An Investigation on the Interactions Between High Speed Trains and Simple Span Precast Concrete Bridges

Dynamic response of railway bridges during the passage of high speed trains depends on several parameters, e.g dynamic properties of bridge and train, pavement type and train speed. This paper presents the results of a research in which the impacts of these parameters were investigated on four simple span bridges with the 10, 15, 20 and 30m span lengths and under train speed at the range of 100-450 km/h. The first three bridges were designed in accordance to the guidelines of Iranian Management and Planning Organization. The forth bridge, was designed as a prestressed concrete bridge. To evaluate the dynamic response of bridges, two different models of the bridge and vehicle were chosen: one considering the interaction between bridge and vehicle over flexible pavements (ballast) and the other by modeling the train as a series of moving loads without considering the pavement effect. The measures that were considered for comparisons were: resonance and cancellation speeds, the impacts of stiffness variation on them, and the influence of the number of coaches. The results indicated that the acceleration magnitude in the middle of 10,15 and 20 m span bridges were lower than the 30m prestressed concrete bridge which may be attributed to their lower weight. The results indicated that whilst the resonance speed obtained via moving loads modeling was somewhat higher than other modeling methods, the bridges response in resonance conditions was conservative. During the bridge operation, as the time goes by, the changes in the mass and stiffness of the bridges cause the resonance occur at slower speeds. The results also indicated that the number of coaches would only affect on the main resonance speed.