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SPEAKERS:                   BERNARD ESPION                       

DATE & TIME:                5.45PM FOR 6.15PM ON MONDAY 7TH APRIL


PLACE:                           THE GALLERY, 77 COWCROSS STREET, LONDON EC1M 6EL


The early history of prestressed concrete in Belgium is invariably associated with the name of Gustave Magnel (1889-1955), professor at Ghent University, who began experimenting with prestressed concrete in 1941. He is often credited to having developed a system of post-tensioning consisting of anchorage with flat wedges and tendons known as « Sandwich » or « Blaton-Magnel » which was widely used in Belgium, and also a bit in the UK, after the second World War and up to the beginning of the 1960's.

Up to now, the written sources for studying the history of the early development of prestressed concrete in Belgium were Magnel's publications. However they do not mention the origins and the dates of the first prestressed concrete structures in Belgium. Very recently, the archives of the contractor Blaton have surfaced. This contractor, who patented the "Sandwich" system in March 1942, was also responsible for most of the first and important applications of prestressed concrete in Belgium in the 1940's and early 1950's. These archives provide a new commentary on the early days of prestressed concrete in Belgium. They clearly show the involvement of the contractor Blaton in the industrial development of the system, the promotion of use with many unrealized projects and the interactions between Magnel and Blaton.

Magnel, who had worked in London with the contractor Somerville during the WW1 was fluent in English, and his textbook on Prestressed Concrete, published in French in 1948, was translated into English and published in the "Concrete Publication" series the same year. Being the first of its kind and also very good, it soon became a standard reference worldwide.

Besides early applications (1942-1950) of the Sandwich system, another Belgian innovation in prestressed concrete of that period will be described - the external post-tensioning with 40mm diameter high strength steel bars tensioned at 700 MPa applied to a 44.5m span footbridge - , designed in 1943 but not built till 1947 - well before the first application of Dywidag bars in Germany.

Do come and hear about a hitherto unknown aspect of the early history of prestressed concrete by Professor Bernard Espion - Director of the Laboratory for Testing Materials and Structures at the University of Brussels.