Aside from design and technical puzzles to solve, what other challenges did you face?
I would say the development process. We were working with different disciplines within the city, such as traffic planners, maintenance, urban planners, as well as local stakeholders – businesses and residents. For me, it’s most important for people to feel co-ownership. Like the traffic planner city of Eindhoven, who concluded that it was OK to put the pylon right in the intersection’s center, he’s now a very active promoter of the Hovenring. With the local advocates, there was a lot of doubt and fear about the grades of the ramps. We actually invited them and other stakeholders involved on a little bike tour around Eindhoven to ride up different ramps and bridges – we didn’t tell them ahead of time what grades they were, but we’d measured them first. To everybody’s surprise, slopes that were thought to feel steep actually didn’t. So not only were people happy but they felt like they were part of the process. The Hovenring gradients are all a little different, but range from 2 to just over 3 percent.
Soon after the pylon was placed during construction, significant cable vibrations were noticed and you had to make adjustments. Was that a disappointment?
Not at all – we planned for that in the budget. Cable vibrations are to be expected in a cable-stayed structure such as the Hovenring, but in general are very hard to predict. We had set aside money in the budget to address the issue should it occur and ended up using less than we’d budgeted for. The solution was to use two types of dampers, high frequency and low frequency. By attaching them to the cables, it gave a counter vibration, solving the problem.
The Hovenring opened to great fanfare in the summer of 2012, and was immediately well used by residents. But the surprising attention was that photos and stories of the bridge went viral online and the Hovenring became an international sensation. How did that happen?
For some reason National Geographic discovered it and they sent a photographer, who made a beautiful picture. That photo went viral within the bike community. Later, when I did a presentation at Velo-city I met an influential cycling writer from England who wrote about it. And then Wired wrote about it and it just kept going from there. One wow thing led to another. It was quite special.
In many ways, the Hovenring has become your calling card. But the design is custom and not suitable for every location. How do you address that?
Because it’s such a high-profile project, I’m often asked to tour it with people or to go speak at different destinations and events. But what I usually do in talks is start with the Hovenring and then share what I’ve learned and how we applied this to other projects. In fact the people who invite me to speak are well aware that we’ve done a lot of different projects. They consciously use the Hovenring to attract an audience, but they specifically want to also talk about other projects and how they’re developed. Each project has a unique optimal solution.
What are you proudest of with the Hovenring? Do you feel it’s your engineering legacy?
All our projects start as a fantasy in somebody’s head. So, yes, it’s amazing and beautiful that you see your own fantasy become true and that other people like it. It’s really good to read that it inspires people to think out of the box or feel that things are possible. And it’s even nicer when you can explain to them that, yes, it looks nice but it was actually an efficient synergetic solution. Those things combined are what make it so special.
One of the things I like most about the project is that it is a truly integrated and synergetic design where structural and architectural elements are part of one solution rather than a layer cake of partial solutions that don’t hinder but also not strengthen each other. This is something we always try to accomplish. When you work at it, things can complement each other and be synergistic. That’s what the Hovenring was to me.
Also, by involving everybody, we ended up with a landmark that helped city branding and is comfortable to use. It’s great when that happens – you want this for every project. It’s the perfect example of what a good process can lead to.