[Image above] Credit: Researchers surveying the inside of a newly constructed inflatable concrete dome developed at Technische University Wien. Credit: TU Wien
There’s a long history of engineers, designers, and innovators using inflatable structures to mold concrete.
While they can be fun and funky in their designs—and eco-friendly, because they save building materials otherwise needed to construct a mold—many of these methods produce structures that aren’t quite reliable, due to inconsistent application of the concrete and lack of structural supports.
But researchers at Technische Universität Wien (Vienna, Austria) have devised a method to mold flat, precisely designed concrete geometries and then inflate the hardened slabs off the ground to form 3-D concrete domes. And the researchers continue to perfect their method for making larger, more efficient inflatable concrete structures, according to a recent TU Wien press release.
“It is similar to an orange peel, which is regularly cut and then flattened out on the table,” researcher Johann Kollegger says in an earlier press release about the work. “We do it the other way around, starting with a flat surface and then bending it to a shell.” Kollegger and colleague Benjamin Kromoser designed the concept, which they call pneumatic forming of hardened concrete.
After hardening the flat concrete slabs, post-tensioning tendons hold the structure in place at its circumference as its inflated off the ground. Glass fiber-reinforced plastic tendons help absorb strain in the hardened concrete slabs as they bend into place.
The team has already built and inflated several successful curved structures with their method, and most recently completed test construction of a still larger dome structure. The new dome—26.5 m long, 19.1 m wide, and 4.2 m high—weighs 80 t, but had no problem being lifted into place with the help of an inflatable bladder.
Watch this short time-lapse video to see the structure inflate into its final domed shape.
Credit: TU Wien; YouTube
For more information, see the TU Wien team’s open-access publication in Advances in Materials Science and Engineering, “Pneumatic formwork systems in structural engineering” (DOI: 10.1155/2016/4724036).