Nondestructive assessment of wood beams using vibration response

A large number of wood poles are presently used in electrical power transmission industry in Canada. Many of these poles are subject to damage. Therefore wood poles need to be periodically examined for damage so that their in-service performance can be assured. The present study was initiated to examine the feasibility of applying vibration-based damage identification procedure to examine the integrity of transmission tower wood poles, having interior rotting or damage. The tower was represented by a rectangular cantilever beam model with the damage modelled as an interior rectangular slot. Three small-scale rectangular wood cantilever beams were tested using random excitation forces. Numerical and experimental studies were carried out. To identify and localise damage, a damage index was proposed. It was observed that the amplitude of the damage index increased significantly at a location which was close to the damage location, signifying that this index could be advantageously used to identify damage in such beams.