The work on the Kooybrug is well underway. Since October 2024, the main roadway has been renewed, and the parallel road is ready for use. Why then is it necessary to close the bridge for 28 nights? The answer is simple: testing, testing, and more testing.
Guido Aschman (technical manager and test manager at contractor VolkerWessels) and Art Warmenhoven (technical manager at Rijkswaterstaat) explain the importance of the testing work.
Adjusted movement works, a new electrical installation, and new traffic signals are just a few of the works carried out over the past six months, allowing the Kooybrug to last for decades. Provided everything works well.
Aschman: ‘We want to be absolutely sure that all technical systems are fault-free before we reopen the bridge. Suppose the bridge needs to open for a cargo ship. Then the signals must be on, the barriers must go down, and the bridge deck must go up. If the barriers or signals respond too late or not at all, it leads to dangerous situations. To ensure safety, we test everything until it works perfectly.’
The Importance of One Cable
‘There is no second Kooybrug,’ Warmenhoven emphasizes. ‘Everything is uniquely made or programmed for the bridge: from the length of the bridge deck to how it opens. So we test everything, working from the details to the big picture.’
‘Yes, we really start at the basics,’ Aschman agrees. ‘Are the cables properly connected? Does the motor turn in the right direction? That level. Then we focus on the dozens of subsystems, such as maritime and road traffic signals. We test them independently. Only then do we test everything integrally. We look at, among other things, the order in which the subsystems react: first the traffic signals, then the barriers, then the bridge deck, and so on.’
Time and Focus
Conducting hundreds of tests takes time. ‘And focus,’ Aschman adds. ‘We can’t keep interrupting a test to let traffic cross the bridge. That is not only inefficient but also unsafe for the workers. They sometimes have to stand right on the bridge to see if something works.’
Warmenhoven: ‘Besides wanting to ensure a safe working environment, we also want to minimize disruption to traffic. This requires some balancing. We try to test as much as possible while traffic is on the bridge. For example, we check the mechanism of a barrier cabinet without the arm.’
‘But sometimes it’s just not possible to avoid closing the bridge, such as when testing the bridge deck. That’s why we’ve planned 28 night closures in March and April. This number is based on the minimum time we need to test everything, plus a buffer for when tests go wrong.’
Hard Work for a Beautiful Goal
We have taken other measures to minimize disruption. ‘Early on, we digitized the bridge and its systems,’ says Aschman. ‘We can already test whether each subsystem works on paper in this environment. Of course, everything is a bit different in reality, but we can build in some certainty this way.’
‘We also maintain intensive communication with the surrounding area,’ Warmenhoven adds. ‘For example, we combine the passage of freight transport over water from Oostwouder with testing the bridge. It’s a big job, but luckily we’re working together towards a great result: a fault-free bridge, keeping Den Helder well connected with the rest of the Netherlands.’