Construction methods · Piers, pylons and abutments

Pier protection: fenders, dolphins and collision walls

A pier in a navigation route or beside a railway is protected from what can hit it: rubber fenders and floating fenders absorb ship energy, independent dolphins and artificial islands stop the ship before the pier, and a crash wall shields rail-side piers from derailed trains.

How bridges get built · Piers, pylons and abutments · Pier protection: fenders, dolphins and collision walls

Also called: ship impact protection, fender system, dolphin, crash wall

Pier protection: fenders, dolphins and collision walls — concept diagram — Concept diagram (TheBridgeEng)

How it is done

Estimate the design vessel and its energy (AASHTO or Eurocode 1-7); decide whether the pier resists the impact or a protection system absorbs it.
Install dolphins (pile clusters or caisson cells) upstream and downstream, or floating fenders on piles around the pier, or an island of rock fill.
For railways, cast a collision wall at least 2 m high and 0.75 m thick, or set piers back the required distance.

Where it fits

Navigable rivers and channels, sea bridges near shipping lanes, piers within 4.5 m of a rail track.

Where it does not

Relying on pier strength alone against large vessels; the energy is enormous.

Plant, pace and money

PlantPiling barges, rock placement, fender installation crews.

ProductivityWeeks per pier.

CostUSD 1-20 million per protected pier depending on the vessel.

Risks and controls

What goes wrong

Under-estimating vessel size growth over the bridge life; scour around islands.

Quality assurance

Energy calculation reviewed, fender performance certificates, inspection after any contact.

Examples

Sunshine Skyway (rebuilt with dolphins after 1980), Francis Scott Key collapse in 2024 renewed attention; the game marks piers in the navigation route as unacceptable.