INVESTIGATION ON TENSILE STRENGTH AND CORROSION OF SUSPENSION BRIDGE HANGER ROPES USED FOR 77 YEARS

The hanger rope used for 77 years on the Bear Mountain Bridge, USA, was removed from the bridge and its tensile strength and corrosion condition were investigated. The specimens made from the removed hanger rope had almost the same tensile strength as that of the virgin rope. There observed some steel corrosion on the outer strands, but the center strand was lightly corroded with no steel rust. The corrosion mechanism is estimated as follows; water intrudes through the cracked paint and it stays inside of the rope, which makes the rope inside very humid and corrosive. The Bear Mountain Bridge is situated in countryside with relatively dry and low temperature. This mild climate keeps the inside of the rope dry and prevents the corrosion acceleration of the hanger ropes.