Which construction type consists of unprotected steel joists and I-beams that may fail under fire?

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Multiple Choice

Which construction type consists of unprotected steel joists and I-beams that may fail under fire?

Unprotected steel weakens quickly when exposed to heat. In this construction type, the structure is built with noncombustible materials, but the steel framing—joists and I-beams—often isn’t protected with fire-resistive coatings or enclosure. As fire heats the steel, its strength and stiffness drop, leading to sagging or sudden failure of the members and increasing the risk of collapse. That vulnerability is exactly what this construction type describes, making it the best answer. By contrast, fire-resistive Type I protects steel, Type III uses masonry exterior with a wood interior, and Type IV uses large timber members that resist fire differently.

Unprotected steel weakens quickly when exposed to heat. In this construction type, the structure is built with noncombustible materials, but the steel framing—joists and I-beams—often isn’t protected with fire-resistive coatings or enclosure. As fire heats the steel, its strength and stiffness drop, leading to sagging or sudden failure of the members and increasing the risk of collapse. That vulnerability is exactly what this construction type describes, making it the best answer. By contrast, fire-resistive Type I protects steel, Type III uses masonry exterior with a wood interior, and Type IV uses large timber members that resist fire differently.

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