Platform on civil engineering, underground infrastructure, energy, construction equipment & construction machinery
This includes the construction of a new flyover. Because of the unusual construction sequence, Dywidag was brought in to devise a unique solution for ‘stretching’ the deck.
In the existing situation, the slip roads and exits connect to the N391 Ring Road at ground level. Because of safety and traffic flow, the new traffic situation will require flyovers. The connection will therefore be reconstructed into a junction with flyovers. To minimize traffic disruption, the 93-meter-long flyover will be built in phases. “Normally a deck is built from left to right or from the middle, but here other ‘laws’ apply,” says Robert Jansen of Dywidag. “Because of the schedule and anticipated road diversions, the left part of the deck would have to be built first, then the right part and finally the middle part. Predictably not logical.”
It was up to Dywidag to make the nearly impossible possible anyway. “We took advantage of the fact that with 50% of end prestressing we can carry the deck's own weight. Fourteen channels were therefore installed in the first deck. Of these, seven remain empty and seven are filled and tensioned using couplers. So then the deck section is able to support its own weight. The box can be taken out from under it and the underlying road network can be shifted. The same trick was repeated for the other deck section, with the prestress shifted exactly one channel longitudinally. In this way, the middle section, which is now in progress, can thus be realized last. The cable in deck 1 is connected through the middle section to the open conduit in deck 3. Thus the decks are connected like a lacing. The entire deck is thus brought to a prestress of 100% in this way. There are no dilated joints, as they are completely compressed. The deck may ultimately be seen as one continuous prestressing. This phasing is fairly unique and actually occurs rarely if ever. But it can be done,” Jansen concludes.
