A dolphin is a group of

piling A deep foundation is a type of foundation that transfers building loads to the earth farther down from the surface than a shallow foundation does to a subsurface layer or a range of depths. A pile or piling is a vertical structural elemen ...

s 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 A mooring is any permanent structure to which a vessel may be secured. Examples include quays, wharfs, jetties, piers, anchor buoys, and mooring buoys. A ship is secured to a mooring to forestall free movement of the ship on the water. An ''an ...

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. Typical uses include extending a berth (a berthing dolphin) or providing a mooring point (a mooring dolphin).

To protect structures

Dolphins are also used to protect structures from possible impact by ships, in a similar fashion to boating fenders. A notable example of dolphins used to protect a bridge is the

Sunshine Skyway Bridge The Bob Graham Sunshine Skyway Bridge, often referred to as the Sunshine Skyway Bridge or the Sunshine Skyway, consists of a pair of long beam bridges with a central cable-stayed bridge that spans Lower Tampa Bay to connect St. Petersburg, ...

across the mouth of

Tampa Bay Tampa Bay is a large natural harbor and shallow estuary connected to the Gulf of Mexico on the west-central coast of Florida, comprising Hillsborough Bay, McKay Bay, Old Tampa Bay, Middle Tampa Bay, and Lower Tampa Bay. The largest freshwater ...

. In 1980, the

MV Summit Venture The MV ''Summit Venture'' was a bulk carrier that is best known for colliding into the Sunshine Skyway Bridge in 1980. It was built in 1976 by Oshima Shipbuilding Co. of Nagasaki, Japan. She was long, had a breadth of , deadweight of 33,912 tons, ...

hit a pier on one of the bridge's two, two-lane spans causing a 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 1/4 mi (1/2 km) to either side of the main span. The cost of the dolphins was $41 million (approximately $90 million in 2017 dollars).

To support navigational aids

Dolphins are also used to house navigation aids such as lights or daybeacons, and display regulatory information such as speed limits and other safety information, or advertising.

References

{{DEFAULTSORT:Dolphin (Structure) Nonbuilding structures Nautical terminology

Structure

Use

As mooring point

To protect structures

To support navigational aids

See also

References