1950 - 1960: The silos continue their triumphal march 

In 1953, the firm presents the world's prestressed concrete silo constructed using the slip form method. Designed to hold 17,000 tonnes of white sugar and built in Odense, Denmark, this is to be the first of many Ostenfeld silos built over the next 20 years…
The Ostenfeld silo sets itself apart from other silos in that its walls, despite the silo's huge dimensions, are just 25cm thick – a significant difference in terms of costs. Being prestressed, the walls can bear the pressure from within and remain totally sealed.

By drawing on hygrometry (the study of the humidity of air and other gases), Ostenfeld & Jønson is able to design silos with what at the time are seen as highly advanced fully automated control systems to ensure the precious sugar content will not form into crystals, as is the tendency when stored in other types of silo.
Photo: COWI

The orders come flooding in

Prestressed concrete is also proving to be a success in other areas. The duo of Ostenfeld & Jønson and their by now 50-strong staff are Scandinavia's undisputed favourite consulting firm in the construction field.

And as the Scandinavian leader where prestressed concrete is concerned, the firm is awarded contracts for multi-level tram depots, railway tunnels beneath seven-storey houses, concrete tanks for boiling laundry water, and countless swimming baths.

In 1953, a quarter of the firm's turnover is generated outside Denmark, and in 1956 an office is opened in Paris, followed three years later by one in Ghana.

Exporting ideas

The firm is awarded its first silo contract outside Denmark in 1954 when a French sugar factory in Eppeville places an order for a silo constructed according to the established Weibull method. Ostenfeld & Jønson design the structure and oversee the construction of the prestressed concrete walls. This is the first time prestressed concrete is exported back to France, its country of origin.

Five years later, the first Ostenfeld method silo is built: a 13,000 tonne silo for the Beghin sugar company's factory in Lieusaint just outside Paris. Many in the sugar industry are attracted to the Ostenfeld model, and the market booms.

Over the next 15 years, the firm designs 80 silos for companies across Europe.

Complex construction project

Alongside their work with prestressed concrete, Ostenfeld & Jønson design their largest building so far: the Copenhagen county hospital in Glostrup, constructed during the period 1951-1958. The hospital has a total gross floor area of 80,000sq.m and a subterranean tunnel system.

In an unprecedented move, the hospital's work routines, treatment options and operating efficiency are all taken into consideration in the planning of the load-bearing structures.

All this during a period when medical science, medical engineering and technical engineering are undergoing rapid development.

It becomes clear that designing a hospital is the ultimate test of a consulting engineers' expertise in the field of construction.

Bridge building continues

The firm continues to design bridges and tunnels in Scandinavia including the High Bridge in Fredrikstad, Norway, crossing the Glomma River, the Egernsund Bridge in the south of Jutland and the Virksund Bridge south of the Limford, both in Denmark, the pedestrian bridge at Mykines in the Faroe Islands, and the prestressed immersed tunnel at Liljeholmsviken in Sweden.