Papendrechtsebrug: behind the scenes of the construction of the new bridge leaf

Although it will still take several months before the Papendrechtsebrug is closed to traffic, work is already well underway behind the scenes. Commissioned by the consortium Mobilis and Croonwolter&dros (CMCP), we have been working for quite some time at our yard in Krimpen on the construction of the new bridge leaf.

Patrick Bos, project manager at Hollandia Infra, gives us an update on the progress during a tour. He welcomes us at the entrance of the hall. A heavy door swings open, we descend a staircase and suddenly find ourselves in the middle of the work. “This is where we are building the bridge deck,” Patrick explains. “We had to wait our turn for a while, as we need the entire factory floor for this bridge. Now that a previous project has been completed, we can really pick up the pace.”

Anyone expecting to see one large structure will quickly notice that the bridge leaf is actually being assembled piece by piece. Various components are neatly arranged across the workshop. “Here we are producing the steel structure of the moving part of the bridge,” Bos explains. “This includes the deck, the ballast box, the tail sections and the main and cross girders. All the components are welded to the deck, like a very large construction kit.”

A thin deck for thousands of vehicles

At the far end of the hall, roughly 100 metres away, lies the bridge deck itself: a large rectangular structure measuring 23 by 33 metres, elevated about 1.5 metres above the ground. What immediately stands out is how thin the deck appears. “26 millimetres,” Patrick says when he notices our glance. “That may seem very thin, considering that thousands of vehicles will drive across it every day. But we reinforce this steel plate with trough stiffeners.”

He points to long steel V-shaped elements nearby. “We weld these underneath the deck along its entire length. On top of that we place cross girders. That way we make sure the bridge is strong enough without making it unnecessarily heavy.”

The weight of the bridge leaf turns out to be a recurring topic during the tour. Due to the increase in traffic volumes and vehicle weights over the years, the new bridge leaf will be significantly heavier than the current one. “We are going from 900 tonnes to about 1,500 tonnes,” Patrick explains. “Every kilogram matters. The heavier the bridge leaf becomes, the greater the impact on the existing substructure of the bridge, the bridge pit and the foundation. These were originally designed for the lighter bridge leaf currently in place.”

“To ensure the substructure of the Papendrechtsebrug can support the heavier leaf, the bridge pit and the support pier will be significantly reinforced. This work will take place during the bridge closure later this summer.”

Precision work with heavy materials

Further into the hall stands a steel structure that looks like a stack of boxes. Patrick jokingly refers to it as “the student housing complex”. “This is the ballast box, the counterweight of the bridge leaf,” he explains.

“The bridge deck is large and heavy. Without a counterweight, it would take a lot of energy to open and close the bridge in a controlled way. By adding this counterweight, we bring the system into balance so the bridge can move much more efficiently.” Each compartment of the ballast box is carefully filled with solid steel and concrete to achieve the precise balance required.

“When we install the bridge leaf on site, external factors such as wind will come into play,” Patrick continues. “So we will carry out additional measurements and testing during installation and fine-tune the weight distribution if necessary. It all has to be extremely precise.”

Lifting 40 tonnes

Back near the front of the hall, a massive steel component is being lifted into the air. The overhead crane indicates a weight of almost 40 tonnes. “This is one of the tail sections, part of the main girder,” Patrick says while pointing to the large steel plate. In the middle sits a thickened section with a hole in it.

“That’s where the bridge will rotate. The pivot axis in that plate carries the full weight and all forces from the bridge. A plate of 50 millimetres would simply not be strong enough. At the same time, making the entire plate thicker would make the bridge unnecessarily heavy. That’s why we only reinforce the plate locally.”

Transport

One obvious question arises while walking through the hall: how do you transport a 1,500-tonne bridge leaf to the Papendrechtsebrug? Patrick laughs. “That’s actually quite simple: by water.” Next to the hall, a new quay is currently being constructed. From there, the fully assembled bridge leaf will be rolled onto a large ponton barge.

“Once the reinforcement works at the Papendrechtsebrug have been completed, the bridge leaf can be transported. On site, we lower it into the bridge pit and connect the cables. That part is relatively quick.”

The real precision work begins afterwards. “We then have to adjust the bridge’s drive mechanism, consisting of the rack in the bridge pit and the pinions on the bridge leaf. That adjustment has to be done within tenths of millimetres. We will be working on that for three weeks during the night.”

Everything comes together

As we walk back towards the exit, sparks fly through the hall as welders continue their work. “The great thing about a project like this,” Patrick says, “is that you can really see everything come together. From individual steel components to a bridge leaf that will soon be used by thousands of people every day.”

“But before we get there, there is still a lot of precision work to do. So that next year we can assemble the Papendrechtsebrug like a perfectly fitting puzzle.”

Contractor consortium CMCP

The contractor consortium Mobilis and Croonwolter&dros Papendrechtsebrug (CMCP) is replacing the bridge leaf, drive mechanism and control systems of the Papendrechtsebrug on behalf of Rijkswaterstaat. For the steel bridge leaf and mechanical drive systems, the consortium has partnered with Hollandia Infra (construction of the bridge leaf) and Machinefabriek Rusthoven (mechanical components of the drive system).

Read more about this project here.