The assessment of traffic-induced vibrations in urban areas by means of cost-effective sensors: a case study for a historic building in Trieste, north-eastern Italy

Traffic-induced vibrations represent a problem in urban areas where repeated dynamic loading from heavy vehicles can affect both the structural integrity of buildings and occupant comfort. This study addresses the dynamic response of a historic masonry building in the Borgo Teresiano district of Trieste, a site with Quaternary sediments known to amplify ground motions due to their low stiffness and heterogeneity. The aim was to investigate the interaction between traffic-induced ground motion and the structure’s response by using a rapid, non-invasive monitoring approach. During a short-term campaign, low-cost seismic stations with triaxial velocimeters were installed at the base and top of the structure. Ambient vibration data were analysed using: i) Fourier amplitude spectra combined with the rotation of horizontal components, ii) spectral ratios between sensor pairs within the structure to identify main structural modes and amplification directions, iii) single station horizontal-to-vertical spectral ratio analysis to identify fundamental soil resonance frequency. The results showed a resonance peak at 11 Hz in the vertical component at the top floor, interpreted as responsible for the amplification of vibrations caused by repeated traffic combined with soil-structure interaction, with levels exceeding discomfort thresholds and impacting wellbeing. This highlights how cost-effective sensors and ambient noise analysis support mitigation strategies.