AbstractAlthough many riveted bridge structures made of old structural steel from the 19th and early 20th centuries are still in use today, there is usually no need to replace them. When assessing these steel structures with regard to necessary refurbishment or strengthening measures, engineers need information about the remaining fatigue lifetime in particular.Often no sufficient remaining fatigue life can be determined based on normative S‐N‐curve assessment. An initiation of fatigue cracks has to be assumed. These cracks occur primarily at the edge of the rivet holes. In the early phase of crack growth below the rivet head, the crack cannot be found in a visual inspection of the structure. For this reason, the remaining cyclic lifetime based on fracture mechanics is determined assuming a start length of the crack beyond the rivet head.This paper reports investigations using phased array ultrasonic testing as a NDT method for detection of hidden cracks in riveted joints. The results have shown that cracks below rivet heads can be detected. The detectable crack length depends mainly on the space available at the test position, the condition of the corrosion protection coating, and, last but not least, the quality of the old structural steel.
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