French civil engineer who successfully developed pre-stressed concrete—i.e., concrete beams or girders in which steel wire is embedded under tension, greatly strengthening the concrete member.

Appointed bridge and highway engineer at Moulins in 1905, Freyssinet designed and built many reinforced-concrete bridges, including one with a 300-foot (91-metre) span. From the end of World War I until 1928 he worked for a contracting firm, and in 1930 he completed the Plougastel Bridge across the Elorn River at Brest. With three 612-foot (187-metre) spans, this was the largest reinforced-concrete bridge constructed up to that time.

After 1928 Freyssinet devoted himself to the development of pre-stressed concrete and also to the manufacture of high-strength concrete. His most significant discovery was that only a high-strength steel at a high stress would achieve a permanent pre-stress in concrete. At first little recognized, Freyssinet's methods were successfully applied at the Gare Maritime (harbour station) at Le Havre, Fr., in 1933 and gradually became universally adopted. After his invention in 1938 of a practical tool for applying tension to steel, the use of pre-stressed concrete became worldwide.