Publication: Construction method to build ice shells with pneumatic formwork
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2010-02
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2010
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Abstract
This thesis has presented a study into the new construction method to build ice shells with pneumatic formwork, developed at the Institute for Structural Engineering of the Vienna University of Technology. Shells are natural, logical and functional load carrying systems. Additionally, for the load transfer of a uniformly distributed load, the shell structure is the perfect choice because mainly normal forces appear in the cross section. Although shell structures possess excellent load carrying system and make a great visual impact, only few shells have been built in the last decades. The main problem is the difficult, time-consuming and expensive production. Traditionally, shells are produced by means of complex formwork. Creating such formwork increases the construction time and affords additional material which cannot be reused after the shell has been completed. Ice as a construction material is either used as a decorative material on a supporting structure or it is applied in structures with very low stress states due to self weight and wind forces. Ice shells can be used in temporary architecture, as roof structures for sport and music events, or presentations and promotions of sale products. Moreover the translucent nature of ice, allows several possibilities to make attractive this structure. For instance the internal illumination of the ice shell during the night creates a luminous atmosphere in the surroundings. The new construction method consists of transforming an ice plate into an ice shell by means of a pneumatic formwork. The ice elements, with steel tendons inside, are cut form an initial ice plate. While air is inflating the pneumatic formwork the elements creep. When the pneumatic formwork is removed chains support the stress of each element. Afterwards a pull-chain system is used to lift the elements from the top of a wooden tower built at the centre. The elements are linked and we retire the tower and the chains, the ice shell is finished. Before building the ice shell in Obergurgl, Tyrol (Austria) we tested different experiments making ice beams in a temperature-controlled container in Vienna. Moreover we used finite element software, RFEM4, to study and to compare the load configuration with the analytical solution. In Obergurgl the ice elements were creeping but we could not lift the elements into an ice shell. The night before lifting the pneumatic formwork had an air leak and the most of the elements were broken. But the problem was that the chains under the pneumatic formwork did not work rightly so the chains did not support the stress of the ice elements. Therefore the problem was the design. For further experiments we would change the design with the pneumatic formwork and the chains due to it is not a good solution. As many engineering experiments at this time did not end well but these construction method is in development and it has real possibilities nowadays in the market. Moreover with the work team at the Institute for Structural Engineering of the Vienna University of Technology they can get substantial progress in the construction field.
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Cálculo de estructuras, Elementos de la construcción, Cúpulas de hielo, Ensayo de materiales, Mecánica de sólidos