Quays, Wharves, Jetties, Dolphins & Fenders Notes

Last reviewed 30 Sept 2026 · 9 min read

Berthing structures

A ship must be brought alongside a structure, held there safely, and loaded or unloaded. The main forms are:

Structure	Description
Quay	A solid structure parallel to the shore; ships berth along its face. Retains the fill behind it
Wharf	Similar to a quay; often used for open (piled) structures running along the shore
Jetty (pier)	A structure projecting into the water, generally on piles, with a deck above; ships berth alongside its head or its sides; open, so waves and currents pass through
Dolphin	An isolated structure (a cluster of piles or a caisson) standing in the water for berthing or mooring
Mole	A solid breakwater-like structure that also serves for berthing
Marginal wharf	A wharf built along the edge of the land

Quay walls (retaining structures)

A quay wall is a retaining wall with the sea on one side and the reclaimed land (fill) on the other. It resists the earth pressure, surcharge from cargo and cranes, water-level differences, and the berthing and mooring loads.

Gravity type

Block-work (masonry or concrete blocks): precast concrete blocks laid in courses on a levelled foundation; resistant and durable, but demanding for divers and the foundation must be strong.
Caisson quay: large hollow concrete boxes floated out, sunk on a prepared bed and filled with sand or concrete; fast to build; used in deep water.
Cellular (cofferdam) type: steel sheet-pile cells filled with sand or rock; the cells act as gravity walls.
Stability checks: sliding, overturning, bearing capacity of the base, overall (slip circle) stability of the soil below, and settlement. Water-level differences (from the tide) and hydrostatic pressure behind the wall require weep holes or a drainage filter.

Sheet-pile quay walls

Steel sheet piles (Z or U section) driven into the ground form a continuous wall, held near the top by an anchor (tie rod) and anchor wall or anchor piles; the anchor prevents the wall from rotating; the lower part is fixed in the soil by its embedment (a free earth support or fixed earth support design).
The ends of the tie rods are attached to a waling; the anchor is placed beyond the active failure wedge of the retained soil (the anchor must lie beyond the plane at $4 5^{\circ} + ϕ /2$ from the horizontal through the bottom of the wall).
Suited to moderate depths (up to about 12–15 m) and to soils where piles can be driven; economical and quick; needs corrosion protection.
Relieving platforms (a deck supported on piles behind the wall) reduce the earth pressure on the wall.

Diaphragm-wall and combined (king-pile) walls

Reinforced concrete diaphragm walls (cast in a trench) or combi-walls of large tubular piles with sheet-pile infill are used for deep berths (16–25 m) where large loads and cranes are carried; anchors or a relieving platform stabilise them.

Open piled jetties and wharves

The deck is supported on piles (steel, RCC, prestressed or timber); the sea passes through the structure, so it needs little reclamation, reduces wave reflection, and is economical in deep water.

Components: piles → pile caps or cross-beams → longitudinal beams → deck slab (precast or cast-in-situ); fender system, bollards, rail tracks for cranes; approach trestle connecting to the shore.
Piled wharf on a slope (open berth structure): the deck is supported at the crest of a dredged slope with rock protection; the slope carries the backup area.
Loads: dead and live loads (cargo, cranes, vehicles), berthing and mooring, wave, current and wind, earthquake, and thermal loads.
Design: the piles are designed as beam-columns, with lateral load through the soil (a soil-structure interaction analysis) and braced (raking piles) to resist horizontal forces.
Cargo: suitable for oil terminals, bulk loading berths, and general cargo berths.

Dolphins

A dolphin is a freestanding structure of piles or a caisson used to absorb the berthing impact or to hold mooring lines:

Breasting dolphins — take the ship's berthing impact and hold it against the wind and current; they carry fenders on the ship's side.
Mooring dolphins — provide bollards for the mooring lines only; positioned to give the best angle for the lines.
Connected to the jetty by catwalks for personnel access; used at oil and gas terminals, where the ship is moored to a jetty head, and at bulk terminals.

Fenders

A fender is a device placed between the ship and the berth to absorb the energy of the ship's berthing by deflecting, and to protect the ship and the structure from damage. Fenders convert the kinetic energy of the ship into the strain energy of the fender, and they limit the reaction force transmitted to the structure.

Type	Action
Timber fenders	Old system — timber piles and rubbing strips; low capacity
Rubber fenders — cylindrical, cone, cell, arch (V-type) and pneumatic (Yokohama)	The most common; rubber compresses elastically. Pneumatic fenders are air-filled floating cylinders
Foam-filled fenders	Closed-cell foam core with a tough skin
Gravity or spring fenders	Steel springs and counterweights
Hydraulic fenders	Oil-filled dashpots

The performance curve of a fender (reaction force vs deflection) is given by the manufacturer; the energy absorbed is the area under the curve. The design uses the rated energy absorption (E), with the reaction $R$ and the deflection $δ$ , including allowance for angle, temperature and velocity factors.

Berthing energy

The kinetic energy of a berthing ship to be absorbed by the fenders:

E = \frac{1}{2} C_{m} M V^{2} C_{e} C_{s} C_{c}

where:

$M$ = displacement of the ship (tonnes) → energy in kNm when $V$ in m/s and $M$ in tonnes: $E = \frac{1}{2} M V^{2}$ (kJ),
$V$ = approach velocity of the ship normal to the berth — commonly 0.10–0.30 m/s (larger for small ships or exposed berths; smaller for large ships in sheltered berths),
$C_{m}$ = added (virtual) mass coefficient, allowing for the water moved along with the ship — about 1.5–2.0 (e.g. Vasco Costa: $C_{m} = 1 + 2 D / B$ with $D$ = draught, $B$ = beam),
$C_{e}$ = eccentricity coefficient — the ship contacts the fender off its centre of gravity, so part of the energy goes into rotation: $C_{e} = \frac{1}{1 + ( l / r ) ^{2}}$ with $l$ = distance from the centre of gravity to the point of contact, $r$ = radius of gyration (≈ 0.2–0.25 $L$ ); typically 0.4–0.7,
$C_{s}$ = softness coefficient (1.0 for hard fenders, 0.9 for soft fenders),
$C_{c}$ = berth configuration coefficient (1.0 for open piled structures, 0.8 or less for a closed quay where a cushion of water is trapped).

The design energy is increased by a safety factor (1.25 to 2.0 for abnormal berthing).

Worked ExampleExample — berthing energy

A tanker of displacement $M$ = 50,000 t berths with $V$ = 0.15 m/s. Beam $B$ = 30 m, draught $D$ = 12 m, $C_{m} = 1 + 2 \times 12/30 = 1.8$ , $C_{e} = 0.5$ , $C_{s} = 1.0$ , $C_{c} = 1.0$ .

$E = \frac{1}{2} \times 1.8 \times 50, 000 \times 0.1 5^{2} \times 0.5 = \frac{1}{2} \times 1.8 \times 50, 000 \times 0.0225 \times 0.5$

$= 0.5 \times 1.8 \times 1125 \times 0.5 = 506 kJ$

With a safety factor of 1.5 the fender should be able to absorb about 760 kJ at its rated deflection.

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