Application of Dynamic System Identification to Timber Beams. II

In a companion paper, a method of global nondestructive evaluation (NDE) for identifying local damage and decay in timber beams was developed and verified analytically using a finite-element model of a timber beam. The previously presented method of damage localization employs experimental modal analysis and an algorithm that monitors changes in modal strain energy between the mode shapes of a damaged beam with respect to the undamaged state of the beam. In this second part of a two-part paper, experimental laboratory tests on simply supported timber beams are presented to verify the capabilities and determine the limitations of the proposed method of NDE in locating simulated damage in simply supported timber beams. Due to the natural variability inherent within a timber beam, the required severity of inflicted damage before the algorithm could correctly identify damage location was a 5.08-cm (2-in.) deep saw cut in a beam with a depth of 15.88 cm (6.25 in.). For practical applications, the proposed technique could be used to identify the presence and general location of severe decay or damage, and if needed, more refined NDE techniques could be used to map the specific region affected by the decay or damage.