ENDURANCE MATTERS: DIAGNOSING AND MITIGATING CABLE FAILURE

During construction of 1,100-foot-long twin steel arch bridges, three of the vertical hanger cable anchorages fractured in fatigue within weeks of installation. The failures were attributed to wind-induced vibration of the cables under low wind speeds. Dampers were installed to reduce the vibrations, but concern remained over the continued cable vibrations. Pivot was engaged to evaluate the long-term reliability of the cable anchorages.

Pivot performed field testing and monitoring to assess the ongoing cable vibrations and their impact on the cable anchorages. Based on analysis of the field data, Pivot determined that the risk of more cable anchorage failures within the bridge service life was higher than that allowed by bridge design codes. 

Pivot recommended solutions to strengthen the cable anchorages to reduce the risk of failure to an industry-acceptable level. The bridges were repaired and safely opened for use.