Field Testing and Performance Evaluation of a Through-Plate Girder Railway Bridge

The performance and behavioral characteristics of an old through-plate girder railway bridge are presented. Strain gauge instrumentation was used to monitor structural responses under current operating conditions. Loading spectra of crossing trains were measured with a train weighing system and used as applied loads in subsequent finite element models. The experimental and analytical results indicated that the stress responses of the bridge structure were controlled mainly by axle loads and axle spacings. A certain degree of continuity was observed at the stringer-to-floor-beam connections. Consequently, the typical assumption of simple shear connection could give unrealistic estimates of stress responses in the stringers. The structural responses in floor beams and plate girders were, however, less sensitive to the degree of continuity at the connections. On the basis of Miner's hypothesis, the fatigue damage accumulation and the equivalent number of stress cycles in main bridge members were evaluated. Although freight trains had greater axle loads, the fatigue damage was dominated by passenger trains because of their large number of stress cycles. The equivalent number of cycles per train crossing was found to be considerably less than the value provided in the Manual for Railway Engineering of the American Railway Engineering and Maintenance-of-Way Association. The findings provided favorable information for the performance and fatigue evaluations. The structure was shown to have an adequate capacity for current operating conditions. In addition, use of the research results would provide a more accurate estimate of the fatigue life.