Investigation of Transmissibility-Based Operational Modal Analysis from Ground Excitation

Transmissibility-based operational modal analysis (TOMA) can be used to determine the modal parameters under different excitations, where no assumptions about the nature of the excitations are required. Classical OMA methods are based on the assumption that the excitation is white noise. However, this cannot always be satisfied. Ground vibrations caused by rail, road traffic or construction site operations represent various excitations for the building. These excitations can also contain harmonic components. By using TOMA, the restriction to white noise can be abandoned. Furthermore, the application of TOMA from ground excitation has not been properly addressed yet. This study is performed using experimental data from a 2-story timber structure resting on a concrete slab under laboratory conditions. Ground excitation is applied using a vibration test system on the slab. The identification focuses on the first floor, where frequency, damping, and mode shapes are identified. Several aspects are examined, such as the influence of the number of sensors as well as the level and type of excitation. Moreover, TOMA is compared to the poly-reference least squares frequency domain estimator (p-LSCF) method. The results show the potential of TOMA for the monitoring of buildings even when only subjected to small ground excitation or with few numbers of sensors.