Where in Zuidas
Except for three formidable cranes – the tallest one reaching 85 metres into the air –there are few visible signs at street level of the building work that is going on at The Pulse of Amsterdam. From the A10 motorway, you might catch a glimpse of the twenty huge pipes between the sheet piling, but apart from that there’s nothing to be seen. However, six metres down, contractors VORM Bouw are working hard on perhaps the most important part of this new, multifunctional building: the foundations. We went to take a look at the building site with Arie van Zessen, foreman for VORM Bouw.
Steel mesh reinforcement
As soon as we descend into the construction pit, you just can’t help noticing the steel bars everywhere, forming a kind of 3D grid. These are the reinforcement bars, explains Van Zessen. In some places they rise up in an intricate pattern to form a kind of cube. ‘As you can see, we’re busy working on the steel mesh reinforcement’, says Van Zessen, pointing to one of the forms. The steel bars are being meshed together to make a kind of skeleton. ‘Then we build a formwork around it, which is a kind of mould that we pour concrete into, creating solid blocks. So the purpose of the steel bars is to strengthen the base that will support the building.’
Vibrant and sustainable
The Pulse of Amsterdam will be one of the stars of the show in Zuidas. The two unique towers rising to around 80 and 90 metres high will be connected via the lower section of the building, on top of which there will be an urban forest. The Pulse will be part of a cluster of buildings surrounding a verdant, public inner courtyard area. The complex will house 200 apartments: 151 mid-sector rental homes and 49 private sector homes. There will also be 36,000 square metres of office space, and facilities such as a cinema, hospitality venues and a supermarket. The developers VORM and EDGE are determined to make The Pulse a lively addition to the Kenniskwartier. Sustainability is a top priority: the building will be completely self-sufficient and energy neutral.
700 tons of steel reinforcement
A few moments later, as we walk back across the construction pit, Van Zessen points to a large pile of long steel rods. ‘Those are part of the reinforcement for the base of the office tower’, he explains. Some of the support structures – specifically those for the residential tower – are already in place, but one larger support base for the office tower is still being created. ‘It’s all to do with the design of the building. A different load-bearing capacity is required for this section’, says Van Zessen. ‘We need 700 tons of steel reinforcement for this one section. That’s 23 truckloads of steel bars! Have you tried lifting up one of these steel bars?’ He smiles as I have a go. ‘Pretty heavy, isn’t it? That’s why we use a crane. You couldn’t get all those bars into the construction pit manually.’
Multi-stage process
Work on The Pulse started back in August 2021 with the installation of the sheet piling around the construction pit. ‘It’s a cliché, but the foundations really are the most important part of the building’, explains Van Zessen. He patiently explains the different phases in the process. ‘Before you can start digging, you first need to pump out the groundwater.’ He shows me a white pipe that runs out of the construction pit towards a pump. The water that is removed through that pipe is pumped back into the ground a little further up. ‘And by the way, you have to carry on pumping the water out continuously’, he explains. ‘Otherwise, the whole pit will be an enormous swimming pool before you know it.’
Combi-piles
After the sheet piling is in place, you can start driving the foundation piles into the ground. That involves combi-piles – a special system that allows you to place the foundation piles with a minimum of noise and vibration. How does it work? ‘First you screw a steel tube into the ground, which forms a kind of shaft. Then you push a prefabricated concrete pile down inside it, which you fill around with concrete. Then you remove the tubular steel pile again by turning it in the opposite direction.’ After the pile driving, the next stage is to excavate and pour the work floor. Then come the reinforcement bars. ‘You need to create the work floor first, because otherwise the reinforcement bars would just sink into the sand’, explains Van Zessen.
Timetable
The foundations are expected to be complete by early April 2022, after which work can start on the basement walls. The Pulse of Amsterdam is scheduled for completion at the end of 2024.
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