According to Polish Standard PN-82/S-10052 special quality joints assigned to defectiveness class R1 or R2 are allowed in new bridge structures; usual quality joints on the other hand should have the quality not inferior to class R3 joints. No physical state of deterioration whatsoever is allowed in structures. These requirements are not satisfied in case of structures in operation. For example in 9 welded bridges built in the years 1935-1939, presented in this paper, underbead cracks have been found in 88.9% of butt joints on examined structures and joints of R4 and R5 defectiveness class were present on all objects. In order to determine the further safe period of utilization of these bridges, fatigue strength investigation of welded butt joints in these structures was carried out and stress analysis made.
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