I am unable to pin this down mainly because this is not my field, but the references could help you.

http://books.google.co.uk/books?id=zDnQsoo_uEIC&pg=PA14&lpg=...

1907 Freyssinet aplica el sistema apertura en clave para desencofrar un arco
PRIMER CONGRESO NACIONAL DE PREFABRICACIÓN Realizaciones: Puentes ...
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clave sin hormigonar. -. Colocación de 2 gatos en clave de 1.000 Mp de capacidad y apertura en clave para desencofrar el arco. Gatos de dovela en clave ...
www.pondio.com/sagar.pdf - Similar

Technical English - Spanish Vocabulary
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Arch rib, nervadura de arco. Arch stone, clave, clave del arco de una bóveda. Arch union, unión de arco. Arch wall, arco de refuerzo ...
www.sapiensman.net/.../Technical_vocabulary_Spanish(A22-A).... - Cached

[PDF]
May-June Journal.indb
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els in order to verify for himself this phenomenon of time-dependent defor- ... Freyssinet posi- tioned jacks in the key of the arch, ap- ...
www.pci.org/pdf/publications/journal/2005/.../JL-05-MAY-JUN...

http://www.efreyssinet-association.com/association/documents...

[PDF]
MASONRY DOMES: A STUDY ON PROPORTION AND SIMILARITY
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by H Fernández - 1989
the level of the keystone. The limit slenderness for the first is 1/18.8 .... However, Freyssinet believed firmly on the possibility of erecting .... to remove the keystones and open an 'oculus' without the collapse of the ... at which this occurs depends on the form of the dome and on the system of ...
oa.upm.es/1278/1/PONEN_Huerta_1989_01.pdf - Similar






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Note added at 51 mins (2010-06-13 16:54:35 GMT)
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http://webcache.googleusercontent.com/search?q=cache:I-mkMNe...

by Anonomous User1

Contrary to popular belief, the arch predates Roman times by over a millennium! The Romans, however, are well known for putting this technical innovation to amazing uses. Essentially the arch form transfers loads around openings without compromising the structures integrity of structures.

The arch was invaluable both in projects that we would (today) classify as belonging to the fields of civil engineering and civic architecture. It was vital to the building of bridges because arches allowed water to pass under them while maintaining support to the bridge platform above. In building projects, the arch allowed for a surprising ratio openings-to-wall in tall load-bearing buildings (e.g. the Colosseum in Rome) because of the inherent strength of an arch form.

The amazing rotunda of the Pantheon - arguably the most masterful creation of the Romans - relies on the same basic physical principles as an arch: the load (weight) of the building is passed down continuously from its top to its bottom. However, because it constitutes a full circle they were able to effectively remove what would have been the keystone and create the world-famous oculus (eye) that amazingly opens the top center of the structure to the sky.