The dataset contains experimental measurement data of a 1.205 m long laboratory steel cantilever beam. The cantilever beam is a modular setup of a central beam structure with nine screwed-on fishplates. The fishplates are used to implement a variable, reversible damage mechanism. The experiment was conducted in the laboratory hall of the Institute of Structural Analysis of the Leibniz University Hannover. The central beam with nine undamaged screw-on fishplates represents the reference state of the experiment considered. The reversible damage mechanism is activated by swapping the intact fishplates with damaged fishplate specimens. Acceleration data is recorded using fifteen miniature IEPE accelerometers that are connected to the central beam structure. Three different damage scenarios were introduced, thus, the dataset comprises three measurement series. Each measurement series involves screwing the respective damaged fishplate specimen onto all nine fishplate positions in sequence. In addition, before the measurement of each damaged state of the cantilever beam, the reference state is restored and a measurement of this intact state is conducted. For further information, it is referred to „Wolniak et al., Validation of an FE model updating procedure for damage assessment using a modular laboratory experiment with a reversible damage mechanism, Journal of Civil Structural Health Monitoring (2023), doi: 10.1007/s13349-023-00701-9“.