Nijmegen’s Waal bridge is a historical icon in the Dutch landscape: the 604 metre-long arched bridge has been an essential link between the cities of Arnhem and Nijmegen for over 80 years. At its inauguration in 1936, the bridge’s 244-metres arch span made it the largest in Europe. As a critical regional link, the bridge was strategically blown and rebuilt during WWII and had seen few interventions after becoming a national monument.
Around 50,000 vehicles and 5,000 cyclists cross the bridge daily and after 75 years of intensive use, the concrete deck needed replacement. So how do you safely extend the lifespan of this key listed bridge without impacting traffic flows?
Dutch roads authority Rijkswaterstaat appointed VolkerRail and KWS to lead the bridge renovation. Arup’s team of bridge experts was brought in to provide technical advice to the consortium, including advising on the design of the new concrete deck, the required steel repairs and structural safety.
80- year-old monument
244march span, longest in 1936 in Europe
Bridge owner Rijkswaterstaat was looking for an experienced and technically qualified team that could work collaboratively and ensure traffic impacts were minimised during the renovation works.
Arup’s bridge and highways engineers have a solid track-record when it comes to bridge renovations in the Netherlands, having worked as a partner for Rijkswaterstaat over the past ten years. Thanks to a strong collaboration with the VolkerRail and KWS consortium as well as the end client, our team has delivered a sound technical solution while mitigating traffic hindrances to ensure the successful delivery of this project.
Engineering the concrete deck
The existing concrete deck had lost its load-bearing capacity due to corrosion caused by de-icing salts and had to be replaced.
To allow traffic to continue to safely use the bridge, our engineers were asked to design a strong and safe concrete deck that would not jeopardise the existing steel structure.
©Thea van den Heuvel
The main challenges in the design of the concrete deck were complying with the weight limit without compromising on durability, while ensuring good alignment with the underlying steel structure, which presented several deviations due to old construction tolerances, the historical bombing and subsequent reconstruction.
Arup has integrated the design of the concrete deck and the steel repairs into a process focused on mitigating risk during construction. Our team has worked hard to help preserve this Dutch monument, while minimising traffic disruption. ” Daan Boddeke Associate Director
Fast-tracking the delivery to minimise traffic impact
Meeting the increasingly stringent requirements in terms of both the cover and load-bearing capacity presented a challenge. Taking into consideration the longitudinal and transverse steel beams, the new concrete deck now consists of more than 350 prefabricated panels which were assembled on site.
Every section is, in combination with repair, grid blasting and metallisation of the steel structure, completed in only one week. The usage of prefab panels also allows for good quality control while reducing construction time. This, in combination with the use of high-quality concrete mix, ensures durability will not be compromised. The result: a thin concrete deck of 190 millimetres, maximum reliability and minimal traffic hindrance during construction.
The steel structure could be assessed and mended in a short period of time thanks to a strict preparation process in which the expected damages and standard repairs were specified. A carefully managed, collaborative process between the consortium and the end client meant no unforeseen delays occurred during the replacement of the concrete deck.
Coordinating structural safety
Safety is essential across every stage of a bridge upgrade: the team worked to ensure the structural safety and guarantee safe crossing throughout the construction works. Although the role of Structural Safety Coordinator during construction was assigned to the contractor, the role was in this case fulfilled by Arup.
During preparation phase, Arup constantly checked and assessed the contractor’s workplans to guarantee the bridge’s structural safety, creating a more agile process with constant reporting back to Rijkswaterstaat, who remained responsible for the global structural safety. This set-up enabled a quality information flow, creating an effective, trusting collaboration to ensure the timely delivery of this safe bridge.