Senior designer and project leader Adriaan Kok is one of the designers of the Hovenring. In this interview by Diane Daniels, he tells us all about the challenges involved.
What was the goal of the Hovenring and how did you address it?
There were many. The original intersection was a big roundabout used by all modes of traffic that was terribly congested and not well designed for cyclists. Eindhoven recognized that this junction was an important crossroads, joining with Veldhoven and Meerhoven; was on the way to the airport; and was near the A2, the country’s most important north-south highway. Also, the city focuses on innovation and technology and is known as the City of Light, as it’s the birthplace of Philips. Eindhoven is really aware of its city branding and wanted this bridge to be innovative, to use light creatively and to fit in visually with existing local landmarks such as the Evoluon, a futuristic saucer-shaped building up the street.
Where did the idea to build a suspended roundabout come from?
First, we did what we always do – getting the requirements of everything involved. We sketched and designed various alignments to figure out what would be the most efficient and comfortable and cause the least hindrance for existing traffic. We came to the conclusion that an elevated roundabout with four connecting bridges offered comfortable and direct routes and could be built within the existing roundabout area below it. This offered us the chance to create a flying saucer like design that elegantly refers to the Evoluon building. As the idea grew, people got more and more enthusiastic.
How did you figure out the technical components to make it work?
There were many technical challenges. For the bridge itself, we wanted an efficient structure with a thin, circular bridge deck. In essence, we were looking for a clean and simple concept of just a circular deck and a central pylon. By only attaching stay cables to the inner side of the bridge deck, where it connects to a circular counterweight, torsion within the bridge deck is limited. The ring on the inside is partially filled with concrete, which acts as a counterweight and balances the bike deck. So on the outside you have bridge deck and on the inner side you have stay cable and counterweight, which balances the deck around the stay cable. It’s a well-balanced and efficient structure, which significantly reduces the amount of steel needed. Cost wise that’s also a good thing.
Overall, I don’t think a structure like this one has ever been built before. Convincing all stakeholders and disciplines involved of the fact that this new design was efficient and could meet all the requirements was a challenge but we succeeded. I am proud that we made it happen.
Another challenge was spatial integration. The existing infrastructure and buildings set the boundaries for the grades of the slopes leading up to the roundabout. As space was limited, it was decided to lower the ground level of the intersection underneath by a meter and a half, allowing for a comfortable slope for pedestrians and cyclists.
Also, on the ground, we needed to place the central pylon in the middle of a very busy crossing. I had the impression it would be possible but we had to ask the Eindhoven traffic planner. Luckily and to my happy surprise, he agreed with me.
The lights around the structure are really spectacular. How did you decide where to place them?
We realized that the space in between bike deck and counterweight was a logical place to put lighting. We filled that gap with translucent sheeting and tubular lights, creating a ring of light that also would fit in with the urban planners’ goal of creating a special lighting effect. At night the ring of light is clearly visible. Together with the illuminated pylon, the lighting certainly lives up to the City of Light name.