Mechanical Properties and Remaining Strength of Corroded Bridge Wires

Corroded galvanized steel wires at different corrosion levels were produced, and their mechanical properties and remaining strength were investigated. It was found that the actual tensile strength of corroded wires does not decrease, whereas the elongation, torsional and fatigue strength decrease sharply. The amount of hydrogen absorbed in the corroded wires was measured, showing that it did not reach the level to cause hydrogen embrittlement. The surface of corroded wires is uneven and this s urface roughness seems to decrease ductility of corroded wires. Broken wires cut from an old suspension bridge were also investigated. The fracture surface is similar to that caused by corrosion fatigue rather than by hydrogen embrittlement. It is estimated that the wires were fractured by the mixed effects of corrosion, cyclic stresses, high residual stresses, hydrogen and fretting.