Prestressed concrete General – Materials – Prestressing losses

While the origins of many techniques are often uncertain and controversial, the invention of prestressed concrete is unambiguously known, since only one man, Eugène Freyssinet, can legitimately lay claim to it. It was he who, in 1908, designed and built the tie rod for the Le Veurdre test arch, the indisputable ancestor of all prestressed concrete structures, which was lost during the First World War and then found by chance in 1991 in a private garden near Moulins. It was he who, in 1928, registered the first patents on anchoring by adhesion, at the origin of prestressing by pre-tensioning, then who, within the forclum company, developed all the techniques enabling its effective implementation (structure of molds, pre-stretching of wires, dewatering and steaming of concretes...) for the production of electricity poles. He also invented the first operational post-tensioning anchoring system and associated jack (patented in 1939)...

Although Eugène Freyssinet was a remarkable builder, a pioneer with a vivid imagination, a remarkable experimenter and observer, a hard-working and demanding man, he never devoted much time to publishing his ideas or, above all, to popularizing them by structuring and detailing them in such a way as to facilitate their appropriation by as many people as possible. It is to the credit of a few of his close collaborators, including Yves Guyon and Pierre Lebelle, that he made all these new concepts accessible to the engineering community, founded a coherent theory and developed simple rules for pre-dimensioning.

The present article and the [C 2 377] article are modestly in line with this approach. Their scope is limited to the prestressing by tendons of concrete structures essentially made up of beams. It focuses on the dimensioning and constructive provisions of these structures. Information on implementation methods and techniques is given insofar as it is useful for calculation and detailed design.

Since the work of Guyon and Lebelle, design principles and methods have remained unchanged. On the other hand, materials, both steel and concrete, have progressed considerably, as can be seen from the French and European standards that apply to them. Calculation and justification rules have also undergone significant changes, with the French rules giving way to the Eurocodes. This article covers the latest developments in these standards, and in particular in Eurocode 2, which deals with design rules and constructive provisions for concrete constructions.

After showing how to prestress a structure and evaluate its effects (§