The failure of metal bridges, subject to in-service fracture problems mainly caused by fatigue, may be prevented or minimized by performance of periodic nondestructive testing. Attendant factors that justify funding for such inspections include the potential for bridge failure, the consequences of bridge collapse, risk analyses, and inspection strategies. Factors that affect structural integrity include structural design, construction quality, and service loadings.

Details of a computer/strain-gage system capable of obtaining strain-gage data from critical structural elements are described. Data are processed to determine the stress-range distribution, number of stress cycles, resolved mean stress range, need for structural inspection, critical crack size, suitability of the inspection method, and required inspection interval.

Factors relating nondestructive test methods to periodic inspections are presented. The application of a functional acoustic-emission system suitable for bridge nondestructive inspection of bridges are described. Optimum test methods for conventional and cable bridges are presented.

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Prepared for presentation to 2nd International Conference: Structural Failure, Product Liability and Technical Insurance (Vienna, Austria: July 1–3, 1986).