SAFETY APPRAISAL OF SUSPENSION BRIDGE MAIN CABLES. CONTRACTOR'S REPORT FROM A WORKSHOP IN NEWARK, NEW JERSEY, NOVEMBER 16-17, 1998

Suspension bridges in the United States have cables that range in diameter up to 36 in. (91 cm) and consist of up to about 28,000 individual wires each. Some are constructed of pre-formed structural strands, but the majority are spun-in-place from individual wires laid parallel. The large number of wires in a parallel wire cable is both an advantage and a disadvantage. It is an advantage in that it provides significant internal redundancy to the structural system, allowing repair or replacement of individual damaged wires. It is a disadvantage in that it is very difficult and costly to determine the extent of deterioration occurring within the cable that could affect its load carrying capability. Guidelines and techniques to determine the significance of the various numbers of internal cable wires with various levels of deterioration are lacking. Defining the scope of the problem and the research needs to address the problem were the goals of this Workshop. The participants in the Workshop developed a list of research needs for providing improved nondestructive inspection and evaluation techniques. 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. The research should provide owners with more reliable information on the actual condition and strength of the key members of their suspension bridges -- the main cables; and with useful information on cable maintenance and rehabilitation procedures.