PSI - Issue 55

Dulce Franco Henriques et al. / Procedia Structural Integrity 55 (2024) 214–221 Henriques et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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3.1.2. By penetration resistance tests Penetration resistance testing was also carried out using a device for measurement of the resistance to penetration with energy of 6J, originally called pilodyn®, in areas with no apparent degradation. Seven tests were performed and the highest and lowest were rejected. The five readings considered suitable are shown in Table 1, with the values for each, their average and standard deviation. The estimated values for density and mechanical strength, obtained by correlation with the average of the measurements, are also presented. These correlations are the result of studies carried out by the first author published in Henriques et al. (2011) and Henriques (2024), from which the correlation equations (1) and (2) respectively, were drawn: Compressive strength: = ( ℎ −0,3−53702,409) (MPa) (1) Density: = ( ℎ −0,0−33029,295) (kg/m 3 ) (2) Where: -  i – estimated compressive strength of reading i - Depth i – reading i - ρ i – estimated density of reading i 3.1.3. By collection of wood cores and laboratory analysis As the collection of wood cores is a semi-destructive test, only one or two specimens were taken from each beam to check the values obtained from the penetration resistance tests. In the beam V1 one wood core was extracted. The wane zone was chosen for the extraction to ensure the radial / orthogonal direction to the rings, in order to accurately measure the growth rate (Fig. 3 (a)). Wood cores of the members were extracted using a 14 mm diameter cutter, which resulted in cuttings with a diameter of 7 mm and a maximum length of 16 cm (Fig. 3 (b) and (c)).

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Fig. 3. (a) Location of the wood core hole; (b) and (c) Measuring the dimensions of the wood core

From the laboratory analysis of the wood cores, it was possible to: • estimate the species of wood as Scots pine (Pinus sylvestris, L.); • observe that the growth of the wood was fairly regular, with a normal distribution of rings between the pith and the bark, with an average growth rate of 4.22 mm/year. • measure the dimensions and mass of the sample to calculate the wood density, after stabilization in a conditioned environment at RH = 65 ± 5 % and T = 20 ± 2 ºC which lead to a water content of 12%. The beam V1 had a low water content, with the average value of the measurements being 9% (table 1). However, the laboratory test on the wood core was carried out with a water content of 12%. For this reason, the density estimated by the in situ penetration resistance tests was corrected in order to make a proper comparison with the real density values obtained in the laboratory. For this correction, we used the empirical expression published by