Philadelphia Bridge Sparked Growth of Prestressed Concrete in the U.S.

Prestressing has been used for centuries. For instance, iron bands were heat-shrunk over built-up wooden wheels to increase their resistance to damage. In 1888, a man named Jackson from San Francisco first applied controlled stresses to concrete by tensioning steel rods. Since engineers of those days were unaware of the plastic strain of both steel and concrete, Jackson’s prestressing soon disappeared. Ultimately, commercial prestressed concrete came about only after development of high-yield-strength prestressing steel and high-strength concrete. As the 20th century wore on, prestressing grew, then was interrupted by World War II. The war over, most bridges over the Rhine and other major rivers in Europe lay in ruins. Further, there was a great shortage of steel productive capacity. Thus, a great impetus to innovative use of prestressed concrete for long-span bridges throughout Europe. In 1949, Philadelphia built the first major prestressed concrete bridge in the U.S. This greatly impressed American engineers, spurring the growth of prestressed concrete both in bridges and buildings.