Overview of some non-destructive methods for in situ assessment of structural timber
2011
Teder, M., Estonian Univ. of Life Sciences, Tartu (Estonia). Dept. of Rural Building | Pilt, K., Estonian Univ. of Life Sciences, Tartu (Estonia). Dept. of Rural Building | Miljan, M., Estonian Univ. of Life Sciences, Tartu (Estonia). Dept. of Rural Building | Lainurm, M., Estonian Univ. of Life Sciences, Tartu (Estonia). Dept. of Rural Building | Kruuda, R., Estonian Univ. of Life Sciences, Tartu (Estonia). Dept. of Rural Building
The need for structural health assessment of old buildings can emerge in order to assure or extend their service life. In renovating buildings it is essential to assess the condition of timber structures. Often there are situations where the wood structures need to be evaluated on site and visual assessment is confined. At this point the non-destructive methods can be used for evaluation. This research uses ultrasonic, resistance drilling and pilodyn methods for the assessment of timber samples taken from currently existing buildings of different ages. As bending being the most important loading mode and modulus of elasticity is a good indicator of strength in timber structures the results of non-destructive methods were compared with them. Individual arguments like ultrasound velocity, moisture content, drilling resistance and relative hardness used in the regression analysis did not give a correlation above average in prediction of the bending strength and modulus of elasticity of wood found in the standardized bending test. The correlation between the density of timber and the readings of the resistograph was the strongest, especially damaged by fungi and beetles. Thereby, when the age of wood increased, the strength of it decreased. The correlation between the readings of the resistograph and timber internal stresses was weak, meaning that the resistance of wood does not change significantly while loaded with longitudinal forces.
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