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T. Pachner, B. Kromoser, J. Kollegger:
"Structural Optimization of a concrete shell bridge with the Pneumatic Forming of Hardened Concrete construction method";
Talk: IASS 2016 International Symposium, Tokyo; 2016-09-26 - 2016-09-30; in: "Proceedings of the IASS Annual Symposium 2016 "Spatial Structures in the 21st Century"", (2016), 1 - 10.

Concrete shells designed according to the flow of forces are very efficient structures. The construction material concrete has a comparatively high compressive strength and a low tensile strength. If a shell design is harmonized with the material properties 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 structure.
The basic problem is that the costs for formwork and falsework have made these fascinating structures less and less economical to build. Thus, the construction of shells decreased over the years, and hardly any shells have been built in the last 30 years.
A new construction technology called Pneumatic Forming of Hardened Concrete (PFHC) was invented at the TU Vienna managing the construction process completely without formwork and falsework [1], [2], [3], [4]. A pneumatic formwork lifts a flat hardened concrete plate and at the same time additional post-tensioning cables are tightened to support the bending process of the flat plate into a semi-discrete surface resembling a double curved shell. The functionality of the construction method was successfully tested in two different large-scale experiments.
A very challenging task is to design a concrete shell according to the impacting forces and to the boundary conditions needed for PFHC. In the present paper the geometry optimization for the construction of a deer pass over a two-track rail will be explained.

form finding, optimization, concrete shells, membrane structures, flat starting plate