The Parallel-Wire Strand System for Suspension Bridges

Invented by Jackson L. Durkee, Class of 1943

As a structural engineer in the Fabricated Steel Construction Division of Bethlehem Steel Corp., and later the company's chief bridge engineer, Durkee developed a host of innovations that changed the way long-span bridges are built. He was also directly involved in the design and construction of numerous bridge projects, including the second Tacoma Narrows span in Washington and the Walt Whitman Bridge in Philadelphia. He now confers on international bridge projects as a consulting structural engineer.

His best-known innovation is the parallel-wire strand system for constructing suspension bridge cables. He first thought of the concept while standing atop a bridge tower in 1959. He later determined that by making the strands in bridge cables parallel, instead of twisting them into a helical configuration, the cables could support considerably more weight with less mass. The revolutionary technique also eliminated the need for the "aerial spinning" method of cable construction that had been invented 125 years earlier by John Roebling, designer of the Brooklyn Bridge.

The parallel-strand wire technique was used for the first time during the construction of the Newport (R.I.) Bridge in the late 1960s and has since been employed on bridges all around the world. For his accomplishments in bridge design and structural engineering, Durkee has won the Ernest E. Howard Award (known as the structural engineering gold medal) from the American Society for Civil Engineers, which has also elected him a fellow and an honorary member. He was elected to the National Academy of Engineering in 1995.

 
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