An approach using experimental modal analysis (EMA) is presented for measuring the material damping properties of concrete beams. This approach, now popular in mechanical and aerospace engineering, uses hammerblow excitation and frequency-domain analysis to estimate resonance frequencies and modal damping. Damping properties quantified in this manner are compared to results obtained by traditional methods, which include log decrement and half-power bandwidth. The study demonstrates that damping values obtained using EMA compare favorably with those obtained using traditional methods—whether based on time- or frequency-domain approaches—and that data scatter was similar. The data allow identification of damping associated with particular frequencies or modeshapes, but without the inaccuracies associated with visual interpretation of time domain data or with the manual tuning of a shaker system. In addition, the study found no significant variation in damping with frequency, or with the presence or absence of passive reinforcement.
Amick, H., and P. J. M. Monteiro, “Experimental Determination of Modal Damping in Concrete Beams,” Materials Journal of the American Concrete Institute, May-June 2006, pp. 153-160.