Efficient construction of concrete shells by Pneumatic Forming of Hardened Concrete: Construction of a concrete shell bridge in Austria by inflation

摘要

Concrete shells are very efficient structures, spanning wide areas with very little construction material. Unfortunately the formwork needed to erect concrete shells is still very labor and material intensive. An alternative construction method which is more time and resource friendly is Pneumatic Forming of Hardened Concrete. A simple air cushion in combination with additional post-tensioning tendons are used to transform a flat concrete plate into a double curved shell. This paper describes the design and construction of the first practical large-scale application of this building method for the construction of the deer pass "AM 2" over the newly built two-track rail Koralmbahn in Carinthia in the south of Austria. The plan measurements of the bridge are 36.2m by 38.7m with the height of the shell from the top edge of the foundations to the vertex mounting to 7.6m. Within the construction process a flat 100mm thick hardened concrete plate with a weight of 546t was lifted to the designed double curved shell. This thin concrete shell served as lost formwork for the final bridge.