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Embedment strength of mixed-species laminated veneer lumbers and cross-banded laminated veneer lumbers

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This paper experimentally evaluates the embedment strength of laminated veneer lumbers (LVL) and cross-banded laminated veneer lumbers (LVL-C) manufactured from blending spotted gum (Corymbia citriodora) or white cypress pine (Callitris glaucophylla) veneers with hoop pine (Araucaria cunninghamii) veneers. Nominal 3.0 mm thick veneers were rotary peeled from small diameter (less than 30 cm) native forest sourced spotted gum and white cypress pine logs, and plantation grown hoop pine logs. 12-ply × 1.2 m (long) × 0.9 m (wide) LVL and LVL-C panels were manufactured using ten different construction strategies by mixing (i) the number of veneers from each species, (ii) the modulus of elasticity of the veneers and (iii) the veneer orientations (cross-banding). A total of 672 embedment tests, using three different dowel diameters and four different load-to-grain orientation angles, were performed using the half-hole test method described in the ASTM D5764-97a. This paper (i) compares the proportional limit strength, 5%-offset embedment strength and maximum embedment strength across the different construction strategies adopted in the study, and (ii) discusses the results in terms of load-to-grain angle and dowel diameter. More importantly, the test results are also compared to the embedment strength prediction equations detailed in the Eurocode 5 to determine their suitability for mixed-species LVL and LVL-C products. Overall, the mixed-species LVL and LVL-C showed significantly higher 5%-offset embedment strengths than single-species commercial softwood LVL products. The effect of the cross-banded veneers on the embedment strength was not found to be significant. However, the LVL-C samples exhibited a highly ductile behaviour for all load-to-grain angles and dowel diameters when compared to the LVL samples. The experimentally determined 5%-offset and maximum embedment strengths for the mixed-species LVL were on average equal to and 7% higher than the predicted values given in Eurocode 5.
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Vol.:(0123456789)
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European Journal of Wood and Wood Products (2020) 78:365–386
https://doi.org/10.1007/s00107-020-01504-1
ORIGINAL
Embedment strength ofmixed‑species laminated veneer lumbers
andcross‑banded laminated veneer lumbers
HoanH.Nguyen1 · BenoitP.Gilbert1· RobertL.McGavin2· HenriBailleres2· HassanKarampour1
Received: 4 June 2019 / Published online: 6 February 2020
© Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract
This paper experimentally evaluates the embedment strength of laminated veneer lumbers (LVL) and cross-banded laminated
veneer lumbers (LVL-C) manufactured from blending spotted gum (Corymbia citriodora) or white cypress pine (Callitris
glaucophylla) veneers with hoop pine (Araucaria cunninghamii) veneers. Nominal 3.0mm thick veneers were rotary peeled
from small diameter (less than 30cm) native forest sourced spotted gum and white cypress pine logs, and plantation grown
hoop pine logs. 12-ply × 1.2m (long) × 0.9m (wide) LVL and LVL-C panels were manufactured using ten different construc-
tion strategies by mixing (i) the number of veneers from each species, (ii) the modulus of elasticity of the veneers and (iii) the
veneer orientations (cross-banding). A total of 672 embedment tests, using three different dowel diameters and four different
load-to-grain orientation angles, were performed using the half-hole test method described in the ASTM D5764-97a. This
paper (i) compares the proportional limit strength, 5%-offset embedment strength and maximum embedment strength across
the different construction strategies adopted in the study, and (ii) discusses the results in terms of load-to-grain angle and
dowel diameter. More importantly, the test results are also compared to the embedment strength prediction equations detailed
in the Eurocode 5 to determine their suitability for mixed-species LVL and LVL-C products. Overall, the mixed-species
LVL and LVL-C showed significantly higher 5%-offset embedment strengths than single-species commercial softwood LVL
products. The effect of the cross-banded veneers on the embedment strength was not found to be significant. However, the
LVL-C samples exhibited a highly ductile behaviour for all load-to-grain angles and dowel diameters when compared to the
LVL samples. The experimentally determined 5%-offset and maximum embedment strengths for the mixed-species LVL
were on average equal to and 7% higher than the predicted values given in Eurocode 5.
1 Introduction
Connections with dowel-type fasteners are very common
in timber structures and are generally deemed to be the
weakest structural link (Leijten 1993). This type of connec-
tion can be either ductile, brittle or a combination of both
(Habkirk 2006; Quenneville and Mohammad 2000; Quen-
neville 2008). To estimate their ductile failure capacity, the
European Yield Model (EYM) (Johnsen 1949) forms the
basis of the prediction equations in standards such as the
Eurocode 5 (EN1995-1-1 2004), and is considered to be
accurate (Franke and Quenneville 2011). In this model, the
embedment strength of the timber is one of the key input
parameters to determine the overall connection capacity and
is related to the capacity of wood or wood-based products to
resist the force induced by a rigid fastener.
The estimation of the embedment strength of various
timber species and fastener types has been extensively stud-
ied, see Ehlbeck and Werner (1992), Hirai (1989), Hübner
(2008), Larsen (1973), Whale etal. (1986, 1989), Wilkinson
(1991) for instance. This led to the development of vari-
ous forms of empirical equations. Wilkinson (1991) derived
Eqs.(1) and (2) (in psi and inches) below for the 5%-offset
embedment strength (ASTM D5764-97a 2018) from tests
performed on several softwood and hardwood species with
load-to-grain angles of 0° (parallel to grain) fh,0 and 90°
(perpendicular to grain) fh,90. These equations were con-
structed based on the timber specific gravity (G) (i.e. the
ratio between the weight densities of timber and water) and
* Hoan H. Nguyen
hoan.nguyenhai@griffithuni.edu.au;
nguyenhaihoanvfu@gmail.com
1 School ofEngineering andBuilt Environment, Griffith
University, Brisbane, QLD, Australia
2 Queensland Department ofAgriculture andFisheries,
Horticulture andForestry Science, Salisbury Research
Facility, Brisbane, QLD, Australia
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... Confirming the study´s results, hybrid products using low-quality hardwood such as mixed hardwood LVL Nguyen et al. 2020, innovative mixed-hardwood pulp (Olsson et al. 2019), and mixed soft-and hardwood pulp (Fišerová et al. 2019) are actually under investigation. ...
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