ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.
Issue link: http://www.aspiremagazinebyengineers.com/i/319569
12 | ASPIRE, Fall 2010 P E R S P E C T I V E Eugène Freyssinet has been proclaimed one of the most complete engineers of the twentieth century and one of the greatest builders in history. Yet his story is not well known because he was intensely modest and private, and did not write about his work. Only three books have been written about his life and work. Freyssinet often stated, "I was born a builder." He would go on to build five world-record span length bridges, in addition to being the acknowledged inventor of "prestressed concrete" i n c l u d i n g p r e t e n s i o n i n g , t h e development and use of flat jacks, and post-tensioning. Freyssinet was born in the countryside near Objat in 1879 and started his career in 1905 in Moulins. He built n u m e ro u s b r i d g e s i n t h e re g i o n , including the Praireal-sur-Besbre Bridge in 1907, a three-hinged arch having a span length of 85 ft. This was the first bridge in the world to have the formwork of the arch removed by creating forces using jacks at the crown hinge. World-record span Length Arch Bridges Freyssinet and the contractor Mercier Limousin designed and built concrete arch bridges, which successively broke his own world record for span length. They are : • 1912, Veurdre Bridge (238-ft span) • 1920, Villeneuve-sur-Lot Bridge (315- ft span) • 1923, Saint-Pierre-du-Vauvray Bridge (430-ft span) • 1930, Plougastel Bridge (610-ft span) The main problem during construction o f t h e Ve u r d r e B r i d g e w a s t h e decentering of the three large arches that were subjected to creep and shrinkage. This was mitigated by using jacking thrusts following the procedure first used on the Praireal-sur-Besbre Bridge. The initial bliss after construction was complete was soon followed by dreadful agony as disconcerting deformations (due to creep and shrinkage) started appearing, first slowly and then more rapidly until there was no possible o u t c o m e i m a g i n a b l e o t h e r t h a n collapse. Freyssinet took four reliable men, placed the decentering jacks back in the crown hinge, and began to raise all three arches at once, until the bridge regained its original shape. On future bridges, he eliminated the crown hinge and continued to study the problem of "deferred deformation," a phenomenon that the administrative authorities obstinately denied the existence of, and the official laboratories neglected or refused to measure over sufficiently long periods of time. Invention of prestressed concrete In 1928, Freyssinet patented the first of his three inventions for applying compression to concrete by "pre- tension and bonded wires," which was the birth of prestressing. His other two methods were his 1938 invention of by Ken Shushkewich, KSI Bridge Engineers The Story of Eugène Freyssinet World-record span length arch bridges designed by Eugène Freyssinet. Eugène Freyssinet. ASP10-1704.indb 12 9/17/10 2:05 PM