Circular portals 

Circularity and reuse are important themes in the widening of the A1 motorway between Apeldoorn and Twello. Heijmans also scores high on these topics when it comes to the traffic support structures (portals). For this, the contractor calls on GS Birkhoff Staalwerken, which specializes in the renovation, plug-and-play production and conservation of portals under one roof.

The cooperation between GS Birkhoff Staalwerken and Heijmans goes back many years. "We have also been part of the previous phases of the widening of the A1," says Henk van den Ochtend, director of GS Birkhoff Staalwerken. "Heijmans' ambition for this project is to reuse as many materials and raw materials as possible, or in other words to procure as little new material as possible. We only applaud that. Here on the A1, we put the puzzle together to approach that with regard to the required 35 traffic gantries as efficiently and economically as possible. That meant we only had to produce six new portals."

hefty spans

Reusing the existing gantries one-to-one was not an option on the A1, as the road is being widened. "The dismantled portals are first subjected to a thorough inspection at our site in Oude Tonge," Henk explains. "Then they are blasted and adapted to the new configuration. This may mean that we shorten them or actually lengthen them. We do the latter as much as possible with reused material from the A1 or from other Heijmans projects. The renovation portals all have a free span of between 40 and 50 meters, while the six new portals span between 50 and 60 meters. All portals are naturally built in accordance with the VDC 2012 standard of the Dutch Department of Public Works."

Everything under one roof

GS Birkhoff Staalwerken is a total supplier of portals and takes care of the complete picture for Heijmans, from engineering to on-site (dis)assembly. "We do everything under one roof: fabrication, blasting, preservation and pre-assembly," says Henk. "In this case, we prepare the portals in such a way that Heijmans can even install the cabling already at our factory. Then we assemble the background shields and suspension structure for a plug and play assembly on site. That too is sustainability, because everything is done indoors we don't have to unnecessarily drive up and down with long lengths. That saves a lot of transport movements. On site, we often work with several shifts simultaneously and guarantee the shortest possible lead time."

Proprietary conservation system

Speaking of a short lead time, GS Birkhoff Steelworks has developed a specific preservation system for portals that achieves final performance within 48 hours. "This enables us to move very quickly, which makes us truly unique," assures Henk. "In addition, we are certified for welding up to execution class 4. This allows us to strive for very high quality and we are involved in many extensive infrastructure projects, including the Oosterweel connection in Antwerp. For that, among other things, we make end plates and the zinc joint edging for the zinc tunnels." GS Birkhoff Staalwerken's specialism is not only appreciated in infra, by the way, as the company is also a renowned name in petrochemicals and offshore.