• A. It becomes harder when heated
• B. It expands minimally when heated
• C. It resists deformation at high temperatures
• D. It softens and elongates when heated

Answer: (C)

In a fire, steel loses strength as temperature rises, becoming softer and more deformable. When exposed to high heat, its yield and ultimate strengths drop and its stiffness decreases, so a member under load can bend, sag, or elongate before it fails. That makes the tendency to soften and elongate when heated the key weakness from a fire service perspective. It doesn’t harden with heat, and it doesn’t resist deformation at high temperatures; in fact, it expands and deforms more readily under fire conditions.

In a fire, steel loses strength as temperature rises, becoming softer and more deformable. When exposed to high heat, its yield and ultimate strengths drop and its stiffness decreases, so a member under load can bend, sag, or elongate before it fails. That makes the tendency to soften and elongate when heated the key weakness from a fire service perspective. It doesn’t harden with heat, and it doesn’t resist deformation at high temperatures; in fact, it expands and deforms more readily under fire conditions.