Comparison of OMA techniques and effect of added masses on the modal properties of a small steel frame

An output-only vibration test was conducted on small steel frames during the OMA course at the 6th International Operational Modal Analysis Conference (IOMAC 2015). These structures were excited by human-hand-induced vibrations and tested with and without additional masses. This paper presents the data analysis on one of the structures that were tested. The objectives of this analysis are to compare two different OMA techniques (i.e. EFDD and NExT-ERA) and to investigate how the identified modal parameters of the structure are varied in case of added masses. Identified natural frequencies, modal damping ratios and mode shapes are in good agreement between the two selected OMA techniques. The results also show that modal damping ratios increased with additional masses on the structure.