Performance of Viaduct Girders Under Static and Dynamic Loads

Full‐scale static and dynamic load tests are conducted for two precast, posttensioned reinforced concrete viaduct girders 22.3 m long. The first girder deflects 19.3 mm at midspan when subjected to a 3,240 kN static load, simulating the superimposed dead load and the RL loading of $\mathrm{BS}5400$ for railway bridges. The second girder is subjected to the dynamic load generated by an empty six‐car train traveling at 30, 60, 70, and 74 km/h. Under the dynamic loads, the midspan strains and deflections are approximately equal to those under the static axle loads. The results show that the longitudinal force transmitted to the piers by an emergency braking is larger than that created by normal traction, the fundamental frequency of the girder is 4.2 Hz, and the forcing frequency of the train is between 0.6 to 1.0 Hz. The frequencies of the combined dynamic system, including the train and the girder, are therefore well detuned. Hence, the effects of dynamic amplification are insignificant, and the girders can be analyzed according to the static axle loads for trains operating below 74 km/h.