First Trials for a Microwave Reflectometric Tool to Survey Decay in Historic Timber Structures

Abstract

Timber structures can be degraded during their life both by structural problems and by biological degradation factors like fungi, and insects. The occurrence of those biodegradation agents could lead to a loss of their structural integrity, in the absence of appropriate maintenance. An early assessment of the decay is even more important when the wooden structures are part of historical buildings, in the interest of conservation of cultural heritage. This work presents an application of microwave reflectometry for the in situ evaluation of timber structures. The measurement system allows detecting anomalies inside the material in a non-destructive and non-invasive manner. The reflection coefficient is measured by means of a vector network analyzer (VNA) using a double-ridge antenna, which transmits the continuous-wave microwave signal and receives the signal reflected by the material under investigation. Measurements on laboratory models demonstrated the feasibility of the method. Results obtained on timber beam sections, compared with the findings of traditional investigation methodologies, demonstrate the potentiality of microwave reflectometry, suggesting its possible usefulness during the diagnostic phase as a non-invasive tool for preliminary screening.