dolphin (structure)
{{short description|Man-made marine structure}}
{{Use mdy dates|date=July 2023}}
File:Dalben aus Holz Suederelbe.jpgs grouped into a pair of dolphins serving as a protected entryway to a boat basin]]
A dolphin is a group of pilings arrayed together to serve variously as a protective hardpoint along a dock, in a waterway, or along a shore; as a means or point of stabilization of a dock, bridge, or similar structure; as a mooring point; and as a base for navigational aids.
Structure
Dolphins typically consist of a number of piles driven into the seabed or riverbed, and connected above the water level to provide a platform or fixing point. The piles can be untreated or pressure-treated timber piles, or steel or reinforced concrete piles. Smaller dolphins can have the piles drawn together with wire rope, but larger dolphins are typically fixed using a reinforced concrete capping or a structural steel frame.
Access to a dolphin may be via a pedestrian bridge, particularly in the case of mooring dolphins, but is often by boat.
Use
=As mooring point=
Dolphins are usually installed to provide a fixed structure when it would be impractical to extend the shore to provide a dry-access facility, for example, when the number of ships is greater than can be accommodated by the length of the berth/pier.{{cite book|last=Tsinker|first=Gregory P.|title=Port engineering: planning, construction, maintenance, and security |date=February 16, 2004|publisher=John Wiley & Sons|pages=474|isbn=9780471412748|url=https://books.google.com/books?id=kXaAKdwyJzYC&q=%22mooring+dolphins+are%22&pg=PA474}} Typical uses include extending a berth (a berthing dolphin) or providing a mooring point (a mooring dolphin).
=To protect structures=
File:Skyway Bridge old and new.jpg from ship collisions.]]
Dolphins are also used to protect structures from possible impact by ships, in a similar fashion to fenders.{{cite news|title= Robert Cabral, Plaintiff-appellant, v. Healy Tibbits Builders, Inc., Defendant-appellee United States Court of Appeals, Ninth Circuit. - 128 F.3d 1289|url=http://cases.justia.com/us-court-of-appeals/F3/128/1289/525073/|accessdate=November 30, 2010|date=October 15, 1997}} A notable example of dolphins used to protect a bridge is the Sunshine Skyway Bridge across the mouth of Tampa Bay. In 1980, the MV Summit Venture hit a pier on one of the bridge's two spans causing a {{convert|1200|ft|adj=on}} section of the bridge to fall into the water, resulting in 35 deaths. When a replacement span was designed, a top priority was to prevent ships from colliding with the new bridge. The new bridge is protected by 36 dolphins: four large dolphins protecting the two main pylons supporting the cable-stayed main span plus 32 smaller dolphins protecting bridge piers for {{convert|1/4|mi|m}} to either side of the main span.{{cite news|last1=Scherberger|first1=Tom|title=The Lesson - A Bridge On Guard Span's Protective Shield Called Best In The World|url=https://www.orlandosentinel.com/1987/03/22/the-lesson-a-bridge-on-guard-spans-protective-shield-called-best-in-the-world/|access-date=April 29, 2018|work=The Orlando Sentinel|date=March 22, 1987}} The cost of the dolphins was $41 million (equivalent to ${{Inflation|US-GDP|41|1987|fmt=c|r=0}} million in {{Inflation-year|US-GDP}} dollars).
See also
{{commons category|Dolphins (structure)|Dolphin (structure)}}
- Starling (structure) - a protective base for bridge piers