What hazard is commonly associated with open-web steel joists in a fire?

• A. They can fail and contribute to structural collapse
• B. They become noncombustible and strengthen the structure
• C. They have no impact on fire behavior
• D. They restrict water flow in the system

Answer: (A)

Open-web steel joists are made of steel that loses strength rapidly when exposed to heat. The slender web members and connections in these joists are especially vulnerable to heat-induced buckling and bearing loss. As the joists weaken, they sag, distort, or fail, removing support for the floor above. Once the joists fail, the floor can collapse or partially fail, which in turn can drive a progressive collapse and compromise fire barriers between levels. So the major hazard is that they can fail and contribute to structural collapse.

They don’t become noncombustible or strengthen the structure in a fire, and they do have an impact on fire behavior through heat transfer and load-path changes, not by restricting water flow.