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MATERIALS 59
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were supported at both ends and the loading points, and hypothesis of mechanically linked beams without considering
were spaced six times more than the panel thickness (6 h) shear deformation. As suggested by Brandner et al., Equations
between the center and either end of the opposite support. were used to calculate the bending stiffness by all three
The load was gradually increased, reaching a peak in about methods.

300 ± 120 s.
The extensometer linked to the testing apparatus determined Finite Element Modelling
the total deflection, while the connected PC recorded the As a composite material, the CLT panels were modelled
load–displacement curves. Using Equation, the global bending using ANSYS 2019 R13. The individual layers of CLT panels
stiffness (EImg) was calculated. were simulated as an orthotropic material with varying elastic
Following EN 16351, the RS strength was evaluated with characteristics in the longitudinal, tangential, and radial axes.
a short-span four-point bending test was conducted over the The model omitted wood imperfections such as knots,
span of nine times more than the thickness of the panel (9 h). cracks, annular rings, and other issues. The orthotropic CLT
Similarly to the bending test, ten replicate samples, with panels’ mechanical behaviour is determined by nine distinct

a total of 60 specimens, were examined for each adhesive elastic constants, including three elastic moduli (EL, ER, ET),
and layup. Both loading points were positioned at a distance three Poisson’s ratios (vLR, vLT, vRT), and three shear moduli
that was three times the panel thickness (3 h) from each end (GLR, GLT, GRT).
of the supports and their position ensured that they were The three-layer composite CLT panels were made of
spaced apart equally. orthotopically aligned poplar layers for homogenous poplar
The computer recorded the load–displacement curve CLT and outer maple with core poplar wood for hybrid CLT,
throughout the test, which was conducted using the UTM which were joined together with polyurethane (1C-PUR) and

Instron 5882 (Illinois ToolWorks Inc., Norwood, MA, USA) at melamine adhesive (ME) separately.
a 10 mm/min loading rate. The outer and core layers were connected without gaps;
The study used a randomised factorial design. A two-way their faces and edges could not slide or separate.
analysis of variance (ANOVA) was conducted using Statistica Since the outer and core layers were not edge bonded,
13 to assess the influence of wood species and adhesive type their interaction is modelled as friction. Tangential movements
on the bending and rolling shear properties of CLT panels. The are affected by friction. The coefficient of friction (f) was
Tukey HSD test (p < 0.05) was used to determine statistical assumed to be 0.5 for easier numerical modelling, based on
significance between datasets. Dobeš et al.’s findings that reported a coefficient of friction
In addition, this research used three widely used theoretical

methods: shear analogy (SA), Timoshenko beam theory (TBT),
and modified gamma (MG). According to SA, bending stiffness Theron Burger
is the product of the rigidity of the layer and Steiner’s stiffness
in proximity to the neutral axis.
TBT is an extended version of the Bernoulli–Euler theory
and calculates the flexural stiffness of CLT with the layer’s
characteristics and their arrangement while considering the

effect of shear.
The most widely used MG approach relies only on the