Researchers at TU Wien have developed a construction method for concrete domes, requiring far less amounts of labor and materials than the conventional resource intensive formwork. Invented by Dr. Benjamin Kromoser and Prof. Johann Kollegger at the Institute of Structural Engineering, the new method is called "Pneumatic Forming of Hardened Concrete (PFHC)" and sets the complicated spatially curved formwork and the framework unnecessary. Also important is that it saves up to 50% of the concrete as well as 65% of the necessary reinforcement steel.
How it works
First of all, a flat concrete plate with wedge-shaped outlets is casted, whose production has to be done with high accuracy in order for the final shape of the cell to be precise. Once the concrete is hardened, a simple air cushion is placed underneath the plate and is filled with air. The post-tensioning tendons at the circumference are tensioned until the plate is turned into a double curved shell, while the occurring strains are absorbed by glass fiber reinforced plastic rods used as reinforcement.
Test dome construction
A test dome on a scale of 1:2 is currently being built in Carinthia, in the south of Austria, on behalf of the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur), as the company is interested in using this construction technique on a deer pass over the twin-track railway line "Koralmbahn" later this year. The test dome, which will afterwards serve as an event canopy, has a length of 26,5 m, a width of 19,1 m and a height of 4,2 m. Its transformation process was successfully completed, its weight of 80 t being lifted with only 20-22 millibar from the flat plate to the spatially curved shell. "We could improve the construction method once again decisively during the preparation of the project for this first application," explains Dr. Benjamin Kromoser. In summer 2017, the final building will be ready for use, and till then, an additional concrete layer will be applied and some areas will be cut away.
Initially flat slab before inflation
Finished concrete shell after the transformation process
Prepared concrete shell for the application of an additional concrete layer
Geometry optimized dome and unrolled initially flat slab before inflation (Geometry optimization DI Thomas Pachner
Visualization of the finished event canopy with view from outside
Visualization of the finished event canopy with view from inside
Source: Vienna University of Technology