Comparison of the estimated modal parameters of structures from classical and operational modal analysis with mass changes

The lack of standardization in vibration mode results has constituted the main shortcoming of operational modal analysis, subsequently resolved by means of the mass modification method. This is a major drawback for civil works, as it interrupts traffic on site, significantly increasing testing time and costs. The purpose of this study is to achieve a balance between traditional modal analysis (accompanied by numerical simulations of mass modification) and operational modal analysis (in conjunction with the mass modification method), thereby obtaining more optimal results with a narrower range of error, even when the signal has a high level of noise. It will thus be possible to reliably determine the modal parameters of the structure and their alteration due to mass modification. For this purpose, the proposed methodology is applied to a large span metal bridge, unique for its slenderness, with a span/depth ratio of 56.6, the lowest recorded on a bridge, as figured in the Guinness Book of Records since 2007