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This study investigates the bending and bonding performances of glued laminated timber beams manufactured using a combination of Malaysian lower and higher- grade timber species. Two types of beams were prepared which were mono-species and mixed-species glulam. Mono-species glulam with uniform layup were fabricated using Merpauh, Jelutong and Sesendok. Mixed-species glulam with balanced layup were fabricated whereby Merpauh was positioned equally at the outer layers and either Jelutong or Sesendok were positioned at the inner layers. Three replicates of ten-layered glulam beams measuring 100 mm in width, 300 mm in depth and 6200 mm in length were manufactured according to MS758 for each mono and mixed-species glulam. Bending, delamination and block shear tests were done on all the glulam beams. The results show that glulam manufactured from the combination of Sesendok and Merpauh obtained the highest bending properties and structural efficiency. In addition, the bonding performance at the interface between Sesendok-Merpauh lamellas proved to be excellent.
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81:4 (2019) 165170 | | eISSN 21803722 |DOI:|
Full Paper
Wan Hazira Wan Mohamada, Norshariza Mohamad Bhkarib,
Zakiah Ahmadb*
aFaculty of Applied Sciences, Universiti Teknologi MARA
Malaysia, 40450 Shah Alam, Selangor, Malaysia
bFaculty of Civil Engineering, Universiti Teknologi MARA
Malaysia, 40450 Shah Alam, Selangor, Malaysia
Article history
12 March 2018
Received in revised form
16 January 2019
15 May 2019
Published online
25 June 2019
*Corresponding author
Graphical abstract
This study investigates the bending and bonding performances of glued laminated
timber beams manufactured using a combination of Malaysian lower and higher-
grade timber species. Two types of beams were prepared which were mono-species
and mixed-species glulam. Mono-species glulam with uniform layup were fabricated
using Merpauh, Jelutong and Sesendok. Mixed-species glulam with balanced layup
were fabricated whereby Merpauh was positioned equally at the outer layers and
either Jelutong or Sesendok were positioned at the inner layers. Three replicates of
ten-layered glulam beams measuring 100 mm in width, 300 mm in depth and 6200
mm in length were manufactured according to MS758 for each mono and mixed-
species glulam. Bending, delamination and block shear tests were done on all the
glulam beams. The results show that glulam manufactured from the combination of
Sesendok and Merpauh obtained the highest bending properties and structural
efficiency. In addition, the bonding performance at the interface between
Sesendok-Merpauh lamellas proved to be excellent.
Keywords: Glulam, Mixed-species, Bending properties, Bonding properties,
Delamination, Shear glue line
Kajian ini dijalankan bagi melihat prestasi lenturan dan lekatan bagi rasuk kayu
berperekat yang dihasilkan melalui gabungan kayu tropika Malaysia dari spesis kayu
berkekuatan rendah dan kayu berkekuatan tinggi. Dalam kajian ini, dua jenis rasuk
telah dibangunkan iaitu dari spesis tunggal sebagai sampel kawalan dan juga rasuk
dari spesis campuran. Rasuk dari spesis tunggal dibina secara seragam dengan
menggunakan spesis kayu Merpauh, Jelutong dan Sesendok. Rasuk spesis campuran
pula dibina dengan kedudukan simetri di mana lapisan luar pada bahagian atas
dan bawah rasuk adalah dari spesis kayu Merpauh manakala bahagian lapisan
dalaman adalah dari spesis kayu Jelutong atau Sesendok. Bagi ujikaji makmal, tiga
batang sampel dari setiap rasuk kayu berperekat dari spesis tunggal dan spesis
campuran telah dibina. Sampel rasuk yang dibina ini terdiri daripada sepuluh lapisan
kayu panel yang dilekatkan dengan keratan rentas rasuk berukuran 100 mm lebar
dan 300 mm dalam. Panjang setiap rasuk pula berukuran 6200 mm. Semua rasuk ini
dibina berpandukan standard Malaysia, MS758. Ujikaji lenturan, delaminasi dan blok
ricihan telah dijalankan ke atas semua sampel kajian. Keputusan kajian
menunjukkan rasuk kayu berperekat dari spesis campuran Sesendok dan Merpauh
telah memperolehi sifat lenturan yang tinggi dan mempunyai struktur rasuk yang
lebih kuat berbanding dari sampel rasuk yang lain . Dalam kajian ini juga, prestasi
lekatan bagi antara muka lapisan kayu bagi rasuk spesis campuran Sesendok dan
Merpauh dibuktikan lebih baik.
Kata kunci: lapisan kayu berperekat, spesis kayu campuran, sifat lenturan, sifat
lekatan, delaminasi, ricihan garisan lekatan
© 2019 Penerbit UTM Press. All rights reserved
Glued Laminated
Timber (Glulam)
Mono and mixed-
species using Merpauh,
Jelutong and Sesendok
Bending and Bonding
166 Wan Hazira, Norshariza & Zakiah / Jurnal Teknologi (Sciences & Engineering) 81:4 (2019) 165170
Glue laminated timber is defined in ASTM D3737
Standard Practice Establising Allowable Properties
of Structural Glued Laminated Timber (Glulam) as
“a material glued up from suitably selected and
prepared pieces of wood whether in straight or
curve form with the grain of all pieces essentially
parallel to the longitudinal axis of the member.
Structural glulam is one of the oldest and
established structural members and is widely used
in developed country yet in Malaysia, the usage is
only gaining acceptance in the construction
industry. Recently, the Malaysia Timber Industry
Board built an iconic glulam building using Resak
and Keruing in Johor and it was recognized as the
first building completed using glulam in Malaysia.
Another recently completed project incorporating
glulam is the Head Quarters of the Crops for the
Future in Semenyih, Selangor.
One of the important characteristics in glulam
manufacturing is that bonding of laminations
produces beams with higher strength as compared
to the strength of solid timber with the same
dimensions [2]. This increase in strength is important
because the quality of lamination is dependent on
its magnitude. Laminating also allows the dispersion
of timber defects throughout the length of the
glulam member by redistributing stress of the
defect through the clear wood of adjacent
laminations [3]. In addition, laminating allows
control over the positioning of different grades of
timber within the glulam member cross-section. By
placing the strongest timbers in the regions of
greater stress e.g. the top and bottom of a
bending member, the performance of the glulam
members can be further enhanced [4].
Nearly any species or mixed-species
combination can be used to manufacture glulam,
provided its physical, mechanical and bonding
properties are suitable and the timbers can be
glued together [2]. Glulam members
predominantly consist of softwood as they are the
main source of structural timber, however
hardwoods are slowly gaining importance in
glulam production [5]. Mixed species combination
commonly used in the United States include
Douglas Fir (Pseudotsuga menziesii)Larch (Larix
occidetalis), Hemlock (Tsuga heterophylla)
Douglas Fir and Spruce (Picea spp.)Pine (Pinus
spp.)FirRed Maple (Acer spp.) [6]. Other mixed
species combination studied by other reserachers
includes Poplar (Populus X euramaricana) -
Eucalyptus (Eucalyptus grandis) [4] as well as Sugi
(Cryptomeria japonica) - Hinoki (Chamaecyparis
obtuse) and Douglas Fir [7].
Although extensive research has been
conducted on glulam [8-11], limited studies have
been conducted to investigate the physical and
mechanical properties of glulam using Malaysian
hardwood timbers. Among the recent studies
conducted include works done by Wan Mohamad
et al. (2011), Wan Hazira et al. (2014) and
Norshariza et al. (2014 and 2016]. Wan Mohamad
et al. (2011) studied the bending strength of Resak
and Keruing glulam and reported that the
maximum bending capacity of both glulam beams
were higher than the allowable bending strength
stated in MS544 Part 3. This indicates that glulam
beam using Malaysian timber is suitable as
structural members. It was also found that glulam
fabricated using lower density timber namely
Merpauh (Strength Group 4) and Bintangor
(Strength Group 5) was able to improve the
strength of the timber through glulam technology
(Wan Hazira et al., 2014). However, for timber with
higher density (such as Strength Group 2 and
Strength Group 3), the bending strength of glulam
was at par with the bending strength of solid timber
for that particular strength grade [14-15].
In Malaysia, heavy and medium hardwoods
(SG1-SG4) are normally used as load bearing
members. However not all of these species are
suitable for glulam manufacturing. These higher
grades, higher density timbers have difficult gluing
characteristics and are expensive. On the other
hand, light hardwoods (SG4-SG7) are mostly used
for non-structural applications and do not
represent efficient use of available timber. One
way of fully utilizing and upgrading these timbers is
by converting them into glulam and by combining
with proven high quality timber species. The main
objective of this study is to determine the effect of
using Malaysian lower-grade species combined
with higher-grade species on the bending and
bonding properties of glulam beams.
2.1 Materials
The species used to manufacture glulam beams
were Merpauh (Swintonia spp.), Jelutong (Dyera
spp.) and Sesendok (Endospermum spp.). The
strength group and density of each timber species
are shown in Table 1. The species selected is based
on availability and strength groups namely SG4 for
Merpauh, SG6 for Jelutong and SG7 for Sesendok.
Phenol resorcinol formaldehyde (PRF) adhesive
and hardener obtained from Dynea NZ Limited
(Prefere 4001-2 and Prefere 5837) were used during
end jointing and lamination.
Table 1 Strength group and density of timber species
Timber species
Strength Group
(SG) [16]
Density (kg/m3)
640 880
415 495
305 - 655
2.2 Specimen Preparation
All timbers used for glulam manufacturing were
graded into Hardwood Structural (HS) grade in
accordance with MS1714. Two types of glulam
beams were prepared; (i) mono-species with
uniform layup and (ii) mixed-species with balanced
166 Wan Hazira, Norshariza & Zakiah / Jurnal Teknologi (Sciences & Engineering) 81:4 (2019) 165170
layup (Figure 1). Three mono-species glulam were
prepared using only Merpauh, Jelutong and
Sesendok. For the mixed-species glulam, the
positioning of the higher and lower strength grade
timber in a beam was according to
recommendations made in MS544 Part 3. The
higher strength grade timber species i.e. Merpauh
were equally positioned at the outer layers while
the lower grade timber species, namely Jelutong
and Sesendok were positioned at the inner layers
of the beam. The depth of the higher-grade
species was 40% of the total glulam beam depth.
The lower grade species for the inner lamella was 2
to 3 grades lower than the outer lamella, as shown
in Figure 1. The compositions of the mixed-species
glulam were Jelutong-Merpauh and Sesendok-
Merpauh. The glulam beam manufactured had
dimensions of 6200 mm in length by 100 mm in
width and 300 mm in depth, as shown in Figure 2.
Figure 1 Beam composition of glulam
Figure 2 Dimension of glulam
2.3 Test Method
2.3.1 Bending Test
A three-point load bending test was set-up as
shown Figure 3. The test was conducted according
to ASTM D198. The bending strength, SR and
modulus of elasticity, Ef were calculated according
to the following equations. The actual bending test
set-up is shown in Figure 4.
 
 (1)
 
 (2)
where Pmax is the maximum load borne by beam
loaded to failure (N), L is the span of the beam
(mm), b is the width of the beam (mm), h is the
depth of the beam (mm), a is the distance from
reaction to nearest load point (1/3 shear span)
(mm), P is the increment of applied load below
proportional limit (N) and Δ is the increment of
deflectioin of beam’s neutral axis measured at mid
Figure 3 Schematic diagram of bending test set-up
Figure 4 Actual bending test set-up
2.3.2 Delamination Test
Delamination test was conducted in accordance
with MS758. Method A was applied because the
adhesive used in this study to manufacture glulam
beams was Type I Adhesive. The specimens for
delamination test were extracted from the full cross
section of the glulam beam and represented the
glulam production run. The specimens were cut
perpendicular to the grain of the glulam member
and had dimensions of 75 mm in length (along the
grain) by 100 mm in width and 300 mm in depth.
Five replicates were tested for each glulam beams.
The test specimens were subjected to two test
cycles and an extra cycle was carried out for test
specimens having a total delamination
percentage of 5 and above. The lengths of the
open glue lines on end grain surface for each test
specimen were measured at the end of the test.
2.3.3 Block Shear Test
Block shear test on the glue lines were conducted
according to MS758. The test specimens were
taken from the full cross-section of the glulam
beam and 1100 mm away from the edge of the
beam. Specimens were cut perpendicular to the
grain direction. All nine glue lines of each glulam
beam specimens were tested. The dimension of
the test specimens were 50 mm in length by 50 mm
167 Wan Hazira, Norshariza & Zakiah / Jurnal Teknologi (Sciences & Engineering) 81:4 (2019) 165170
in width and 50 mm in depth, with the glue line at
the center of the specimen. A 1000 kN universal
testing machine was used to test all the specimens.
Constant load was applied and load readings was
continuously detected and recorded up to the
ultimate load, after at least 20 seconds. Shear
strength were calculated and wood failure
percentage were also determined.
3.1 Bending Properties of Glulam
The bending properties of mono and mixed-
species glulam beams were analyzed in terms of
modulus of rupture (bending strength) and
modulus of elasticity. Three replicates were tested
for each glulam beam and the mean and
coefficient of variation (COV) was calculated.
From Figure 5 and Figure 6, a clear difference
between mixed Sesendok-Merpauh and others
can be seen, both in the case of mono and mixed-
species glulam. Figure 5 shows that the highest
modulus of elasticity, with respect to Merpauh was
obtained using mixed Sesendok-Merpauh
(+35.73%) while mixed Jelutong-Merpauh showed
lower increase (+20.10%).
Figure 5 Modulus of elasticity in static bending
In the case of bending strength, as shown in Figure
6, the maximum increase (+36.50%) with respect to
Merpauh was also found for mixed Sesendok-
Merpauh glulam while mixed Jelutong-Merpauh
showed lower increase (+18.68%).
Out of the two mixed-species glulam, Sesendok-
Merpauh obtained the highest bending properties
whereby the percent increase of bending strength
was 36.50%, 4.86% and 28.83% when compared
against Merpauh, Jelutong and Sesendok,
respectively. In addition, the percent increase of
modulus of elasticity for Sesendok-Merpauh glulam
when compared against Merpauh, Jelutong and
Sesendok were 35.73%, 141.84% and 156.75%
Table 2 shows the summary of the mean values
for density, bending strength modulus of elasticity
and structural efficiency for all glulam beams
studied. The COV values are quite low indicating a
low dispersion of mean values for both bending
strength and modulus of elasticity.
Figure 6 Bending strength
Table 2 Mean values, coefficient of variation and structural effciency of each species of beams for the bending
Bending strength
efficiency for
Bending strength
Modulus of
efficiency for
Modulus of
8.69 (0.66)
31.75 (7.15)c
17800 (0.56)c
Mixed Jelutong-
626 (1.88)
37.68 (2.44)ab
21370 (8.56)b
Mixed Sesendok-
613 (1.15)
43.34 (13.73)a
24160 (8.49)a
492 (2.39)
41.33 (1.4)a
9990 (12.61)d
487 (1.93)
33.64 (6.78)bc
9410 (2.55)d
Note: COV in parentheses. Same letters are not significant at 0.05 according to Duncan’s Multiple Range Test.
Modulus of Elasticity (N/mm2)
Bending strength (N/mm2)
168 Wan Hazira, Norshariza & Zakiah / Jurnal Teknologi (Sciences & Engineering) 81:4 (2019) 165170
The load displacement curve under bending for all
the beam studied is presented in Figure 7.
Generally, all the beams had linear elastic
behavior until failure occurred. The curve pattern
indicated brittle behavior because all the beams
failed abruptly after reaching ultimate load.
Mixed-species glulam obtained higher ultimate
load compared to mono-species glulam, which
indicates that mixed-species glulam beams are
able to sustain bigger load when subjected to
Figure 7 Load versus displacement curve
3.2 Delamination in the Glue Line
Figure 8 shows the average total delamination
percentages after two cycles for all the glulam
beams studied. The data indicates excellent quality
of the glue lines in both mono and mixed species
glulam beams. Eventhough Merpauh showed
mixed results whereby one replicate exceeded the
allowable maximum value set forth in MS758, the
mean value of the average total delamination
percentage for Merpauh was 4.3% which is below
the maximum requirement value of 5%. Low
delamination percentage in the glue lines between
Merpauh and Jelutong as well as Merpauh and
Sesendok indicated non-existance of gluing
problems at the interface between these wood
species. This could be due to the similarity in
shrinkage values for the species studied, as shown
in Table 3.
Figure 8 Average total delamination after two initial
cycles in percentage
Table 3 Shrinkage percentages of Merpauh, Jelutong and
Shrinkage percentage (%)
(S. Schwenkii)
(Dyera spp.)
(Endospermum spp.)
Note: Data obtained from a dictionary of Malaysian Timbers [12].
3.3 Shear Strength of Glue Line
The average glue line shear strength and relative
wood failure of all the glulam beams studied are
summarized in Table 4. Generally, all the glulam
beams fulfill the MS758 requirement which set forth
a minimum of 6.0 N/mm2 shear strength, while for
lighter density timber, a shear strength of 4.0 N/mm2
is acceptable provided the wood failure
percentage is 100%. For wood failure that did not
reach 100%, the values obtained were compared
against the acceptance criteria stated in MS758.
For shear strength of 11 N/mm2, the minimum wood
failure must be above 45% thus Merpauh, mixed
Jelutong-Merpauh and mixed Sesendok-Merpauh
met the requirement.
For shear strength of 8 N/mm2, the minimum
wood failure must be above 72% so both Jelutong
and Sesendok met the requirement. This indicates
good load carrying capability of the glue line in all
the glulam studied as well as confirms the reliability
of bonding found in the delamination tests.
020 40 60 80 100 120
Load (kN)
Displacement (mm)
Merpauh Mixed Jelutong-Merpauh
Mixed Sesendok-Merpauh Jelutong
Average total delamination (%)
Replicate 1 Replicate 2 Replicate 3
169 Wan Hazira, Norshariza & Zakiah / Jurnal Teknologi (Sciences & Engineering) 81:4 (2019) 165170
Table 4 Shear strength and relative wood failure
8.07 (7.33)
9.56 (15.27)
Note: COV in parentheses.
For all the glulam beams studied, mixed species
beams showed higher bending properties as well
as structural efficiency than those constructed
entirely from Merpauh, Jelutong or Sesendok. The
best bending performance between mixed species
glulam is the combination of Sesendok and
Merpauh. In addition, the excellent quality of the
glue lines between laminates also contributed to
the performance of the glulam beams. The results
obtained from this study confirm the possibility of
producing high structural efficiency glulam beams
by combining two different timber species.
Malaysia Timber Industry Board (MTIB) financially
supported the work reported here. We wish to
thank the technicians of Civil Engineering Faculty,
Universiti Teknologi MARA (UiTM) and Loji
Pengeringan Tanor MTIB, Konsortium PEKA Sdn Bhd
for their assistance and support.
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... Authors also remarked the high importance of an accurately grading of the planks during the design process. In [15][16][17], the authors also combined different species of wood with the same final conclusion of low-grade, high-grade timber distribution for inner and outer parts of the glulam timber, respectively. Furthermore, this conclusion has been recently extended to CLT (Cross Laminated Timber) panels [18]. ...
... Furthermore, this conclusion has been recently extended to CLT (Cross Laminated Timber) panels [18]. In [16], when a high-grade wood such as Merpauh was used for the outer planks, improvements of the modulus of elasticity between 117% and 157% were achieved. ...
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... Tomasi et al. (2009) have tested poplarlarch glulam and poplar-spruce glulam beams to find that optimal results are possible when the strength limits of the two wood species are significantly different. Mohamad et al. (2019) have studied the bending and bonding performance of glulam beams manufactured using a combination of wood species with different strength class. Sesendok-Merpuah mixed species beams show the best bending performance, bonding performance, and structural efficiency, with a 35.73% increase in elastic modulus and 36.50% increase in bending strength over Merpuah glulam beams. ...
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... Glulam was composed of wood laminate with parallel laminae toward the preparation of fibers and then glued with an adhesive [9]. Glulam has advantages, one of which resulted in a higher strength beam than solid wood in the same dimension [10]. Glulam can be produced from small-diameter wood by [11]. ...
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The purpose of this study is to evaluate shear strength and improve the resistance of glulam from sengon (Falcataria moluccana) wood through the preliminary treatment of polystyrene impregnation. Sengon laminas were impregnated with polystyrene and made into two-layer glulam using isocyanate adhesives. The glulam was tested for shear strength according to American Standard for Testing Materials D-905-98, and exposed to subterranean termite attack in the laboratory scale according to Indonesian standard SNI 7207-2014. The untreated glulam and solid wood were used as a comparison purposes, and the tested samples were six replicas. The polymer loading of polystyrene glulam was 28.7%. The results showed that shear strength of solid wood was not significantly different from glulam, it means that impregnation process of the styrene on sengon wood does not affect the gluing process. The polystyrene impregnated glulam had better resistant to termite attack than solid wood, but it was not significantly different from the untreated glulam. To get better resistance it could be further study for higher polymer loading in glulam manufacturing.
... To date, some of the literature reported on the bonding performance of tropical hardwoods (Martins et al. 2019;Malek et al. 2019;Mohamad et al. 2019;Yusof et al. 2019;Srivaro et al. 2019) but very little was reported on treated tropical hardwoods (Shukla et al. 2019;Lim et al. 2020;Qin et al. 2019). Limited studies have been found on determining the bonding of wood treated with ACQ or CA-B. ...
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The objective of this study is to determine the effects of alkaline copper quaternary (ACQ) treatment on the surface quality and bonding performance of four Malaysian hardwood species, namely batai, sesenduk, rubberwood and kedondong. The samples were impregnated with 2% ACQ preservatives and bonded with phenol-resorcinol–formaldehyde resin for cross laminated timber (CLT) fabrication. The changes in density and the retention of both ACQ and copper after the treatment were recorded. Surface roughness and wettability of both treated and untreated samples were measured. Block shear and delamination tests were performed to evaluate the bond-line strength of CLT. The study revealed that the average surface roughness (Ra) of each species increased significantly. Wettability of batai, sesenduk, rubberwood and kedondong was significantly higher than that of the untreated samples suggesting an improvement in surface wettability. For single-species CLT, treated rubberwood has the highest shear strength followed by kedondong, sesenduk and batai with values of 9.53 N/mm2, 6.00 N/mm2, 5.68 N/mm2 and 4.19 N/mm2, respectively. While for mixed-species CLT, the combination of ACQ-treated rubberwood-sesenduk-rubberwood has the highest block shear strength with a value of 8.05 N/mm2. No delamination was observed from all samples. ACQ treatment was found to not affect the block shear strength significantly. Therefore, ACQ preservatives can be used to produce CLT with good bonding performance.
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This paper presents a pilot study on bending and shear strength of glued laminated (glulam) timber using selected tropical timber namely, Kekatong (Cynometra spp.) and Melagangai (Potoxylon melagangai) as an alternative for timber railway sleepers. Selected timbers were manufactured in accordance with MS758:2001 and the bending test was conducted according to ASTM D198:2013. The shear test for glue line integrity was performed to observe the bond performance in glulam accordance to MS758:2001.The results showed both species can be used as structural members since the bending strength obtained from the laboratory work is greater than the allowable bending strength. In terms of the percentage of wood failure, the bonding characteristics of both glulam satisfied the bonding requirement stipulated in the standard and have the potential to be used as glulam timber railway sleepers.
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Sugi (Japanese cedar: Cryptomeria japonica) is the most important afforestation species in Japan. Its growing stock has been increasing year by year. Thus, development of new wood products made of sugi has been a national priority for more than two decades. Development of sugi structural glued laminated timber (glulam) was one of the responses to this push. However, in the 1990s, the Japanese glued laminated timber (GLT) industry did not accept sugi as a raw material for glulam, because several problems existed in the wood quality of sugi such as lower strength properties than those of the major imported species. This drawback spurred intensive research on sugi glulam in Japan. The results contributed to the significant revision of the Japanese Agricultural Standard (JAS) for GLT in 2008. The standard permitted the use of various new laminae and products such as a sugi composite GLT beams using different species of laminae with high modulus of elasticity. Although fireproof GLT is not part of the existing JAS for GLT, several fireproof laminated products with 1-h fireproofing performance have been developed since the Japanese Building Standards Law was revised in 2000.
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The aim of this study was to determine the physical and mechanical properties of glued laminated timber (glulam) manufactured from small-diameter logs of three wood species, Acacia mangium (mangium), Maesopsis eminii (manii), and Falcataria moluccana (sengon), with densities of 533, 392, and 271 kg/m3, respectively. Glulam measuring 5 cm by 7 cm by 160 cm in thickness, width, and length, respectively, was made with three to five lamina, or layers, and isocyanate adhesive. The glulams contained either the same wood species for all layers or a combination of mangium face and back layers with a core layer of manii or sengon. Solid wood samples of the same size for all three species were included as a basis for comparison. Physical-mechanical properties and delamination tests of glulam referred to JAS 234:2003. The results showed that the properties of same species glulam did not differ from those of solid wood, with the exception of the shear strength of glulam being lower than that of solid wood. Wood species affected glulam properties, but three- and five-layer glulams were not different except for the modulus of elasticity. All glulams were resistant to delamination by immersion in both cold and boiling water. The glulams that successfully met the JAS standard were three- and five-layer mangium, five-layer manii, and five-layer mangium-manii glulams.
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This study established a prediction model for bending properties of glued-laminated timber (glulam) using optimized knot and modulus of elasticity (MOE) distributions of lumber laminate as the main input variables. For this purpose, knot and MOE data were investigated for all pieces of lumber that were prepared for glulam manufacturing, and statistical distributions of knot size, knot number in one lumber, and MOE of each laminate were optimized as distribution functions. These knot and MOE data were used as input variables in the prediction model for bending properties, and were also used in generating virtual glulam using the inverse transform method. Prediction of bending properties for glulam was carried out using the transformed section method, which is partially provided in ASTM D 3737 (Annex A4). Predicted values were compared with those from full-scale four-point bending tests for 60 six-layered glulams with 10 different laminar combinations. Finally, the allowable bending properties of glulam for each specific laminate combination were determined by calculating the fifth percentile of the modulus of rupture and the average modulus of elasticity from virtual test results of more than 1000 virtual glulams. From the results of this study, predicted bending properties for glulam and their distributions could be used for structural design in both allowable stress design and limit state design.
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This paper presents test evaluation results for red maple structural glued-laminated (glulam) beams manufactured from two different lumber resources. Two types of red maple glulam beam combinations were evaluated: 1) a glulam combination designed with E-rated lumber in 25 percent of the outer laminations (top and bottom) and visually graded lumber in 50 percent of the center laminations; and 2) a wide-width glulam combination with laminations made from nominal 2- by 4- and 2- by 6-inch No. 2 grade lumber laid edge-to-edge having staggered end joints (termed 2 by 4/2 by 6 glulam combination). The two research studies differed in that one study obtained red maple lumber using common sawing practices used for appearance hardwood lumber recovery, whereas the other study exclusively obtained lumber from the red maple log cants that had been processed for removal of furniture-grade material. Given these two lumber resources, the test results from the two studies showed that it was feasible to develop structural glulam combinations made from E-rated lumber that would meet or exceed a target design bending stress of 2,400 psi and a target modulus of elasticity (MOE) of 1.8 × 106 psi. In addition, the 2 by 4/2 by 6 glulam combination exceeded published design stresses for vertically laminated bending strength, MOE in both the horizontally and vertically laminated orientations, and horizontal shear stress in the vertically laminated orientation. Based on the results of the 2 by 4/2 by 6 glulam combination, it was determined that edge gluing the laminations to form wide-width lumber is not required to achieve targeted strength and stiffness levels. Data analysis showed that ASTM D 3737 procedures developed for softwood species accurately predict beam stiffness and provide conservative bending and horizontal shear strength estimates for red maple glulam beams. Also, it was shown that results from ASTM D 143 shear-block tests could be used to accurately predict horizontal shear strength of 2 by 4/2 by 6 red maple glulam beams.
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This study presents properties test results of glued-laminated (glulam) beams made from two fast growing tree species, namely African wood ( Maesopsis eminii ) and mangium ( Acacia mangium ) using water based polymer isocyanate (WBPI) as a binder. Laminations were used consist of 2, 4, 6, 8 and 12 cm in widthnesses, 2 cm in thickness and 260 cm in length. Each lamination was graded using Machine Stress Grading (namely by Panter or plank sorter) to determine its Modulus of Elasticity (MOE). Cross-section of five types of glulam beams was 6x12 cm, arranged of various widths and based on MOE of laminations. The study results describe that glulam beams made from mangium showed better performance compared to those of African wood based on values of MOE and Modulus of Rupture (MOR). In general, results showed that almost all of glulam beams types of both wood species fulfill the JAS 234:2003 standard in moisture content, MOE, MOR, shear strength and immersion delamination test. However, performance of glulam beams was unsatisfactory in wood failure ratio and boiling water soak delamination test.
Malaysian government has already built the first glulam structure in Malaysia with the aim of demonstrating the potentialities of using indigenous hardwood timber for glulam. Since Malaysia possesses a vast variety of timber species, hence there is a need to identify suitable species for glulam manufacturing. This paper presents the bending performance of Malaysian hardwood glulam beams, manufactured from different categories namely heavy, medium and light hardwood timbers. A series of tests were carried out on the glulam beam that includes bending test, delamination test and shear test of glue line. Results in this study will be useful to manufacturers interested in using Malaysian hardwood for glulam beams.
Existing lamination and beam test results were analytically reviewed to quantify the laminating effect for European and North American glued-laminated (glulam) timber. The laminating effect is defined as the increase in strength of lumber laminations when bonded in a glulam beam compared with their strength when tested by standard test procedures. Fundamental concepts are presented to define the laminating effect, estimates are made of its magnitude, and relationships are presented to describe its character. Our review of experimental data indicated that the laminating effect ranged from 1.06 to 1.59 for European glulam and from 0.95 to 2.51 for North American glulam.
The authors investigated the properties of small-sized joint-free laminated beams (80mm in width, 115mm in height and 2m in length) composed of 7 mechanically graded laminations of poplar (Populus x euramericana, 'Neva' clone) and eucalyptus (Eucalyptus grandis, '7', '329', '330' and '358' clones) in different combinations. Tests were carried out in order to determine their modulus of elasticity, bending strength and shear modulus; the bonding reliability was also evaluated by means of delamination and shear tests in the glue lines. The beams composed using the '330' eucalyptus clone, by its own or in combination with poplar, showed outstanding mechanical performance and the best structural efficiency. In addition the bonding quality, also at the interface between the two species, proved to be excellent. The results, separately for each clone of E. grandis, in terms of absolute values and structural efficiency, are shown and discussed.Die Autoren untersuchten die Eigenschaften von kleinen verbindungsfreien Brettschichttrgern (von 80mm Breite, 115mm in Hhe and 2m Hhe) zusammengesetzt aus 7 mechanisch sortierten Brettschichthlzern von Pappel (Populus x euramericana, 'Neva' clone) und Eucalyptus (Eucalyptus grandis, '7', '329', '330' und '358' Klonen) in unterschiedlichen Kombinationen. Tests wurden durchgefhrt, um ihr Elastizittsmodul, ihre Biegefestigkeit und Scherfestigkeit zu bestimmen; die Haftverllichkeit wurde ebenfalls abgeschtzt durch Delaminierung und Schertests in den Klebefugen. Die zusammengestellten Balken, bei denen man den 330 Eukalyptusklon verwendete, entweder allein oder in Kombination mit Pappel, zeigten herausragende mechanische Qualitt und die beste strukturelle Leistungsfhigkeit. Zustzlich erwies sich die Bindefestigkeit, auch an den Grenzflchen zwischen den beiden Arten als exzellent. Es werden die Ergebnisse separat fr jeden Klon von E. grandis, als absolute Werte und als strukturelle Leistungsfhigkeit dargestellt und diskutiert.