Box beam guardrails are constructed from what structural element?

• A. Rectangular steel beams
• B. Tubular rail system
• C. Cable railings
• D. W-beam

Answer: (A)

Box beam guardrails rely on a rectangular hollow cross-section, i.e., rectangular steel beams. The term “box beam” refers to a hollow rectangular section formed to create a box-like profile, which provides strong bending resistance and good torsional stiffness while keeping weight reasonable. This shape is chosen specifically for its ability to distribute impact loads along the guardrail efficiently.

Tubular rail systems use round tubes, which are a different cross-section and aren’t what a box beam is. Cable railings depend on wires rather than a solid/box cross-section. W-beam guardrails use a different, typically I- or W-shaped cross-section, not the rectangular hollow box shape. So the rectangular steel beam is the correct structural element for box beam guardrails.