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Abstract. This research uses a non-destructive method -ultrasound -to examine timber, combining the results of measurement with the properties of strength and stiffness. The purpose of this work is to explore the possibilities of grading wood structure in situ using ultrasound measurements, specifically, the moisture content and density of the timber. The timber used in these experiments was taken from existing buildings of different ages. The potential of replacing direct measurements with indirect measurements by ultrasound was also investigated. The physical-mechanical properties of wood were determined in laboratory conditions according to standard practices, and the method of non-destructive measurements was based on a commercial test device based on 54 kHz compressional wave 50 mm diameter ultrasound transducers. Direct measurements were performed in the longitudinal and radial material directions. Indirect measurements were performed with transducers positioned on the same lateral surface of the sample. A weak correlation was found within the different measurements. Longitudinal measurements characterise bending strength with R 2 = 0.18 and modulus of elasticity with R 2 = 0.37. In multiple regression analysis, stronger correlations were found; prediction equations of bending strength and modulus of elasticity were found with R 2 = 0.40 and R 2 = 0.81, respectively.Keywords: acoustic measurement, bending strength, modulus of elasticity, density, moisture content, speed of sound, direct and indirect methods.

This paper reports an in situ inspection project conducted on heavy timber structures of a century-old industrial building at a paper manufacturing facility. A nondestructive inspection procedure was employed to evaluate the true condition of the heavy timbers that serve as the main framing structure of the building. The on-site investigation involved monitoring of the microclimate environment resulting from the paper machine operations, wood species identification, wood moisture content measurements, and internal decay detection using sounding, stress wave timing, and resistance micro-drilling methods. The testing results revealed that numerous locations were in poor condition indicated by widespread internal and external deterioration, reduced cross-sections from fire damages, and multiple failed members. Many timber members in the first floor exhibited a very high level of moisture condition (23 to 55%) as a result of high humidity air created by the paper making operations. This paper also showcases a new way of interpreting the evaluation results as straightforward as possible to the customer by creating 3D model-drawings and colored condition mappings.

Delamination and decay are common structural defects in old glued laminated timber (glulam) buildings, which, if left undetected, could cause severe structural damage. This paper presents a new damage detection method for glulam inspection based on moment analysis and wavelet transform (WT) of impact acoustic signals. Acoustic signals were collected from a glulam arch section removed from service through impact testing at various locations. The presence and positions of internal defects were preliminarily determined by applying time centroid and frequency centroid of the first moment. Acoustic signals were then decomposed by wavelet packet transform (WPT) and the energy of the sub-bands was calculated as characteristics of the response signals. The sub-bands of 0–375 Hz and 375–750 Hz were identified as the most discriminative features that are associated with decay and delamination and therefore are indicative of the presence of delamination or decay defects. A defect diagnosis algorithm was tested for its ability to identify internal decay and delamination in glulam. The results show that depth of delamination in a glulam member can be determined with reasonable accuracy.