Fatigue safety verification of a steel railway bridge using short term monitoring data

The case study of the fatigue safety examination of the 120 years old steel riveted bridge carrying a single railway track on two main girders is presented. The overall assessment according to the Swiss Standard SIA 269 for existing structures indicated sufficient resistance at Ultimate Limit State but not at Fatigue Limit State, and the replacement of girders was recommended. To challenge this, the detailed examination was performed using data obtained from short term monitoring by the system installed on the main girders of one span over a period of four weeks. Fatigue stress histograms were constructed, and it was shown that measured stress ranges are smaller than the fatigue endurance limit, indicating a theoretically infinite fatigue life. No structural intervention is thus necessary. This case study shows that a simple short term monitoring is very useful for the fatigue examination of bridges allowing for reducing or avoiding (costly) interventions on structures.