Steel structural members ________ (________) when heated which tends to push the walls out.

• A. Warp
• B. Lengthen (elongate)
• C. Shorten (shrink)
• D. Twist (torsion)

Answer: (B)

When steel is heated, it expands along its length. This happens because the material has a coefficient of thermal expansion: as temperature rises, the atomic spacing increases, causing the length to grow. So the correct idea is that it lengthens or elongates.

This expansion can push connected walls outward if the steel member is restrained or connected to the walls, especially in long structural members. The amount of expansion is proportional to the original length and the temperature rise (delta L ≈ alpha × L × delta T), so longer members or larger temperature increases produce more noticeable movement.

Warping or twisting would require nonuniform heating or external bending moments, and shortening occurs when cooling.