Rossgraben Bridge

10 facts you need to know about the Rossgraben Bridge, designed by the great engineer Robert Maillart.
P.S. If you don’t know who Maillart is… raise your hand, but, you know, very discreetly. 🙃

Let’s go! 👇🏽

1️⃣

The bridge is a three-hinged reinforced concrete arch — meaning it has three joints or hinges: one at the crown (the top of the arch) and two at the supports.

2️⃣

The hinges allow small rotations of the arch to accommodate bridge movements. This typology makes calculations simpler and the bridge is less sensitive to soil settlements.

3️⃣

But…

The main drawback is the maintenance of the hinges. That is why this type of structure is not really used nowadays.

4️⃣

Since 1932.

It was built just two years after the Salginatobel Bridge and, as you can see, they look quite alike!
Enjoy this amazing photo from my colleague Carlos Polimón of one of the most known bridges out there (at least among engineers!).

5️⃣

The span (the distance between supports) is 269 feet (82 meters).

Alright, we’re halfway through. When you visit, share one of these facts with your friends, family, or anyone nearby. Let’s keep going!

6️⃣

The arch has an open-box cross-section that becomes closed when the longitudinal walls reach the deck. This way, all the elements work together to help the arch carry the loads.

📷 was taken from one end of the arch, between the longitudinal walls beneath the deck.

7️⃣

The arch section thickness varies along the length of the bridge.

8️⃣

Some technical data.

The arch rises 9.7 m, it is 3.6 m wide (widening to 4.6 m at the ends), and has a thickness of 180 mm in the middle and 200 mm at the ends.

9️⃣

To build it, Maillart came up with a design that was both efficient and cost-effective.

The arch was built on a wooden formwork. Once the concrete hardened, the arch and the formwork worked together to support the construction of the walls and deck. This way, the formwork was a lot lighter.

1️⃣0️⃣

The bridge underwent repairs in 2005, mainly in areas where concrete had spalled. A water-repellent coating was also applied to the surface to improve durability, among other improvements.

The photos were taken by me on a special trip through Switzerland.

I hope this inspires you to go see some bridges there, even if it’s just to enjoy the scenery. 🥰