PSI - Issue 78

Angelo Aloisio et al. / Procedia Structural Integrity 78 (2026) 25–32

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Table 2. Elastic constants adopted for C24 softwood [13]. Parameter

Symbol

Value

Young’s modulus, parallel to grain Young’s modulus, perpendicular to grain

E 11 E 22 ν 12 ν 13 ν 23 G 12 G 23

11000MPa E 11 / 30MPa

Poisson ratio, 1–2 Poisson ratio, 1–3 Poisson ratio, 2–3 Shear modulus, 1–2 Rolling shear modulus

0.30

0.036 0.018

E 11 / 16MPa G 12 / 10MPa

Table 3. Statistical descriptions of strength parameters [15, 4]. Property

Distribution

µ [MPa] CoV

Bending strength f m

Lognormal Lognormal

40 0.25

105

–

Tensile strength parallel tograin f 11 Tensile strength perp. to grain f 22

Weibull

4.5 0.25 8 0.25

Shear strength f 12

Lognormal

• Machine-learning models (logistic regression, linear SVM, random forest and XGBoost); • A transparent rule based only on the sum of hole diameters in two depth zones.

The rule is written in Eq. (8). A beam is marked Reusable when the predicted residual strength stays above 80 %; otherwise it is Non-reusable. Classify( k red ) =   k red ≥ 80% if � i ∈ Zone 1 d i > t 1  OR � i ∈ Zone 2 d i > t 2  k red < 80% otherwise (8) where t 1 and t 2 are fixed thresholds for zones No.1 and 2. The numbering of the zones corresponds to the numbers shown in Fig. 2, where zone No. 1 identifies the two external longitudinal zones, and No. 2 refers to the inner zone.

Fig. 2. Depth partition used for feature extraction.

Alternative metrics, largest diameter, hole count, mean or standard deviation of diameters, were tested, but the summed diameter in each zone yielded the clearest separation between safe and unsafe cases. Holes near the highly stressed fibres (top and bottom edges) matter most, while those close to the supports had almost no influence in the lab series D–H of [22]. Hence only the span middle is considered, and the outer quarter depth strips are checked independently of the core. For everyday inspection the following conservative rules apply: • ignore holes smaller than 3 mm (their e ff ect proved negligible); • accept that the edge zones can be skipped entirely if the total diameter in both is below 100 mm and no hole exceeds 30 mm.