Antwerp Dry Docks – Restoration of a dock gate
The Antwerp dry docks in the Hansadok and the dry docks near the city are the only remains of 200 years of tradition of ship building and restoration in the port of Antwerp. After years of decay, EDR hopes to transform the site into a new and modern ship yard, in partnership with with the port authorities. SBE is involved in the entire renovation of the site with 3 wet docks, 6 dry docks, warehouses, offices, workshops, cranes, etc., from master plan to detailed civil and mechanical engineering design.
Dry dock 5, the second largest and youngest dock, is the first to be restored. Its construction dates to the sixties and the dock dimensions are 240 m long, 40 m wide and 9 m deep. The steel gate (like a lock gate) is a sinking door and measures 41 m by 11,2 m and weighs approximately 170 ton. To be effective, this type of gate must be well balanced. It sinks into the water onto the bottom of the channel by only is relying on its own weight, rotating around hinges mounted on the concrete threshold of the dock. Due to well-placed water proof compartments within the gate, minimal force is required to hoist the gate upwards via a winch. These compartments in the gate create buoyancy, i.e. an uplifting force due to the Archimedes effect.
At first, the current state of the door was examined and mapped. Based on the building plans and a site visit, a program was set up to examine the gate. Dive inspections and measurements of the thickness of the steel elements were carried out. Critical components were carefully examined which led to the identification of two major problems. The door wasn’t sealing properly resulting in too much water leaking into the dock and the steel structure around the water line was heavily corroded.
With these conclusions, SBE went to work to find an economical solution. To solve the problem of the leak, it suffices to renew all the wooden support beams and rubber sealings. Because of years of wear and tear and incorrect maintenance, some beams don’t fit anymore onto the concrete edges to form a water tight seal, thus creating openings for the water to flow into the dock when it was pumped dry.
To tackle the problem of corrosion, a twostep solution was implemented: first a detailed calculation of the gate was made. A detailed finite element model was built in order to verify the gate. The steel structure can withstand the loading imposed on it, even according to modern standards and methods. But the lattice work around the water line is too heavily corroded and needed replacement. Due to its position on the door, it is situated in the highest zone of corrosion attack. It is alternately wet and dry, with lots of splashes from the waves and floating debris damages the conservation on the door, paving the way for severe corrosion mechanics.
SBE designed a new lattice work for the upper part of the door. After a thorough analysis an optimal and efficient design was obtained with careful consideration to lay-out and geometry to further reduce any chance of corrosion like a surplus of wall thickness on beams. To further protect the steel from corroding, the entire door will be fitted with a modern, highly performant conservation system that is also used in off shore construction where the same aggressive corrosion conditions apply. High demands for execution are set for the contractor in order to assure the quality, ranging from preparation of the steel surface over competent staff to quality of the paint.