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B. Kromoser, J. Kollegger:
"Building concrete shells without formwork and falsework";
Talk: fib Symposium 2016, Cape Town; 11-21-2016 - 11-23-2016; in: "Performance-based approaches for concrete structures", (2016), ISBN: 978-2-88394-120-5; 1 - 8.

Concrete shells are very efficient supporting structures. They the can span very large areas with very small thickness and without requiring any columns. If the form of the shell is chosen correctly, the applied loads induce mainly compressive normal forces in the shell, which leads to a very uniform and efficient distribution of the stresses in the entire concrete structure. Barriers for the widespread use of shells are the high effort for the production of the complicated formwork and the needed supporting falsework. A new construction method called "Pneumatic Forming of Hardened Concrete (PFHC)" was invented at the Institute for Structural Engineering at Vienna University of Technology. Starting from a flat hardened concrete plate a double curved concrete shell is built with the aid of a pneumatic lifting structure. The transformation process is additionally supported by pre-tensioning strands at the circumference of the concrete plate. During the transformation process the petal shaped elements are bent. Using steel ropes as reinforcement allows for large strains in the tensile loaded areas and ensure a smooth curvature of the single curved elements. Two large scale experiments were already performed in Austria to prove the practical applicability of the new construction method. This paper will describe the functioning of the new shell construction method, preliminary bending experiments, the two large scale experiments and possible practical applications.

concrete shell, pneumatic formwork, active bending, flat starting position, pneumatic wedge.