Phase I Inspection of the Stay Cable System on the US 231 William H. Natcher Bridge over the Ohio River

Abstract

The US 231 Natcher Bridge was opened in 2002. By 2006 cracking was observed in the plastic piping that protected the stay cable strands from the environment at both the deck and tower anchorages. Over time the extent of cracking increased and an investigation was initiated to assess the types of deterioration impacting the cables, their causes and their impacts on the integrity of the stay cables. From 2012-2015, a series of in-depth field inspections were performed using visual and nondestructive testing. Most of this work focused on the piping at the deck anchorages. The inspections disclosed voids in cable grouting, bad welds in the plastic piping and deterioration of the co-extruded outer layer of the piping. Water was detected during inspections of the cable ends at the anchor blocks along with minimal corrosion of the strands and anchorages. The water and samples of the plastic piping were evaluated and found to be problematic. No direct indications of cable corrosion damage were observed, but ultrasonic testing of the strand wires at the deck anchorages revealed possible signs of corrosion. Thermography of the tower anchorages provided extensive grout void indications. Recommendations are provided to address remaining concerns related to the condition of the strands at the towers and to evaluation of strands of selected stay cables at the deck anchorages.