The research presented is part of the SPP100+ of the German Research Foundation. Subject of the research is the early detection of damage, especially on large bridge structures. For this purpose, a large-scale experiment for vibration-based output-only damage detection was conducted at Flossgraben Bridge near Zeitz (Germany). The experiment was conducted over the course of three days for which the structure was equipped with 56 uniaxial piezoelectric acceleration sensors. The experimental structure is a healthy bridge structure constructed in 2001 and is part of the federal road B2 with two lanes for traffic. The bridge is composed of seven spans, with a total length of 358 m and a total weight of approximately 4750 t. The superstructure consists of an in-situ concrete slab resting on a trapezoidal, torsionally rigid steel box girder with inclined webs. The large-scale experiment was divided into a reference phase and two damage equivalent load case phases. Cargo trucks with a total mass of 39 t were used as additional mass and placed in field 4 and field 3 as mass alterations. During the complete course of the large-scale experiment one traffic lane was closed, while the other was open for traffic. The experiment was carried out with the kind support of the LSBB Saxony-Anhalt.