Operational modal analysis of a ten-storey building featuring vertical modes

As a contribution to addressing challenges and improving technology in field implementation and practice of ‘operational modal analysis’ (OMA), a vibration test was carried out on a 10-storey rectangular building, featuring modal identification for both horizontal and vertical axes over a grid of 80 locations. The study used six triaxial accelerometers in 20 setups and the particular challenges with data are with close/buried modes, significant noise disparity, and contamination with harmonic signals in two frequency bands around 2 Hz and 8 Hz, which are addressed using recently developed techniques in Bayesian OMA. A particular feature of the building dynamic behaviour in the higher band of modes revealed by the study was a set of global vertical vibration modes. In addition to the short-term multi-setup test, two months of monitoring data were collected using a single accelerometer on the top floor to study amplitude dependence and ensemble statistics of modal properties, particularly for the first horizontal mode. The results reveal that the natural frequencies of the first three modes decrease with the vibration level while the damping of the first mode shows an increasing trend. The field data used in this study are archived in an open repository for public access.