1. Dolphins are less expensive than designing piers for direct impact forces
2. Dolphins redirect vessels away from piers, preventing direct impacts
3. Pier design for vessel impact often conflicts with seismic design requirements
4. Dolphins allow for shared protection of multiple bridge piers with a single system

Explanation

Explanation: Dolphin protection systems are fender-like structures designed to redirect vessels away from bridge piers, preventing direct impacts altogether—a more effective strategy than designing piers themselves for massive collision forces (which AASHTO LRFD Section 3.14.15 can require to be several thousand kips). Dolphins absorb and deflect vessel energy through structural deformation or friction systems, protecting both the vessel and bridge. Cost considerations (A) vary widely by site and can favor either approach; seismic compatibility (C) is addressable in direct-design; and multiple-pier protection (D) is site-specific, not a universal advantage of dolphins.

Learning Resources:

• Review AASHTO LRFD Bridge Design Specifications, 9th Edition (2020), Section 3.14.15 for vessel collision load requirements.
• Study the Sunshine Skyway Bridge disaster (1980) and subsequent protection system design.
• Digital Resource: Access PIANC Guidelines for the Design of Fender Systems (https://www.pianc.org/publications)
• Tip: When designing vessel collision protection, consider both static and dynamic response characteristics, accounting for vessel mass, approach velocity, and impact angle.