Task 100, FY 1999, "Safety Appraisal of Suspension Bridge Main Cables" (Robert Nickerson). Of the forty-six suspension bridges in the United States with main span exceeding 700 feet, twenty-seven are over 50 years of age and only three are younger than 30 years. Visual inspections of the suspension bridge main cables are very expensive, and physical sampling generally does not provide sufficient data to define the statistical properties of the wires. The objective of this project was to identify issues related to suspension bridge main cable inspection and evaluation and to recommend specific research objectives to resolve these issues.

A list of research needs for providing improved non-destructive inspection and evaluation techniques for suspension bridge main cables was developed at a workshop held November 16-17, 1998. Such research will provide owners with a better definition of what factors affect cable integrity, with improved means of interpretation of inspection results to provide more confidence in cable strength assessment, and with repair or rehabilitation procedures and technology that will extend cable life as much as possible. Successful completion of these projects should provide owners with more reliable information on the actual condition and strength of the suspension bridge main cables and with useful information on cable maintenance and rehabilitation. The final report is available in portable document format (PDF) as NCHRP Web Document 20. (NCHRP Staff: D.B. Beal)