Can glass bridges break under our feet?

Reading time: 2 min — Spotted on NewScientist, The Guardian

In Longjing, a city in eastern China, a tourist recently experienced a nightmare. Surveying a gigantic glass bridge located 100 meters above the void, the man saw the bridge break under his feet, fortunately taking refuge on a piece of reinforcement before being rescued a few minutes later. Unscathed, he was nevertheless taken to the nearest hospital so that his physical and mental state of health could be checked.

The rupture of several glass plates constituting the floor of the bridge is due to a succession of extremely violent winds (more than 150 km / h), specifies the Guardian. At NewScientist, we ask ourselves: should we fear that all bridges of the same kind will end up breaking too? Particularly popular in China (the most imposing of them, the Zhangjiajie Glass Bridge, is 430 meters long), these structures could cause major human disasters if they prove to be more fragile than expected.

The scientific journal took advice from Paul Bingham, a British specialist in materials physics, who says he is ready to cross any glass bridge himself. A way of saying that there is nothing to worry about for the other glass bridges of the world, even if it obviously calls on the design teams to be extra careful.

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Translucent but strong

Bingham points out that glass has two types of weaknesses: it is friable, and it is not composed of crystals, which makes the slightest crack almost impossible to stop. It is for this reason that it is generally coupled with a polymer which protects against its possible defects, so that if one of the layers breaks, the plate nevertheless remains intact.

Reinforced using potassium nitrate or thanks to a method based on the principle of thermal shock, the glass of the bridges actually has very little chance of breaking, adds the expert. "It's like trying to fill a washing machine with new clothes when it's already full," he concludes. "We can achieve this, but it creates a field of constraints that we must hit very hard if we want to succeed in breaking it". The accident of May 10, 2021 should therefore remain unique in the history of glass bridges.