Three Potain MD top-slewing tower cranes are helping to construct 18 reinforced concrete “caissons” that are required as part of the design and construction of the new Portier Cove eco-neighbourhood in Monaco. Started in 2016, Portier Cove is a €1.36 billion plan that will see six hectares of land reclaimed from the sea, upon which 60,000 m² of housing, an extension of the Grimaldi Forum and a coastal promenade will be built.
French company Bouygues Travaux Publics (Bouygues) has been contracted to build the foundations of the offshore extension, including 18 reinforced concrete structures that will act as underwater struts. Known as caissons, these hollow, cylindrical chambers are being made in the Marseille-Fos Port in France before being towed to Monaco where they will be positioned and reinforced by infill.
To create the 10,000 t, 26 m-high structures, the contractor is renting a vast proportion of the French port, including a 10,000 m2 caisson precasting zone, as well as a 32,000 m2 area of water, where a floating dock is positioned. A first in France, this 56-m-long, 50-m-wide and 27-m-tall floating dock will make it possible to assemble the caissons before they are delivered to Monaco.
It is here that three Potain top-slewing tower cranes are working over a period of 24 months: two brand new Potain MD 569s to help construct the caissons themselves and one MD 560 B for general supply of the shipyard from the harbour dock.
Floating but fortified
The two MD 569 tower cranes – erected at heights of 45 m and 59 m – are positioned on the water on floating platforms known as “pilotis.” This presented a challenge for Bouygues, as not only are the pilotis required to support the cranes when lifting heavy loads, such as 25 t reinforcement cages, they also need to remain secure when battling the sea and the notoriously strong winds of the region.
The contractor worked with Manitowoc’s tower crane Lift Solutions team to find the answer. The Lift Solutions team consists of engineering and servicing experts that are dedicated to helping customers with unique and customized applications for their cranes. The team developed several pylon compositions specific to the site, combining different types of masts and chassis to increase the height and safety of the cranes. It also provided adapted load charts to account for piloti movement possibilities in all weather conditions.
The MD 569 is particularly well-suited for challenging jobsites. The crane is part of the new MD range equipped with Manitowoc’s CCS (Crane Control System), enabling it to optimize load curves while maintaining maximum lifting speeds. Both MD 569 cranes on-site are also fitted with CraneSTAR Diag, which provides constant, up-to-date crane fleet information. Operators can monitor locations and working conditions; plan maintenance and lifting schedules; and maximize efficiency, productivity and profitability.
Jean-Claude Guiter, sales director at Manitowoc, said: “Bouygues chose these cranes because of their superior quality, load capacities and heights. The cranes’ performance has even led to the sale of another MD 569 in the port of Marseille. By taking on projects of this magnitude and complexity, Potain demonstrates its ability to provide top-of-the-line cranes, as well as superior engineering and customer support, no matter the demands of the work site. What’s more, this is nothing special; it’s all part of our standard package.”
Expanding a city
Work on the caissons began in 2017 and is due for completion in 2019. Once complete, they will be towed to Monaco where they are run aground to form the foundations of the offshore extension. They will then be ballasted with sea water and weighted with quarry material. Each caisson façade has been specially designed to accommodate sea flora and fauna. Once the caisson belt has been finished, construction of the reclamation ground begins. The entire Portier Cove project is scheduled for completion in 2025.
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