A new kind of bridge manufacturing method, nicknamed the umbrella method, has been introduced in Germany, and it promises an entirely new, revolutionary way to span bridges without extensive scaffolding.
The bridge is built like a closed umbrella: a tall structure standing at the center of the bridge span. But instead of umbrella spokes sticking out from the sides, the tall structure unfolds slowly, stretching the spanning steal girders into place. It’s something that must be seen to believe, and here’s a link to the YouTube video of it working in Germany. Watch the video here.
“Erecting bridges using scaffolding usually takes months,” designer Johann Kollegger said in a statement. “The elements for the balanced lowering method, on the other hand, can be set up in two to three days, and the lowering process takes around three hours.” But this process, he says, is less invasive for bridges through protected or uneven terrain. The team's sample bridge over the Lafnitz River touches a nature preserve.
The bridge has a span of about 72 meters (236 feet) which is plenty wide enough to span roadways and rivers. And if that span is not long enough the process can be “daisy chained” to connect longer bridges.
Each girder weighs 50 tons and they’re lowered slowly and methodically. The girders, once in place, are filled with concrete, with the implication being that they’re faster to build and stronger overall (if you can get your hands on the equipment.