Dynamic Amplification Factor Variation Analysis of a High-Speed Railway Bridge under Multiple Loading Cases

Long-span and wide railway bridges are loaded with various loading cases, and the structural dynamic amplification factor (DAF) corresponding to different loading cases has great variability. This study presents an approach to obtaining DAF under different loading cases. Then the approach is applied to the analyses of DAFs from long-term monitoring data. The usual values of vibration amplitude and DAF under eight single-train loading cases during long-term operation are analyzed, and the midspan amplitude and displacement DAF of the main girder under the typical two-vehicle intersection, three-train intersection, and four-train intersection loading cases are also investigated. The correlation between the DAF of the eight loading cases, the structural temperature, and the train speed under the single-train loading case is analyzed. The obtained results show that in the long-term operation, the vibration amplitude level and DAF level of the railway bridge are mainly related to the train loading case, and in 16-carriage loading cases, the DAF value is higher than that in eight-carriage loading cases in the same line. The vertical dynamic response of the midspan main girder under each working condition is small. Furthermore, depending on this evolution law, different traffic loading cases must be considered during the assessment of dynamic performance.