Continued safe use of the Merwede Bridge for many years to come

Maintenance Merwede bridge Gorinchem

The replacement and renovation task is one of the biggest infrastructural challenges for the coming decades. Many bridges, quay walls and other civil engineering works are approaching the end of their life. There are insufficient labour, material and financial resources to renovate or replace all the vulnerable elements of the whole at once. Nevertheless, our infrastructure must be structurally safe at all times. The Merwede Bridge near Gorinchem is a bridge that still needs to last a while as it is due for replacement in approximately ten years. So, an emergency repair of the suspension cables was necessary to ensure the continued safe use of the critical bridge.

During previous inspections of the Merwede Bridge, the embankment connection of the A27 between Gorinchem and Sleeuwijk, rust formation was found on the bridge’s suspension cables. That finding meant one thing: a necessary emergency repair to keep the road connection open.

Project management and supervision

Rust formation poses a severe threat: rust can cause irreparable damage in an advanced stage, whereby replacement is the only option. Of course, in the case of the Merwede Bridge, a vital link in our road network, this is not desirable right now. Rust was found on the 64 suspension cables of the bridge, called hangers. Iv was commissioned with the engineering company ARUP to work towards an implementation design. Iv also provided project management and supervision during the work. This had to take place over ten weekends, during which work was carried out 24 hours a day to minimise the inconvenience caused to vehicle traffic.
A team from the Directorate-General for Public Works and Water Management (WNZ, PPO and GPO), Iv, ARUP and the contractor combination STERK (with subcontractors Dywidag, Feijenoord and Smits Neuchatel) prepared and carried out the planning, specifications and realisation in a short time.

Maintenance Merwede bridge

Cableskin

Equipped with this team and knowledge, an implementation design was chosen to provide the suspension cables with ‘cableskin’: a protective layer that prevents rust formation. The Merwede Bridge is the first Dutch bridge to have this method applied. Only the bottom two metres of the cables are not provided with cableskin; instead, they have been given a new coat of paint (preservation). In addition, the so-called anti-vandalism caps, placed around the bottom two metres of the hangers, have been adjusted to improve waterproofness. Thanks to these measures, the hangers and the connection to the bridge deck and main girders are well protected against the effects of the weather in the coming years until the bridge is replaced.

Ad Heystek, together with various consultants and specialists, was involved on behalf of Iv in the emergency repairs to the Merwede Bridge, which were completed in November. At the end of last year, Iv was approached by the Directorate-General for Public Works and Water Management (Rijkswaterstaat) to conduct targeted technical inspections of the hangers and fasteners. In response to the report provided by Iv, action has been taken. Expert meetings were initiated to clarify the situation on the Merwede Bridge: what is happening, and what can be done about it?

“We were specifically asked because of our knowledge and expertise in steel structures, conservation, project management support and assessment during implementation,” says Ad. The technical support consists of answering several crucial questions, given the function of the bridge as an essential north-south connection: what is happening? What is needed to bridge the next ten years? How will we organise the work? And finally, what is the best management measure to apply without causing too much disruption to the immediate environment? These questions were weighed and answered using a trade-off matrix. The progress of the actual realisation was monitored with the TEKLA model developed by Iv. The status of each component and its associated documents are directly visible in this model.

Mission accomplished

In ten weekends, the work on the Merwede Bridge was carried out in both directions (Utrecht – Breda and Breda – Utrecht). This was the biggest challenge; according to Ad: “Combining phasing and determining the most suitable measures is essential. Given the required service life, what are the best measures to take while minimising inconvenience? That all went according to plan. The implementation and applications such as TEKLA were very well received by the Directorate-General for Public Works and Water Management. We are incredibly pleased about that.

This construction team-like setting was the basis for a successful approach. As a result, a supported solution was jointly realised in around eight months, from identifying the problem to design preparation and implementation. We can also apply this to other replacement and renovation projects. Key requirements include a proactive and responsive client (decision-making on the contractual, technical and environmental aspects), mobilisation and sharing of the right knowledge and expertise, and facilitation of the collaboration. And that, combined with a competent mix of contractors, has led to pragmatic solutions and an associated effective approach that has met the requirements well and efficiently. This will be necessary in the coming years.”

 

Curious about the possibilities for your project?

Wouter, managing director Infra and also COO of Iv, would be delighted to discuss this with you! Get in touch via +31 88 943 3200 or send a message.

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Wouter van der Wiel