Architecture

New construction technique allows concrete domes to be "popped up"

New construction technique all...
Inside a test dome built using the pneumatic wedge method
Inside a test dome built using the pneumatic wedge method
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Inside a test dome built using the pneumatic wedge method
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Inside a test dome built using the pneumatic wedge method
First, a number of flat rebar forms are laid out side-by-side on the ground at the building site, on top of a deflated plastic air cushion
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First, a number of flat rebar forms are laid out side-by-side on the ground at the building site, on top of a deflated plastic air cushion
Concrete is then poured into those forms and allowed to harden, resulting in a series of flat slabs
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Concrete is then poured into those forms and allowed to harden, resulting in a series of flat slabs
Metal beams and a steel cable are subsequently attached to those slabs, linking them all together
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Metal beams and a steel cable are subsequently attached to those slabs, linking them all together
As the air cushion inflates, it lifts the slabs up from underneath, causing them to bend with it in the process
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As the air cushion inflates, it lifts the slabs up from underneath, causing them to bend with it in the process
Austrian Federal Railways has already commissioned a design for a wildlife overpass that incorporates the technology
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Austrian Federal Railways has already commissioned a design for a wildlife overpass that incorporates the technology
The technique could also be used to build structures such as band shells
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The technique could also be used to build structures such as band shells

There probably aren't many domed concrete structures where you live, and there's a reason for that – they're difficult to build. Doing so usually requires the construction of a supporting wooden structure, that holds the concrete in place while it hardens. Now, however, a team at the Vienna University of Technology has devised a system that allows concrete shell structures to simply be "inflated" and cinched together with a steel cable.

Called the pneumatic wedge method, the technique has been likened to peeling an orange and lying its skin flat on a table – except in reverse. Here's how it works ...

First, a number of flat rebar forms are laid out side-by-side on the ground at the building site, on top of a deflated plastic air cushion (see the photo below). Concrete is then poured into those forms and allowed to harden, resulting in a series of flat slabs. Metal beams and a steel cable are subsequently attached to those slabs, linking them all together.

First, a number of flat rebar forms are laid out side-by-side on the ground at the building site, on top of a deflated plastic air cushion
First, a number of flat rebar forms are laid out side-by-side on the ground at the building site, on top of a deflated plastic air cushion

Next, the dome-shaped air cushion is inflated. As it fills with air, it lifts the slabs up from underneath, causing them to bend with it in the process. At the same time, the cable is tightened in order to snug them in against one another, with the connecting beams ensuring that they all move in unison. All of the slabs have wedge-shaped edges, that allow them to securely interlock with their neighbors.

Once the shell is up, the air cushion is deflated and removed, and the beams and cable are taken off. The bending of the hardened concrete does cause some small cracks to appear, but these reportedly don't affect the stability of the structure. "If the shape is right, each stone holds the others in place and the construction is stable," said project co-leader Prof. Johann Kollegger.

As the air cushion inflates, it lifts the slabs up from underneath, causing them to bend with it in the process
As the air cushion inflates, it lifts the slabs up from underneath, causing them to bend with it in the process

Finally, the whole thing can be covered with a layer of plaster, adding a bit more strength (and perhaps also keeping people from wondering about those cracks).

In a test of the system, a concrete dome measuring 2.9 meters (9.5 ft) in height was built in approximately two hours. According to Kollegger, shells of up to 50 meters (164 ft) in diameter should be doable. The other project leader, Benjamin Kromoser, believes that the technique should reduce the construction costs of such buildings by about 50 percent – along with savings in time and materials.

Austrian Federal Railways has already commissioned a design for a wildlife overpass that incorporates the technology.

Time-lapse footage of the construction of the test dome can be seen in the German-language video below.

Source: Vienna University of Technology

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16 comments
exodous
K.I.S.S. This is far more complicated than what a company called Mololithic Dome for like almost 50 years.
Jim Bruin
Hate to burst your concrete bubble, but they've been inflating concrete domes since the mid 1960s. The work was pioneered by Dante Bini. In fact, there are numerous companies that design and build custom inflatables and provide materials and plans for concrete domes. To be honest, I can't see any advantage of this method over existing inflating methods. Anyone know what the advantages are?
James Gattis
Personally I like this method better than the one detailed in the article: www.monolithic.org No cracks and the entire structure is one solid piece. Plus it's been in use for years already. Also a question - the article here states a test structure was built in approximately two hours... Does this include the time needed for the concrete to harden?
Richard Braisby
How do these domes differ from the domes that popped up like mushrooms all over the place in the 1960's called Binishell Shell Domes. And due to the lack of progress in this area they seem to have failed. http://failures.wikispaces.com/Binishell+Domes
Rt1583
"In a test of the system, a concrete dome measuring 2.9 meters (9.5 ft) in height was built in approximately two hours." That statement is an outright lie. It may have taken approximately two hours to raise the structure from flat on the ground to its usable height but there is no way that everything was done in two hours.
Mario Maio
1600 concrete structures were built with the Binishell system (patented by Dante Bini) all over the world. In my area, Tuscany, I've seen many of them (Dante Bini studied architecture in Florence): http://en.wikipedia.org/wiki/Binishell
yrag
I have to agree with other commenters here, this article is decades late and a dollar short. The Vienna University of Technology may have added some improvements to the general technique (although they got to be fairly mild or subtle) but this entire process has been used for decades. This article might be of some interest to those unfamiliar with this technique, but 'new', hardly.
flylowguy
The technique of using an inflatable rubber dome form for successive layers of Gunite applied concrete mix has been in use since the late 50's. Early on, there was some successful work done concurrently with the inflatable dome forms using a high proportion of short pieces of steel wire clippings in the mix for additional strength and cohesion, therefore leaving the traditional hand-placed and tied rebar out entirely.
jerryd
This is completely different than monolithic versions with various advantages and disadvantages. Here the bag is used for lifting only vs the shape for the mono. It's far easier to place the concrete, finished the one here simply by pouring it vs a gunnite gun, etc needed for the monolithic. I like the Mono too but the posts here are out of line. Can't you be happy there is another choice instead? As for the example I can think of several better ways to do structures with this raising system. I'd go for a flat without cuts into a U /vault style building and raising to place. I'm fairly handicapped and I could do such myself in 1 day to set up, pour, another to inflate into position, put in end caps with doors, windows, etc. Selecting the right 'cement' is key. I certainly wouldn't be using standard concrete with this.
Jim Sadler
There is an English company that has a blanket system filled with some sort of cement or concrete and fibers. The pneumatic tubes cause it to take shape and the fabric is then made wet with a garden hose. No rebar is required. I like it better as the shape looks a bit more normal than the domes shown and it is easier and faster to to erect. It is good in combat zones and is very resistant to wind storms and rather permanent in nature. Cracking is not an issue. It is also strong enough to allow a bulldozer to pile dirt several feet up the walls for extra protection.