Concrete Shell Fabricated with "Pneumatic Wedge Method" in Vienna, Austria
Vienna University of Technology (TU Wien)
Institute of Structural Engineering
Concrete construction E212-2
The "Pneumatic Wedge Method" is a new technique for the construction of double-curved concrete surfaces by means of pneumatic formwork. The advantage of this method is that elaborate structures for molds and scaffolding are not needed anymore.
Using the "Pneumatic Wedge Method", the Vienna University of Technology has built a double-curved concrete shell as part of a research project. The deformation process and the final structural conditions have been checked with RFEM.
Pneumatic Wedge Method
The fabrication of the multi‑curved shell starts from a flat position. There, a round concrete slab with wedge-shaped cutouts is created. In addition, inflatable air cushions are arranged under the slab and the wedge-shaped gaps.
At the slab's circumference, unbonded tendons are installed which are stressed on two opposing stress locations. At the same time, the air cushion placed below the shell is inflated. Along with the inflation, the wedge-shaped air cushions are compressed. The circumference of the concrete slab is being reduced, the slab is being arched upward and forms a double-curved shell.
The purpose of the pneumatic wedges is to stabilize the structure during the forming process. After the completion of the shell, it is possible to reuse them.
In the experiment of the Vienna University of Technology, the shell was deflected to the intended height of 3.5 m. Then, the tensioning cables (strands) were fastened on the anchor blocks and the joints between the elements were filled.
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Programs Used for Structural Analysis
Structural engineering software for finite element analysis (FEA) of planar and spatial structural systems consisting of plates, walls, shells, members (beams), solids and contact elements