Which load combination is used to ensure long-term performance under repeated traffic loads and to evaluate fatigue?

• A. Fatigue and Fracture limit states
• B. Service II
• C. Extreme Event II
• D. Service I

Answer: (B)

The idea being tested is how engineers model the effect of many repeated traffic cycles on a bridge. Fatigue isn’t about a single large load; it’s about how countless cycles gradually degrade material strength over years. To capture this in design, a specific load combination is used that represents these repeated live-load effects over the structure’s life. This combination is designed to stress the member repeatedly without requiring the peak single-load event, so it can reveal potential fatigue damage and long‑term serviceability.

That’s why the option representing Service II is the best choice: it’s the load combination intended to account for long-term, repeated loading and to support fatigue evaluation. The other options address different conditions or limit states: a fatigue/fracture limit-state set describes what needs to be checked but isn’t itself a fatigue load pattern; an extreme-event combination targets rare, severe loads; and Service I covers normal service conditions without emphasizing the cumulative effect of repeated cycles.