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In 1946, Wriborg W. Jønson becomes a full partner and the resulting partnership is christened "Chr. Ostenfeld & W. Jønson, Rådgivende Ingeniører" (in short, Ostenfeld & Jønson).The staff now numbers 25, many of whom are soon to receive further in-house training. Ostenfeld decides that any employees who are not directly involved in ongoing projects are to undertake further studies and training in an effort to create experts in the technique and theory of prestressed concrete.
The concrete used for construction at this time is not very durable, and it is impossible to find the space required for the necessary reinforcement of long beams if the desired result is to be a slim, light structure with good casting qualities.
Ostenfeld believes that prestressed concrete is the way ahead. And if you want to be the best, you have to learn from the best. So he sends an engineer to the Mecca of prestressed concrete, the Société Technique pour l'Utilisation de la Precontrainte, in Paris, which is led by the father of prestressed concrete, Eugène Freyssinet.The engineer comes back laden with paradigm plans which the firm further develops and adapts to the Danish climate with its periods of frost and thaw – factors that have not been taken into account by the French engineers.
Chr. Ostenfeld & W. Jønson, Rådgivende Ingeniører does its best to inspire the Danish construction industry to invest in the latest technology so that prestressed concrete innovations can be put into practical use. While the French are creating huge, load-bearing concrete structures with spans that were previously only possible using steel, Ostenfeld has decided to take the new technology one step further and has designed a cylindrical tank for liquids and granulated materials.Here, the prestressing concept comes into its own, almost completely eliminating any upper limits on the possible dimensions of such tanks. This groundbreaking development of prestressed concrete secures the firm a leading international position in the area over the next ten years, with its know-how even being re-exported back to France.
Ostenfeld's first prestressed concrete tank, designed to hold 1,000 cubic metres of fuel oil, is constructed at Kalundborg Harbour in Denmark. Prestressing cables have been cast into the wall of the tank. This is the first example of what is later to become the world renowned "Ostenfeld silo".In addition to large-diameter tanks for water, oil and sugar, the firm mainly designs prestressed concrete bridge structures.
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