Technology meets aesthetics

Glass is extremely strong and very durable as it neither corrodes, rusts nor rots. It’s also sustainable and completely recyclable. So why not put it to the ultimate test and build a bridge out of glass? Researchers who worked with Prof. Rob Nijsse, Ate Snijder, Joris Smits, Telesilla Bristogianni, Faidra Oikonomopoulou, Kees Baardolf, Christian Louter and Dr. Fred Veer asked themselves exactly that when they initiated the project at TU Delft. Together with colleagues and students, they developed the design and construction of the glass bridge. Glass tubes from SCHOTT were used as the building material.

Using glass as an outdoor building material places steep demands on it: “DURAN® borosilicate glass has high thermal shock resistance and stability. That’s exactly what an ambitious project like building a glass bridge needs,” says Klaas Roelfsema, Business Development Director at SCHOTT Tubing.

The 14-meter-long glass bridge, which can be seen and crossed on campus, proves two things: first stability and secondly, the material’s special aesthetic value. It fittingly forms the gateway to the “Green Village,” a test site on the university grounds that houses prototypes of sustainable innovations. Employees and students of the university as well as visitors can experience new technologies in action. Once all vulnerabilities are resolved, the prototypes are rebuilt at another location.

Even though the present glass bridge stands alone, it builds the trust for the next project – an arched bridge fully made of glass. The magical ice bridge from the movie Thor (2011) provides the inspiration. Its transparency and form gave the researchers the idea of experimenting with glass. The material’s transparency would create a unique aesthetic.

Technology of tomorrow

In an interview with Ate Snijder he discusses the construction of the glass trust bridge and the special processing of SCHOTT glass.

Why did you choose glass as a building material?

Originally, we thought of a steel structure. But that’s nothing new. We wanted the bridge to have a certain aesthetic. Glass has several advantages. It’s a very strong, durable and resilient material. It’s made of sand and can be recycled, which makes it sustainable, a complement for the “Green Village.” A glass bridge also means virtually no maintenance because it neither rusts, corrodes nor rots. On top of that, glass is affordable. Calculations and digital simulations finally showed that implementing our idea was actually possible. The fact that using glass as a construction material is still relatively new and hardly researched was one more reason for us as scientists to use the material.

What were your biggest challenges with the project?

We used a relatively new kind of material composition for bridge construction, first developed by Prof. Nijsse and technically conceptualized by Faidra Oikonomopoulou (see publication linked below) – glass rod bundles. We connected a star-shaped CONTURAX® glass tubes with six round DURAN® glass tubes. A transparent UV adhesive holds the tubes together. By making a bundle rather that a single glass rod, we create redundancy. If one, or even two or three rods in the bundle fail, the bundle as a whole still retains some load bearing capacity.

What are you taking away from the project?

Bundles of glass are safe for use in structures because of their redundancy since they can take damage without failing completely. They are also very strong in compression, comparable to steel or concrete. By prestressing the bundle, which means applying a compressive force on the glass, we can make sure that the glass bundle is always under compression, even if loaded by a tension force. But the bundles’ most important quality is their incredible aesthetics. To further optimize the glass bundles, we will test different configurations with and without glue.

SCHOTT has proven to be a great supplier throughout the project. We’re more than satisfied with the quality of the glass tubes and the service. We hope to keep our relationship open and work together in the future because we already have some exciting projects in mind. For instance, we want to expand the current glass bridge into an arched bridge. Students are also working with the glass bundles on a truss structure.

Impressions gained while building the glass bridge

Impressions of the stress-trest of the glass bridge

• More on SCHOTT Tubing
• More on the project
• Article in the trade magazine Innovative Materials
• Journal paper about design and experimental testing of the bundled glass column