Measurement of dynamic properties of a composite frame railway bridge – Field testing of the railway bridge crossing Salzach River in Schwarzach/St. Veit, Austria. A prefabricated composite frame bridge was measured at four different stages during construction phase and after opening to railway traffic. The performed measurements were used to analyze the contribution of backfill to dynamic behavior of the bridge under vertical excitation. At the first measurement, different kinds of accelerometers and afterwards different analysis methods were used. Both led to the same eigenfrequencies. The three subsequent measurements were analyzed with only one of those methods. At the investigated bridge, only a negligible contribution of the backfill could be observed. This paper introduces the first obtained results and discusses which observations can be transferred to other bridges.