Many steel bridges constructed before 1970 are now of concern because they contain welded fabrication details that are highly susceptible to the formation of fatigue cracks. It is imperative that nondestructive evaluation methodology be available to examine such bridges, especially those with more than 25 years of service history and high volumes of truck traffic. Within ohio a large number of bridgeswere fabricated with welded splices and cover plates located over the piers of continuous-beam bridges. Commonly accepted analytical models indicate that the average fatigue life has already been exceeded in some situations. Unfortunately, unaided visual inspection allows no opportunity for early crack detection because the critical top flange surface is embedded in the concrete deck. Research conducted on behalf of the ohio department of transportation has demonstrated that ultrasonic testing procedures may be used to determine whether cracks have been initiated within a top flange surface that is embedded in concrete. Three interstate highway bridges experiencing high volumes of truck traffic and containing aashto category e' cover plate details were examined during 1989. Application of the ultrasound technology is described and the results of this field investigation are presented. This paper appears in transportation research record no. 1275, Bridge research 1990.
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