Define a fracture-critical bridge.

• A. A bridge that is designed to carry loads beyond its rated capacity.
• B. A bridge with redundant load paths so that one component failure won't cause collapse.
• C. A bridge in which a failure of a single critical member or connection could cause collapse due to a lack of redundancy in the load path.
• D. A bridge where a failure of any single load-carrying member will not affect overall safety.

Answer: (C)

Fracture-critical describes a bridge where a single load-carrying member or connection, if it fractures, could cause collapse because there is no alternative path to carry the load. In such bridges, there isn’t redundancy in the load path, so the failure of that one member directly threatens overall stability. That’s why cracks or fatigue in those critical members demand close inspection and monitoring.

If a bridge has redundant load paths, meaning other members can take on the load if one member fails, it is not fracture-critical—the collapse isn’t imminent from a single fracture. The idea behind fracture-critical is exactly the lack of that backup path.