Guidelines for Inspection and Strength Evaluation of Suspension Bridge Parallel Wire Cables

摘要

There are nearly 50 major suspension bridges in the United States, and more than half of them are more than 50 years old. These bridges represent major investments and are essential transportation links for regional and national commerce and lifelines. As this group of major structures advances in age, the number of in-depth evaluations to determine their condition and load-carrying capacity is expected to increase. The need to estimate remaining service life and to take preventative steps to extend service life will also increase. There has been no reliable and nationally recognized procedure, either practical or theoretical, to inspect and evaluate the condition and strength of suspension bridge parallel-wire cables. At the NCHRP-sponsored Workshop on Safety Appraisal of Suspension Bridge Main Cables held in Newark, New Jersey, in 1998, the highest priority research needs identified were (1) development of cable inspection, sampling, and testing guidelines and (2) development of models to predict the strength of deteriorated cables. Unreliable methods of inspection and evaluation could result in unnecessary replacement or in unexpected failures. The objective of this research was to develop the needed guidelines for inspection and evaluation of suspension bridge parallel-wire cables. These guidelines provide details of the cable inspection process, including wire sampling and testing. Complete instructions, illustrated with examples, are provided for using the condition and properties of the cable wire, determined by inspection and subsequent laboratory testing, for estimating cable strength. An accompanying CD-ROM (CRP-CD-54) contains a full account of the research leading to the development of the recommended guidelines and provides derivations of all equations.