Floating jetties – The design of the outer harbour

 In Outer Harbour

In addition to locks and weirs, SBE is also familiar with other aspects of hydraulic engineering. A functional port or river needs more than just locks or weirs. For example, jetties and quay walls are often required. SBE has experience in the design of both jetties and quay walls. Quay walls can be described as reinforced, vertical walls as a border between water and land. Jetties are structures that are built in the water, based on piles: fixed scaffolding, or the water itself: floating jetties or pontoons. In this article we will briefly discuss jetties.

Jetty design on the Leie

On the Leie in Belgium there are some jetties for both professional and passenger shipping where SBE was aided the client from concept over design to realisation.

In order to make the river navigable for ships of CEMT class Vb (4 500 tonnes), at Comines the river needs to be modified. As part of the project, a new jetty for pleasure craft was designed. The intention is that passenger vessels can dock here as part of tourist excursions (90 tonnes – 35 x 5 m). SBE designed 2 pontoons of 24 by 2,5 m with connection to the quay. The major difficulty here lay in the fact that despite being a canalized river, there could still be some water level fluctuations. That is why two bridges of 33 m span were placed behind each other, one fixed and one mobile to follow the water level. Access to the jetty has been optimized in such a way that passengers can get on and off comfortably in all circumstances.

Further downstream in Machelen there is also a pontoon of 25,5 m by 4,5 m in combination with a mooring post for passenger vessels of 6,4 x 40 m. Here too, access was optimized via a combination of fixed and mobile bridge. In addition, a fixed jetty has also been built for commercial vessels (CEMT class Vb). This fixed jetty consists of tubular piles for mooring, connected with a few bridges to the land.

Jetty design on the Scheldt

SBE also designed jetties on the Scheldt, the largest Flemish river. One of the largest we designed so far was in Antwerp. In contrast to most other port cities where one arrives as a cruise tourist in the (industrial) port, in Antwerp you arrive in the city centre after having sailed up the basin of the Zeeschelde. However, this also presents some challenges if Antwerp wants to construct a new terminal. The current terminal is outdated and totally unsuitable for modern cruise ships. The ships are still mooring at the quay wall, which causes a lot of problems due to the tides.

Together with the various administrations and the architect, SBE designed a floating jetty for both inland cruise ships and large sea cruise ships. Quite a challenge since there were some preconditions such as architectural design, technical challenges such as high-water level variations and strong currents, the environment with its historic quay walls and buildings, high usage requirements, … Three massive pontoons of 120 m long and 9 m wide where to form the landing stage for the cruise ships. These pontoons are held in place via large tubular piles. Two smaller pontoons, one in the north and one in the south; are the link between the access bridges and the mooring pontoons. This connects the ship to shore without transferring the mooring forces towards the bridges or quay walls.

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Design of fixed jetties

SBE has also completed the design of fixed jetties. BASF Antwerp chose SBE as a long-term partner for its civil engineering division. Part of this contract is the maintenance and expansion of the BASF Antwerp jetties. Loading and unloading finished products and raw materials through their jetties in the docks of the port of Antwerp is a vital business component. Some jetties have already reached a considerable age. They require maintenance or renovation to satisfy safety and to keep loading and unloading capacity high, in accordance with the latest standards and processes. SBE always assists BASF with their experience such as drawing up maintenance plans with inspections and measurements, calculating new loading and unloading platforms or checking existing structures that are modernized with new equipment.

Even for boards with a background in civil engineering or its own civil engineers, jetties are very specific structures with a separate problem that requires the necessary attention. SBE has cooperated on many jetties and has built up significant experience. Together with our experience in other fields of hydraulic engineering, we can assist our customers from concept over design, to the realization of a jetty to achieve optimum results for them.