Title:
Experimental Determination of Modal Damping
in Concrete Beams
Author(s):
Hal Amick and Paulo J. M. Monteiro
Publication:
Materials Journal
Volume:
103
Issue:
3
Appears on pages(s):
153-160
Keywords:
analysis; deformation; testing; water-cement ratio.
DOI:
10.14359/15848
Date:
5/1/2006
Abstract:
An approach using experimental modal analysis (EMA) is presented for measuring the material damping properties of concrete beams. This approach, now popular in mechanical engineering, uses hammer-blow excitation and frequency-domain analysis to estimate resonance frequencies and modal damping. The data allow identification of damping associated with particular frequencies or mode shapes, but without the inaccuracies associated with visual interpretation of time domain data or with the manual tuning of a shaker system. The study found no significant variation in damping with frequency, or with the presence or absence of passive reinforcement. Damping was shown to decrease by approximately 25% between the ages of 4 and 18 weeks. At 4 weeks, damping was found to increase with the water-cement ratio (w / c) in a manner that depended on deformation type (that is, extensional, bending, or torsional). At 18 weeks, however, damping decreased slightly with the w/ c in a manner that was essentially independent of deformation type.