This differ from the Strength limit states because the event for which the bridge and its components are designed has a greater return period than the 75-year design life.

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

Answer: (A)

Extreme-Event limit states focus on rare, high-magnitude events whose return period exceeds the structure’s design life. Since the event the bridge must withstand has a return period longer than the 75-year design life, this framework is used rather than the Strength limit states. Strength limit states protect against collapse under loads that are expected within the design life, while they don’t specifically address extremely rare events. Fatigue and Fracture limit states deal with damage from repeated loading and crack growth, not a single rare event, and Service I concerns serviceability like deflection and crack width, not extreme incidents. So the scenario aligns with Extreme-Event limit states.