Renovation of Berlage Bridge Amsterdam: Temporary bridge with bayonet closure under soil

In the space of sixteen weeks, the monumental Berlage Bridge in Amsterdam is undergoing a major renovation. The 1932 bascule bridge, an artery in Amsterdam's infrastructure, was showing signs of trouble and no longer met the safety requirements set by law. To this end, the Combinatie Berlagebrug (Mobilis TBI and Rusthoven) is installing a new movable bridge section and installing new bridge technology. At the same time, monumental parts are being restored. To make this possible, Voorbij Funderingstechniek and Retro Bridge, commissioned by Mobilis TBI, have constructed a temporary bridge for pedestrians, cyclists and emergency services. Other traffic will have to make a slight detour.

The temporary bridge is on the north side of the Berlage Bridge and consists of ready-made bridge sections that bridge the Amstel River via two abutments and two intermediate piers. "The division of tasks in this was very clear," says Marco Vlasveld, chief executor of Voorbij Funderingstechniek. "We provide the foundation and the steel supporting structure for the temporary bridge, Retro Bridge then installs the modular bridge sections on top of this, and in December we dismantle everything in reverse order. We have done projects together before so we are already in tune with each other."

Drill

The auxiliary bridge has a foundation of steel casing piles (diameter: 406 mm) with welded-on drilling points. Vlasveld: "All the work is done from pontoons, including drilling the piles. Piling and vibrating were not allowed because of the risk of damage and nuisance. On the total of twenty piles, which protrude about 10 cm above the water, four steel support structures for the bridge sections were welded. These were prefabricated in our welding and construction hall in the Western Port area based on Mobilis' specifications. In May, these sections were ferried to the work site in Amsterdam."

Bayonet closure

Municipal regulations tell us that it is not allowed to stir the river bottom, let alone dig into it, and that in connection with shipping, nothing should protrude from the bottom. But also that well below the ground level, everything must be removed afterwards. "That makes it mildly difficult to remove a temporary foundation," Vlasveld observes. "Working with culverts in this environment was also not an option. So we came up with a new solution: a foundation pile in two parts. Up to one and a half meters below the bottom is the lost part, above that a part made removable by a kind of bayonet connection. That was made with a cam attached to an inner tube on the top tube, which is secured in a bayonet recess of the bottom tube. In December, we will hopefully unscrew that one easily as well. Everything is well greased and sloped. If it works, we will use this more often because you limit your lost foundation by doing so."

The steel support structures of the bridge sections were placed on notches in the casings. Vlasveld: "That went carefully until the sections were level and aligned. Then everything was welded together and Retro Bridge was able to hoist the nine bridge sections - three times three - onto them and connect them together. As with all projects, our emphasis is on safety and stability. The bridge stands like a house and when we are finished in December, there will be nothing at all to see."