Fatigue life of riveted bridges: Fid-Bau Portal

Fatigue life of riveted bridges

Kulak, G.L. / Adamson, D.E. / DiBattista, J.D.

Many old riveted bridges have now endured millions of cycles of stress, and often it is essential that they remain in service. The effects of fatigue damage in these structures must be considered in order to make their continued safe use possible. However, despite the large number of riveted bridges still in service, only a limited amount of research has been carried out on riveted connections as compared to research on welded or bolted connections. Furthermore, these structures generally carry greater loads and a higher frequency of traffic than contemplated in their original design. More information about the actual fatigue life of such structures is required. Determination of fatigue life requires knowledge of the past loading history of the structure and prediction of its future loading, determination of a suitable fatigue category for riveted details, and calculation of the stress range at the detail. The results of physical tests carried out on members taken from a railway bridge removed from service are reported in this paper. These are combined with test results obtained by others in order to make a recommendation for the detail fatigue category. Measurements made on the bridge before it was dismantled also permit recommendations to be made regarding the level of the structural analysis necessary for calculation of the stress ranges. Two types of members were taken from a case study bridge for physical testing. These were the floor system stringers and the tension diagonals. In the case of the stringers, the critical section for fatigue was either at the location where rivets fastened the flange angles to the web or where rivets fastened a lateral bracing gusset plate to the flange. The tension diagonals were removed from the structure with the panel point gusset plates intact. The critical detail was the riveted connection of the gusset plate to the flange angles that were part of the built-up cross-section of the main member. The results of the physical tests, taken in combination with similar tests by others, enable a fatigue category for riveted connections to be selected. This is then used in conjunction with the case study bridge to predict its remaining fatigue life.