Rebuilding the heart of the Papendrecht Bridge

It is a conventional steel bascule bridge with a 30-metre single-leaf drawbridge that opens for taller vessels, with a bascule pit underneath the movable span.

The bridge carries traffic on the N2 across the Beneden Merwede river, opening about 900 times a year to allow the higher vessels through. It is also a vital connection between the A15, A16 and Drechtsteden region, and one of Europe’s busiest inland waterways.

And now the mechanical heart of the bridge is coming to the end of its technical life, which means the Dutch water board – the Rijkswaterstaat – is planning a complete overhaul in what it says is one of the most technically demanding replacement projects on the go in the Netherlands today.

Technicalities

The existing movable span measures around 30 metres, but increasing traffic loads over almost 60 years mean a substantially stronger structure is now required. The new bascule leaf will be about 50 metres long and 23 metres wide and weigh around 1,450 tonnes, which is more than 500 tonnes heavier than the existing 900-tonne bridge leaf.

That increase in weight has consequences beyond the steelwork itself, requiring strengthening of the bridge pier, the bascule pit and surrounding civil engineering works before the new structure can even be installed, Rijkswaterstaat says.

Hollandia has been contracted to build the new bascule leaf, which starts with a thin steel deck plate that will have longitudinal trough stiffeners welded to its underside before massive girders are connected , forming the structural backbone.

“Here you see the deck that traffic will eventually drive over,” said Project manager Patrick Bos during a Rijkswaterstaat site visit. “It looks like a simple steel plate, but troughs are built onto it, creating a thick structural package that gives the deck its strength.”

Perhaps the greatest fabrication challenge comes from the sequence in which the bridge must be assembled. Around 80 to 90 per cent of the welds are initially completed on what will ultimately become the upper surface of the bridge. This means the partially completed structure – already weighing around 700 tonnes – must eventually be rotated before final welding and assembly can continue.

Weight and precision

Weight management is another critical engineering challenge. Although the new bridge is considerably heavier overall, every kilogram must be carefully justified. The bascule leaf rotates around a massive pivot shaft, concentrating enormous forces into relatively small areas. Hollandia’s solution is to increase thickness only where structurally necessary.

“All the forces pass through this relatively thin plate towards the pivot point,” Bos says, pointing to one of the bridge tails. “Locally we need a very large thickening where the shaft passes through, but we don’t make the whole plate thick, because then the bridge would become far too heavy.”

Precision manufacturing is equally important. Unlike a conventional fixed bridge, every component of a bascule bridge must align perfectly with its mechanical systems, bearings and counterweight geometry.

Small dimensional errors can translate into significant operational problems once the bridge begins opening and closing hundreds of times each year.

The project extends well beyond the bridge leaf itself. Mobilis & Croonwolter&dros (CMCP) is replacing the complete drive system together with the electrical installations used for operation, control and monitoring.

A new technical room will be added to the bascule pit to house modern control equipment, while the existing bridge operator’s cabin will disappear as bridge management becomes increasingly centralised. Concrete repairs within the bascule pit and strengthening of the supporting pier complete the structural package, and will be carried out by Hollandia.

Logistics

Delivering the work presents major logistical challenges. The Papendrecht Bridge is one of the region’s most important road links while also serving as the only access route for high shipping travelling towards Gorinchem. Rijkswaterstaat therefore developed a construction sequence that attempts to balance disruption between road users and navigation.

The movable span will be removed as early as possible in the programme, allowing major structural works to proceed while creating limited monthly passage opportunities for high shipping. Road traffic, however, will face a full closure of approximately nine months during the main construction phase.

The project also demonstrates the growing emphasis on standardisation within Dutch infrastructure renewal. By retaining the same client, contractor consortium and specialist suppliers that successfully completed the Haringvliet Bridge renovation, Rijkswaterstaat aims to reduce programme risk while preserving valuable engineering knowledge across multiple bridge projects.

The renewed Papendrecht Bridge is due to reopen later this year.