Cracking and Fracture of Suspension Bridge Wire

Abstract

When water enters a suspension bridge cable, the wires that make up the cable start to deteriorate. The protective zinc coating is the first element that is damaged, followed by corrosion of the steel itself. The wires are subjected to high axial tensile stresses from the bridge loading, bending stresses caused by straightening the curved wires inside the cable, and residual stresses introduced in their manufacture. These stresses, along with the corrosive environment, can lead to stress corrosion cracking or hydrogen-assisted cracking, two processes that lead to eventual failure of the wires. A fracture analysis indicates that the wires in the cable may be subjected to slightly different forces than a wire tested in the laboratory, but that the results of laboratory tests will give conservative values of cable strength.