Latest revision as of 14:28, 30 November 2021

Abstract

Variations in environmental conditions can affect the structural performance of timber components and constructions. Especially in case of historic masonry buildings, where timber elements can be found either in roof or floor structures, intrinsic defects (e.g., knots, cracks, degradation), as well as the surrounding environmental conditions (e.g., temperature and moisture) can play an important role in the assessment of the mechanical response of the elements. In this connection, non-destructive (ND) and minor-destructive (MD) procedures are used to investigate the onsite conditions of wood, which are commonly based on either tool penetration resistance or wave transmission devices. In the paper, the influence of moisture content (MC) measured with various devices on a series of both old and new timber elements was compared. The elements made of various wood species (mainly red fir, but also white fir, pine and larch) were subjected to laboratory ND and MD testing by three research groups. Results showed the low influence of the MC on MD tests (i.e., resistance drilling and pin penetration) in comparison to the ND (i.e., sonic/ultrasonic) ones. Correlation relationships are provided, which illustrate and approximatively quantify the effect of MC for the experimentally investigated conditions and test equipment.

Full document

References

[1] Riggio, M., Anthony, R.W., Augelli, F., Kasal, B., Lechner T., Muller, W. and Tannert, T. In situ assessment of structural timber using non-destructive techniques. Materials an Structures, 47(5) (2013), pp 749–766.

[2] Piazza, M. and Riggio, M. Visual strength-grading and NDT of timber in traditional structures. Journal of Building Appraisal, 3 (2008), pp. 267-296.

[3] Tannert, T., Anthony, R.W., Kasal, B., Kloiber, M., Piazza, M., Riggio, M., Rinn, F., Widmann, R., Yamaguchi, N. In situ assessment of structural timber using semi destructive techniques. Materials and Structures, 47(5) (2013), pp 767–785.

[4] Drdácký, M. and Kloiber, M. In-situ compression stress-deformation measurements along the timber depth profile. Advanced Materials Research, 778 (2013), pp. 209-216,

[5] Kloiber, M., Drdácký, M., Tippner, J. and Hrivnák, J. Conventional compressive strength parallel to the grain and mechanical resistance of wood against pin penetration and microdrilling established by in-situ semidestructive devices. Materials and Structures, 48 (2015), pp. 3217-3229.

[6] Tippner, J., Kloiber, M., Sebera, V., Kunecký, J.: Health diagnostics of timber by continual pushing-through method. In: 17th International Conference on Experimental Mechanics (ICEM 17), 7/2016, Rhodes, Greece.

[7] Kloiber, M., Drdácký, M., Kunecký, J., Sebera, V., Tippner, J.: Mini-jack based direct determination of wood mechanical characteristics in situ. In: 17th International Conference on Experimental Mechanics (ICEM 17), 7/2016, Rhodes, Greece.

[8] Knag, H., Booker, R.E.: Variation of stress wave velocity with MC and temperature. Wood Science and Technology 36 (2002) 41–54 Springer-Verlag 2002, DOI 10.1007/s00226-001-0129-x

[9] UNI EN 338:2016 Structural timber - Strength classes.

[10] UNI 11119:2004 Cultural Heritage. Wooden artefacts. Load-bearing structures - On site inspections for the diagnosis of timber members.

[11] Uzielli, L. Il manuale del legno strutturale. Ispezione e diagnosi in opera. Mancosu, Vol. 1 (2006).

[12] Dackermann, U., Elsener, R., Li, J. and Crews, K. A comparative study of using static and ultrasonic material testing methods to determine the anisotropic material properties of wood. Construction and Building Materials, 102 (2016), pp. 963-976