Conference PaperPDF Available

Evaluation of the Structural Behaviour of Beam-beam Connection Systems using Compressed Wood Dowels and Plates

Authors:

Abstract and Figures

To support the transition to a bio-based society, it is preferable to substitute metallic fasteners and adhesives in timber construction with an eco-friendly alternative. Recent studies have identified compressed wood dowels and plates as a possible substitute for metallic fasteners in contemporary and mainstream applications. In this study, a spliced beam-beam connection system using compressed wood dowels and slotted-in compressed wood plates was examined under four-point bending. The study has considered specimens with compressed wood dowels of 10 mm diameter and compressed wood plates of 10 mm thickness. The load carrying capacity of connections using compressed wood dowels and plates were compared to connections utilising steel dowels and plates of equivalent capacity. Typical failure modes, moment resistance and rotational stiffness of both connection systems are evaluated on the basis of the experimental results. Tests have demonstrated similar failure modes when comparing steel-timber and compressed wood-timber connection systems. The mean failure load for the compressed wood-timber connection system is only 20.3% less than that achieved for the steel-timber connection system. The mean rotational stiffness of the compressed wood-timber connection system is 18.55% less than that achieved for the steel-timber connection system. These preliminary results demonstrate the potential for the use of compressed wood elements in the manufacture of timber connections.
Content may be subject to copyright.
EVALUATION OF THE STRUCTURAL BEHAVIOUR OF BEAM-BEAM
CONNECTION SYSTEMS USING COMPRESSED WOOD DOWELS AND
PLATES
Sameer Mehra1, Conan O’Ceallaigh1, Fatemeh Hamid - Lakzaeian1, Zhongwei Guan2,
Adeayo Sotayo2, Annette M. Harte1
ABSTRACT: To support the transition to a bio-based society, it is preferable to substitute metallic fasteners and
adhesives in timber construction with an eco-friendly alternative. Recent studies have identified compressed wood dowels
and plates as a possible substitute for metallic fasteners in contemporary and mainstream applications. In this study, a
spliced beam-beam connection system using compressed wood dowels and slotted-in compressed wood plates was
examined under four-point bending. The study has considered specimens with compressed wood dowels of 10 mm
diameter and compressed wood plates of 10 mm thickness. The load carrying capacity of connections using compressed
wood dowels and plates were compared to connections utilising steel dowels and plates of equivalent capacity. Typical
failure modes, moment resistance and rotational stiffness of both connection systems are evaluated on the basis of the
experimental results. Tests have demonstrated similar failure modes when comparing steel-timber and compressed wood-
timber connection systems. The mean failure load for the compressed wood-timber connection system is only 20.3% less
than that achieved for the steel-timber connection system. The mean rotational stiffness of the compressed wood-timber
connection system is 18.55% less than that achieved for the steel-timber connection system. These preliminary results
demonstrate the potential for the use of compressed wood elements in the manufacture of timber connections.
KEYWORDS: Connections, compressed wood dowels, compressed wood plates, four-point bending
1 INTRODUCTION
123
The widespread use of metallic fasteners and adhesives in
modern timber construction has negative implications for
the end-of-life disposal or re-use of the structural timber
components. Emission of volatile organic compounds
during manufacture of synthetic adhesives may have
human health impacts in addition to the environmental
impact. To cope with the upcoming transition to a bio-
based society, it is preferable to substitute metallic
fasteners and adhesives with an eco-friendly alternative
such as wood-based connectors.
The use of wood-based connectors is not new. In some of
the early Egyptian and Polynesian boats, wooden pegs
and treenails were used to fasten together the various
pieces of the hull [1]. Treenails or trunnels have also been
used as connectors in timber frame and covered bridge
constructions [2]. Dense hardwood has traditionally been
used for connectors in timber structures. However, the use
of hardwood fasteners is limited by resource availability
and the fact that hardwood connectors undergo stress
relaxation, which causes loosening of the joint over time
necessitating regular tightening [3-4].
The mechanical and physical properties of underutilised
softwood species can be easily modified by chemical and
1
Sameer Mehra, National University of Ireland Galway,
Ireland, s.mehra1@nuigalway.ie
1Conan O’Ceallaigh, National University of Ireland Galway,
Ireland, conan.oceallaigh@nuigalway.ie
1Fatemeh Hamid-Lakzaeian, National University of Ireland
Galway, Ireland, fatemeh.hamid@nuigalway.ie
thermal treatments. In recent years, densification of wood
by compression, thermal and chemical treatments has
been the subject of several research programmes.
Examples include viscoelastic thermal compression
wood, thermo-hydro-mechanical densified wood, oil-
heated treatment and acetylated wood.
Compression of wood results in increased density,
decreased porosity and improved material strength,
stiffness, hardness and dimensional stability [5].
Compressed Sitka spruce (Picea sitchensis) has shown
increased Young’s modulus with increasing compression
ratio in bending [6]. Compressed wood (CW) of Japanese
cedar was used as a substitute for high density hardwood
for making shear dowels [7]. When compressed radially,
Japanese cedar has been shown to have good properties as
a dowel material in terms of its enhanced strength and
ductility [7].
CW friction joints were found to have a satisfactory high
initial stiffness, load carrying capacity and ductility,
where compressed wooden wedges were used together
with a conventional bolt-and-bearing-plate joint [8]. Jung
et al. [9] demonstrated that large moment resistance and
ductility can be achieved in column-beam joints utilising
CW plates and dowels. The high embedding performance
2 Zhongwei Guan, University of Liverpool, United Kingdom,
zhongwei.guan@liverpool.ac.uk
2Adeayo Sotayo, University of Liverpool, United Kingdom,
a.sotayo@liverpool.ac.uk
1Annette M. Harte, National University of Ireland Galway,
Ireland, annette.harte@nuigalway.ie
of the CW plates contributed to the rotational stiffness,
and the high shearing performance of the CW dowels to
the axial stiffness.
Current deign codes do not adequately address the design
of timber connections using wood-based connectors. The
objective of this study is to investigate feasibility of CW
dowels and CW plates as eco-friendly substitutes of
metallic fasteners in moment-resisting connections. The
study comprises experimental evaluation of CW and steel
beam-beam moment connections to the determine typical
failure modes, load carrying capacity and moment
resistance.
2 EXPERIMENTAL STUDY
2.1 INTRODUCTION
This study investigates the use of CW dowels and plates
in beam-beam moment connections and compares them to
similarly loaded moment connections utilising steel
dowels and plates. The beam-beam moment connection
between two glued laminated beams is illustrated in
Figure 1. The beams are spliced together using a total of
two plates and twenty dowels.
Figure 1: Beam-beam moment connection
2.2 MATERIALS
A total of four test specimens were produced comprising
two replications of a steel fastened connection system and
two of a compressed wood fastened connection system.
The dimension lumber used in this study was Irish-grown
Douglas Fir (Pseudotsuga menziesii). There were eight
glulam beams manufactured. In order to minimise the
variability among the glulam beams, timber laminates
were selected based upon their density. The mean density
of the laminates was 477.74 kg/m3 with a standard
deviation of 4.74. Each beam consisted three laminates of
1575 mm long and 52.5 mm thick. The cross-section area
of each beam was 115 mm x 157.5 mm. The laminates
were glued together using a one-component PU adhesive
and were clamped in a rig to a minimum pressure of 0.6
MPa in accordance with EN 14080 [10]. All the beams
were conditioned at a temperature of 20 ± 2˚C temperature
and 65 ± 5 % relative humidity prior to testing.
The CW plates were manufactured using Scots Pine
(Pinus sylvestris) wood compressed in the radial direction
with a compression ratio of approximately 54% at the
University of Liverpool, United Kingdom. The CW
dowels were similarly compressed in the radial direction.
A schematic of manufacturing process and the finished
dowels are presented in Figure 2a and Figure 2b,
respectively. The final density of the compressed wood
dowels ranged from 1100-1500 kg/m3 with the diameter
of 10 + 0.5 mm.
Each glulam beam in the test programme was routed at
one end to accommodate two compressed wood or steel
plates of 10 mm thickness. The routed slot was 11 mm in
width. The grade of steel used in this study for plates and
dowels was S275. The steel plates dimensions were 480 x
152 mm2 and the compressed wood plates dimensions
were 480 x 157.5 mm2.
Figure 2: Compressed wood fasteners, (a) Schematic of
manufacturing of compressed wood plates and dowels, (b)
finished compressed wood plates and dowels
2.3 PRELIMINARY DESIGN OF CONNECTION
SYSTEM
To assess the performance of CW fastened connections,
beam-beam connections using equivalent capacity steel
dowels and steel plates were produced as control
specimens.
The Eurocode 5 does not adequately address the
guidelines for designing of moment resisting dowel type
connections. Thus, the recommendation for the minimum
spacing criteria for both timber to steel and timber to
timber moment resisting connection were followed as per
the guidelines by Porteous and Kermani [11]. The
possible failure modes under consideration for the steel-
timber connection are illustrated in Figure 3 as defined in
Eurocode 5 [12].
(1) (2) (3)
Figure 3: Failure modes for steel-timber connection (Porteous
and Kermani [11])
The corresponding characteristic load carrying capacity
per steel dowel per shear plane for each steel-timber
connection failure mode is calculated using Equations (1)-
(3).
 
(1)
(a)
where:
Fv,Rk = Characteristic load carrying capacity of per steel
dowel per shear plane
t1 = Timber board thickness
fh,1,k = Embedment strength
My,Rk= Yield moment of fastener
Fax,Rk = Withdrawal capacity of fastener.
The load carrying capacity of the CW-timber connection
is calculated based on failure modes illustrated in Figure
4. The timber-timber connection has one more failure
modes compared to the timber-steel connection.
(4) (5) (6) (7)
Figure 4: Failure modes for the timber-timber connection [11]
The corresponding characteristic load carrying capacity
per CW dowel per shear plane for each failure mode is
calculated using Equation (4)-(7).
where,
fh,2,k = Embedment strength of central timber element
t2 = timber board thickness of the central timber element
β = The ratio between the embedment strength of
connected members
and the rest are as described previously.
The yield moment of the steel dowel was calculated as per
Eurocode 5 [12]. The characteristic yield moment (My,RK)
of the steel dowel was 27,412 N-mm. Whereas the
characteristic yield moment of the compressed wood
dowel was calculated from experimental three point
bending tests in accordance with ASTM 1575 [13]. The
characteristic yield moment (My,Rk) of the compressed
wood dowels was 13.151 N-mm.
The assumed characteristic embedment strength of the
compressed wood plate was 125.80 (N/mm2) as reported
by Jung et al. [7]. Whereas the embedment strength of the
glulam was calculated as per Eurocode 5 [12]. Since the
embedment strength is the function of the diameter and
characteristic density of the material. Therefore, the
embedment strength of glulam beam for a steel dowel of
8 mm diameter is 31 N/mm2 and for a compressed wood
dowel of 10 mm is 31.68 N/mm2.
The failure mode is that associated with the minimum
value from each set of equations, which is the
characteristic load carrying capacity per fastener per shear
plane. The connection parameters and calculated
theoretical moment resistance of both connection systems
are tabulated in Table 1.
Table 1: Theoretical moment resistance of both steel-timber
beam and compressed wood-timber beam connection systems
2.4 FABRICATION OF CONNECTION SYSTEM
The fabrication of the beam-beam spliced connection
system can be seen in Figure 5. In Figure 5a, the beams
are fixed in position using clamps while the CW plates are
positioned prior to dowel insertion. Once aligned, the
dowels were driven into rectangular pattern to form the
connection.
Figure 5: Spliced connection system, (a) fabrication process, (b)
plan view of steel and compressed wood connection system.
In Figure 5b, the completed timber-steel connection and
the timber-timber connection systems can be seen. The
designed spacing edge and end distances are summarised
in Table 2.
 

(2)
 
(3)
 
(4)
 
(5)


 
(6)
 

(7)
Design Parameter
Steel-timber
connection
Compressed
wood-timber
connection
Dowel diameter
8
10
No. of dowels
10
10
No. of plates
2
2
Design moment
capacity of glulam
5.48 kN-m
5.48 kN-m
Design Moment
capacity of the
connection
3.03 kN-m
2.90 kN-m
(a)
b)
(b)
Table 2: Spacing, edge and end distances for designed
connection system
Spacing, edge and end distances
Spacing (mm)
Spacing
Parallel to grain
36
Spacing
Perpendicular to grain
36
End
Loaded end
63.5
End
Unloaded end
63.5
Edge
Loaded edge
42.5
Edge
Unloaded
42.5
2.5 STRUCTURAL TESTING
The structural tests were conducted at the laboratory of
Timber Engineering Research Group (TERG) at the
National University of Ireland Galway. The beam
specimens were tested in flexure over a simply supported
span in four-point bending in accordance with EN 408
[14]. Figure 6 illustrates the beam-beam connection test
set-up with the spliced connection at mid-span. As
recommended by Wang et al. [15], a gap of 10 mm was
used to avoid friction between the beams. Simple lateral
supports were placed at the end of the beams to avoid
lateral movement. This ensures that the connection was
subject to a pure bending load. The testing set up is
illustrated in Figure 7.
Figure 7: Four-point bending test set up
The continuous load was applied at the rate of 0.15
mm/second using a Dartec 500 kN Servo hydraulic testing
machine. The vertical displacement at the mid-span of the
connection was measured by a micro-epsilon
optoNCDT1420 laser with an accuracy of 8µm. Two
linear variable differential transformers (LVDTs), Δ1 and
Δ2 were placed at a fixed spacing of 300 mm on one side
of the connection as illustrated in Figure 6.
The respective movement of the LVDTs allowed the
rotation angle (θ) of the connection to be calculated by
1-Δ2)/300. Each connection system was initially
preloaded up to 40% of maximum load and unloaded in
accordance with EN 408 [14]. The vertical load was
continuously applied until significant failure took place.
Each specimen failed within 300 ± 120 seconds of
commencing the test in accordance with EN408 [14]. The
flexural stiffness, rotational stiffness, maximum failure
load and maximum bending moment of the connections
were determined.
3 TEST RESULTS
3.1 TYPICAL FAILURE MODES
Initially, when the vertical load is applied, the connection
at mid-span begins to rotate and the beams began to move
closer to each other at the top of the connected beams and
begin to move apart at the bottom of the connection. The
10 mm gap at the splice connection ensured no additional
friction or embedment effects occurred at this point.
Loading continued until tension splitting took place along
the bottom row of one of the connected ends. The tension
splitting initiated at dowel number 1 as illustrated Figure
8. With increasing load, splitting propagated along the
bottom row of the connection. The same failure mode was
also observed in the connection systems fabricated using
steel fasteners.
Figure 8: Typical failure modes (a) Connection system using
compressed wood fasteners (b) Connection system using steel
fasteners
(a)
(b)
Figure 6: Configuration of test set up for four-point bending as per EN408
3.2 LOAD-DISPLACEMENT RESPONSE
In Figure 9, the load-displacement behaviour of the beam-
beam connections can be seen. The behaviour can be seen
to be linear elastic until failure when the splitting on the
timber beam occurs. Additional capacity can be seen after
the initial failure of dowel number 1 as presented in Figure
8.
Figure 9: Load v/s displacement curve for both the connection
systems: steel and compressed wood.
The steel-timber beam connections achieved a greater
overall load carrying capacity than that of the CW timber-
timber beam connection. The maximum load carrying
capacity of each connection is tabulated in Table 3.
Table 3: Maximum load carrying capacity of steel-timber beam
connection and the CW-beam connection
Connection ID
Maximum load
(kN)
Steel connection 1
9.8
Steel connection 2
11.8
CW connection 1
8.1
CW connection 2
9.2
As shown in Table 4, the mean failure load of 10.8 kN
was achieved for the steel-timber beam connections and
the mean failure load of 8.6 kN was achieved for the CW
timber-timber beam connections. The is an overall
percentage decrease of 20.3% for the CW dowel
connection.
Table 4: Mean failure load of the steel-timber beam connection
and the CW-timber beam connection.
Connection
type
Mean failure
load (kN)
Steel-timber
10.8
CW-timber
8.6
3.3 BENDING STIFFNESS
The mean bending stiffness results of the spliced beams,
calculated in accordance with EN 408 [14]. As observed
in Figure 9, both the CW timber-timber and steel-timber
connection systems behave in a linear elastic manner until
brittle failure. The bending stiffness results for spliced
beams are presented in Table 5 and the mean results are
presented graphically in Figure 10.
Table 5: Bending Stiffness of the spliced beams
Connection ID
Bending Stiffness
(Nmm2)
Steel connection 1
1.38x1011
Steel connection 2
1.08x1011
CW connection 1
0.68x1011
CW connection 2
0.83x1011
The bending stiffness of the beams is greater for the steel-
timber beam connections. The percentage decrease in
mean stiffness between the steel-timber beam connections
and the CW timber-timber beam connections is 38%. This
is a promising result for the CW system. Further planned
testing will examine this initial finding.
Figure 10: Mean bending stiffness results of steel-timber
connected beams and the CW-timber connected beams
3.4 MOMENT RESISTANCE
Usually, multiple-fastener connections often fail in
splitting mechanism due to non-uniform load distribution
and the concentration of stress around the fastener’s hole
[16]. Figure 9 validates the brittle failure of the designed
connection systems. The maximum moment of each
connection specimen was calculated based on the peak
point of the moment vs rotation curves. The maximum
moment capacity of the tested connection systems can be
seen in Table 6. The steel-timber connections achieved a
greater moment capacity when compared to the CW
timber-timber connections.
0
2000
4000
6000
8000
10000
12000
0 20 40 60 80 100
Load (N)
Displacment (mm)
Steel Connection 1
Steel Connection 2
CW connection 1
CW connection 2
0
2E+10
4E+10
6E+10
8E+10
1E+11
1.2E+11
1.4E+11
Steel-timber Connected Beams CW-timber Connected Beams
Bending stiffness (Nmm2)
Table 6: Moment resistance (kN.m) for both the connection
systems:
Connection ID
Maximum
Moment (kN.m)
Steel connection 1
9.28
Steel connection 2
11.17
CW connection 1
7.63
CW connection 2
8.67
The mean maximum moment for both the connection
systems were tabulated below in Table 7.
Table 7: Mean maximum moment capacity for both connection
systems
Connection
type
Maximum
Moment (kN.m)
Steel-timber
10.2
CW-timber
8.1
The mean maximum moment of the steel-timber
connection was 10.2 kN.m and the mean maximum
moment of the CW timber-timber connection was 8.1
Kn.m. This represents a percentage increase of 20.5%.
The mean values presented are greater than the design
values tabulated in Table 1.
3.5 MOMENT-ROTATIONAL ANGLE
The bending moment (M) and corresponding rotational
angles (θ) were calculated based on the load and
displacement measured from load cell and displacement
transducers, respectively. Figure 11 illustrates the M-θ
relationship for both the steel and compressed wood
connection systems until the first point of failure as seen
in Figure 9.
Figure 11: Moment v/s rotational angle curve for both the
connection systems: steel and compressed wood
The initial rotational stiffness for both the connection
systems, calculated based on 20% and 40% of the
maximum moment and corresponding rotational angle
[17]. The initial rotational stiffness of both the connection
systems were summarised in Table 8.
Table 8: Initial rotational stiffness (kN.m/rad) of steel-timber
beam connections and CW-timber beam connections
Connection ID
Initial rotational
stiffness (kN.m/rad)
Steel connection 1
548.5
Steel connection 2
966.3
CW connection 1
630.2
CW connection 2
603.6
Table 9: Mean initial rotational stiffness of both the steel-timber
and CW-timber connection
Connection
type
Initial rotational
stiffness (kN.m/rad)
Steel-timber
757.4
CW-timber
616.9
At the failure moment in Figure 11, the compressed wood-
timber connections have shown greater connection
rotation when compared to steel-timber connection. The
mean initial rotational stiffness of the steel timber is
18.55% higher than that of CW-timber connection. This
is as expected due to the lower stiffness of the CW-timber
connection.
Future tests will further examine the moment capacity and
rotational angle of such connections. The connections in
this test failed due to splitting of the timber along the
bottom row and there was no ductility observed in the
connection. In an attempt to increase the connection
ductility, future tests on spliced beams utilising a reduced
number of fasteners and greater fastener spacing will be
examined.
4 CONCLUSIONS
The bending test results delivered insights into the effects
of CW dowels and plate configurations on the load
carrying capacity, bending stiffness, maximum moment
capacity and rotational stiffness of the connection system.
The performance compared favourably with the
equivalent steel connections. The results obtained have
substantiated CW fasteners as potential green alternative
to adhesives and metallic fasteners.
Tests have demonstrated similar failure modes when
comparing steel-timber and CW timber-timber
connection systems. The mean performance of the CW-
timber connection is less than that of the steel-timber
connection system, when comparing ultimate failure load,
bending stiffness, moment carrying capacity and
rotational stiffness however this is to be expected due to
the mechanical properties of the CW elements compared
to that of steel. The mean failure load for CW-timber
connection is only 20.3% less than that achieved for the
steel-timber connections. The mean rotational stiffness of
CW-timber connection is 18.55% less than that achieved
for the steel-timber connections. These preliminary
results demonstrate the potential for the use of CW
elements in the manufacture of timber connections.
Both connection systems demonstrated brittle failure.
Further testing is proposed to induce ductile failure and to
understand the effect of connection geometry, dowel
0 0.2 0.4 0.6 0.8 1
0
1
2
3
4
5
6
7
8
9
10
Rotation Angle (˚)
Moment Capcity (kN.m)
Steel Connection 1
Steel Connection 2
CW Connection 1
CW Connection 2
diameter, number of dowels, spacing of dowels, number
and spacing of CW plates.
5 FUTURE WORK
Eurocode 5 is the current harmonised design standard for
timber structures in Europe. Currently, there are no rules
governing the use of timber-timber connections and by
extension, timber-timber connections utilising CW
elements. The current equations for the lateral load
carrying capacity of fasteners in Eurocode 5 are known as
the Johansen equations. Such equations can be modified
to allow the use of hardwood and CW timber fasteners.
Additional equations must be considered to utilise CW
plate elements within such connection systems. As a
result, a series of material characterisation tests are
proposed to establish be properties of CW fasteners and
CW plates. To utilise CW fasteners, the bending moment
capacity, must the established. To utilise CW plates, the
embedment strength must be considered, and this must be
examined parallel and perpendicular to the grain for use
in moment resisting connections.
The tests performed on connections utilising CW
fasteners and plates may then be compared to design
values from Eurocode 5. The current Eurocode values for
CW connections, presented in Table 1, are based on a
small number of tests on CW dowels and assumed
properties of CW plates sourced within the literature.
While the mean experimental test results are in excess of
the calculated Eurocode design values, further testing is
required to allow for comparisons to characteristic values.
ACKNOWLEDGEMENT
The study had been conducted within the framework of
project “Towards Adhesive Free Timber Buildings -
AFTB” at the College of Engineering and Informatics,
National University of Ireland Galway, Ireland. The
AFTB project is funded by Interreg North West Europe
via the European Regional Development Fund (ERDF).
REFERENCES
[1] E.P. Suter, An historical study of wood fasteners
used in wood work. M.Sc. Thesis, North Texas
State College Jonesboro, Texas, 1953.
[2] J.D. Edwards, N. Verton, A Creole Lexicon
Architecture, Landscape, People, Louisiana State
University Press, Baton Rouge, 2004.
[3] K. Tanaka, Y. Demoto, J. Ouchi, M. Inoue,
Strength property of densified Sugi adopted as
material of connector, in: Proceedings of the
World Conference on Timber Engineering
(WCTE), Trentino (Italy), 2010.
[4] Z. Guan, K. Komatsu, K. Jung, A. Kitamori,
Structural Characteristics of Beam - Column
Connections Using Compressed Wood Dowels
and Plates, in: Proceedings of the World
Conference on Timber Engineering (WCTE),
Trentino (Italy), 2010.
[5] M. Riggio, J. Sandak, A. Sandak, Densified
wooden nails for new timber assemblies and
restoration works: A pilot research, Construction
and Building Materials. 102 (2016) 10841092.
doi:10.1016/j.conbuildmat.2015.06.045.
[6] H. Yoshihara, S. Tsunematsu, Bending and shear
properties of compressed Sitka spruce, Wood
Science and Technology. 41 (2007) 117131.
doi:10.1007/s00226-006-0091-8.
[7] K. Jung, A. Kitamori, K. Komatsu, Evaluation on
structural performance of compressed wood as
shear dowel, Holzforschung. 62 (2008) 461467.
doi:10.1515/HF.2008.073.
[8] A. Kitamori, K. Jung, K. Komatsu, Utilization of
Compressed Wood As Mechanical Fastenrs of
Friction Joints in, in: 11th International
Conference on Non-Conventional Materials and
Technologies, NOCMAT, University of Bath,
UK, 2009.
[9] K. Jung, A. Kitamori, K. Komatsu, Development
of a joint system using a compressed wooden
fastener II: Evaluation of rotation performance for
a column-beam joint, Journal of Wood Science.
56 (2010) 118126. doi:10.1007/s10086-009-
1078-5.
[10] CEN, EN 14080. Timber structures - Glued
laminated timber and glued solid timber -
Requirements, Comité Européen de
Normalisation, Brussels, Belgium, 2013.
[11] J. Porteous, A. Kermani, Structural Timber
Design to Eurocode 5, Blackwell Publishing,
2007.
[12] CEN, EN 1995-1-1. Eurocode 5: Design of timber
structures - Part 1-1: General - Common rules and
rules for buildings, Comité Européen de
Normalisation, Brussels, Belgium, 2009.
[13] ASTM, ASTM 1575-17. Standard Test Method
for Determining Bending Yield Moment of Nails
1, Test. i (2017) 25. doi:10.1520/F1575-03R13.
[14] CEN, EN 408. Timber structures - Structural
timber and glued laminated timber -
Determination of some physical and mechanical
properties, 44 (2012).
[15] M. Wang, X. Song, X. Gu, Y. Wu, Mechanical
Behavior of Bolted Glulam Beam-To-Column
Connections With Slotted-in Steel Plates Under
Pure Bending, in: Proceedings of the World
Conference on Timber Engineering (WCTE),
(Vienna) Austria, 2016.
[16] A. Awaludin, T. Hayashikawa, Predicting
moment capacity of multiple-bolt timber
connection through splitting mechanism,
Materials, Experimentation, Maintenance and
Rehabilitation - Proceedings of the 10th East
Asia-Pacific Conference on Structural
Engineering and Construction, EASEC 2010.
(2006).
[17] C.P. Heine, Simulated Response of Degrading
Hysteretic Joints With Slack Behavior. PhD
Thesis, Viriginia Polytechnic Insitute and State
University, 2001.
... The densified wood used in this study was produced by thermo-mechanical compression of softwood timber (Scots pine -Pinus sylvestris) to increase its density, strength, stiffness and hardness (Mehra et al., 2019(Mehra et al., , 2018 making it highly suited to demanding applications. ...
... The mould was then subjected to a pressure compressing the radial dimension of the timber and forming a 10 mm diameter dowel when the mould is fully closed. The densified timber dowels were then cooled under pressure until the temperature was less than 66° C (Mehra et al., 2018). This resulted in a final mean density ranging between 1100-1500 kg/m 3 . ...
... where F b,Rk is the buckling capacity of the densified wood dowel, n is the number of densified wood dowels and the other terms are as previously described. The densified wood dowel properties in the parallel to the grain direction used in this study are based on experimental results presented by Mehra et al. (2018). Figure 11 shows a comparison between the characteristic design results and the recorded results from testing of the specimens reinforced with densified wood dowels. ...
Article
Full-text available
An investigation was carried out to examine the potential to utilise densified wood dowels as a reinforcement for timber subjected to compression loading perpendicular to the grain. While timber has a high strength-to-weight ratio parallel to the grain, it demonstrates poor strength perpendicular to the grain and in recent years there has been a significant number of studies examining the use of steel screws and bonded-in rods as reinforcement in this area. This is becoming more and more important with the increased use of timber in medium-to-high rise structures. In this study, thermo-mechanical densified wood in the form of dowels are utilised as compression reinforcement perpendicular to the grain and tested to failure. Thermo-mechanically densified dowel reinforcement arrangements of 2, 4, and 6 dowels are examined experimentally under a compressive load and compared to timber samples similarly reinforced but with steel self-tapping screws. The results have demonstrated the potential to utilised densified wood to create an all-wood solution to reinforce against compressive stresses perpendicular to the grain. Additionally, modifications to recently proposed Eurocode 5 recommendations for the design of compression reinforcement using self-tapping steel screws are presented, which are suitable for the design of compression reinforcement using densified wood dowels.
... In recent years, there has been a significant number of studies that have examined the benefits of using modified wood in structural applications [1][2][3][4][5][6]. The potential to use modified wood as a replacement for typical metallic connections using steel plates and steel fasteners was examined by Mehra et al. [7]. Mehra et al. [7] experimentally tested a series of spliced beam-beam connections utilising compressed wood (CW) material in the form of dowels and plates. ...
... The potential to use modified wood as a replacement for typical metallic connections using steel plates and steel fasteners was examined by Mehra et al. [7]. Mehra et al. [7] experimentally tested a series of spliced beam-beam connections utilising compressed wood (CW) material in the form of dowels and plates. The CW plates and dowels were manufactured using Scots Pine wood compressed in the radial direction with a compression ratio of approximately 54%. ...
... The final density of the compressed wood material ranged from 1100-1500 kg/m 3 . The results demonstrated that the all-wood connections utilising modified wood could achieve approximately 80% of the load capacity achieved with comparable connections utilising steel components [7]. A finite element (FE) numerical model, capable of predicting the load-displacement behaviour of the adhesive free connections is developed and validated against the experimental results presented by Mehra et al. [7]. ...
Conference Paper
Full-text available
An investigation was carried out to examine the potential to use modified wood as a replacement for metallic connections in timber structures. In recent years, there have been several studies examining the potential to utilise modified wood to improve the performance of engineered wood products. This study describes the development of finite element models validated against a series of experimental tests on spliced beam-beam timber connections. The spliced beams are formed using compressed wood (CW) dowels and slotted-in CW plates providing an all-timber solution. A parametric study is utilised to optimise the design of spliced beam-beam timber connections utilising CW plates and dowels. The parameters studied were dowel arrangement, plate length, plate thickness, beam width and depth. The results indicate that connections using CW dowels and plates can be successfully modelled using finite element (FE) software. An optimised design has been developed to improve stiffness and moment rotation capacity of the connection system.
... Applying heat to the wood in the range of 120-160°C results in softening of the lignin which enables the compression of the wood cell walls under a compressive load [21][22][23]. The resulting densified product has been shown to have excellent properties in terms of strength, stiffness and hardness making it suitable for demanding applications [21,24]. Sotayo et al. [21] have shown that increases in strength and stiffness in the region of 100-200% are not uncommon but it should be noted that the results are dependent on species, degree of compression and pressing temperature to name a few of the most influential factors. ...
... Sotayo et al. [21] have shown that increases in strength and stiffness in the region of 100-200% are not uncommon but it should be noted that the results are dependent on species, degree of compression and pressing temperature to name a few of the most influential factors. Mehra et al. [24] demonstrated that densified wood in the form of dowels could even rival steel dowels in a beam-beam spliced connection achieving only 20% less in terms of failure load for comparable designs. The use of densified dowels has recently been examined as a potential method of reinforcement against compressive loads perpendicular to the grain [25] in a similar method currently used with self-tapping screws. ...
... There have been a number of studies that have addressed the used of steel dowels or self-tapping screws as compression reinforcement perpendicular to the grain [17,18,25,33,36,37]. In more recent times, the use of densified wood has been examined in a number of different structural applications, which have shown that densified wood material has increased density, strength, stiffness, hardness and reduced porosity [24]. Typically, it has been shown that as the density of the dowel is increased, there is a proportional improvement in elastic modulus and strength [38,39]. ...
Article
Full-text available
In recent years, the construction industry has seen a greater focus on the use of sustainable construction materials to reduce the environmental impact of buildings. Timber is one such material that has seen a revival in its use due to its environmental credentials coupled with advances in the manufacture of engineered wood products and connection technologies. While timber and engineered wood products have a high strength-to-weight ratio suitable for large scale construction, timber is an orthotropic material and demonstrates poorer strength when loaded perpendicular to the grain. As a result, special consideration must be given to the design of areas of support where stress perpendicular to the grain develops in timber structures. This paper describes a study which examines the use of densified wood dowels as a sustainable reinforcement against perpendicular to the grain stresses using experimental and numerical approaches. Glued laminated timber samples were reinforced with 2, 4 and 6 densified wood dowels. The experimental results show significant improvements in load-bearing capacity can be achieved. A full 3-dimensional solid finite element model has been implemented in ABAQUS/Explicit software. The numerical model utilises cohesive zone modelling (CZM) and Hill plastic yield criterion to predict the failure behaviour of specimens utilising densified wood dowel reinforcement. The examined numerical modelling approach has been shown to give good predictions of the performance of the dowel-timber interaction and load-bearing capacity of the composite system. The numerical model has been also used in a parametric study to examine the influence of dowel diameter and dowel length on the failure behaviour. A maximum dowel length-to-diameter ratio is recommended based on the numerical results
... However, there was no comparison of the structural performance to commonly used timbersteel type connections. Mehra et al. [48] investigated the structural performance of CW connectors within a flitch plate type moment connection and compared this to equivalent slotted-in steel plate connections which are commonly used in timber connections. It was shown that the CW-timber connection system achieved a mean failure load of about 80% of that achieved for an equivalent steel-timber connection system. ...
... where F y is the yield load, determined as the intersection between the secant and tangent line on two sections of the load-deformation curve and d is the diameter of the CW dowel. In addition to interlaminar shear failure, some connection specimens exhibited cross-grain shear failure of the CW dowels as reported by Mehra et al. [48,58]. Therefore, the crossgrain shear strength of CW dowels was also experimentally tested and considered for the design calculations in this study. ...
Article
Full-text available
The widespread use of energy-intensive metallic connectors and synthetic adhesives in modern timber construction has negative implications for the end-of-life disposal or re-use of the structural timber components. Therefore, it is favourable to substitute metallic connectors and synthetic adhesives with bio-based alternatives such as wood-based connectors. Recent studies have shown that densified or compressed wood (CW) with superior mechanical properties could be suitable for the manufacture of wood-based connectors in the form of CW dowels and CW plates. This study experimentally examines the moment-rotation behaviour of semi-rigid type timber-CW beam-beam connections under pure bending. The study also assesses the suitability of current design rules to predict the moment capacity of timber-CW connections. The comparative study has shown that the moment capacity of the timber-CW connection can be conservatively predicted from the characteristic load-carrying capacity of the connections calculated using the EC 5 strength equations.
... In this study, this species is subjected to a process of thermo-mechanical compression which involves the compression of wood under heat and pressure to form a material of superior performance. The thermo-mechanical compression of wood typically results in increased density, decreased porosity and improved material strength, stiffness, hardness and dimensional stability making it highly suited to demanding applications [3][4][5][6][7]. Some studies on various softwood species have achieved strength and stiffness increases of more than double that of the un-compressed wood counterpart [8,9]. ...
... A primary aim of densification of wood to produce compressed wood is to increase the mechanical properties by reducing the pores and voids (lumen) between the cell walls, thus increasing the density and other mechanical properties (e.g., strength, elastic modulus etc.). The typical process of thermo-mechanical compression involves the use of a heated press [3]. The un-compressed specimen is placed between the platens of a heated press and the timber is allowed to reach the desired temperature. ...
Conference Paper
Full-text available
An investigation was carried out to examine the potential to manufacture a compressed wood product from fast-grown Sitka spruce, using a process of thermo-mechanical compression to increase its strength and stiffness. The process involves subjecting timber to a thermal load followed by a compressive load to reduce its cross-section, increasing its density and improving its structural performance. In this study, the influence of the manufacturing parameters, specifically, the pressing time and compression ratio, are examined. These parameters have been evaluated based on the microscopic structure and bending strength from three-point bending tests. The results have demonstrated that there is significant potential to manufacture a compressed wood product with improved structural behaviour from fast grown timber.
... In this study, timber elements reinforced perpendicular to the grain with densified wood (DW) dowels are compared with those reinforced with steel screws. Densified wood dowels are made from softwoods that have been radially compressed under heat and pressure, which enhances their structural properties, and they have been shown to have excellent properties when used in timber connections [8,9]. Test configurations with 2, 4 and 6 screws/dowels are examined and compared to unreinforced timber specimens. ...
... The dowels were manufactured by heating the dowels to 130°C over a 1hour period and then compressing the timber at this temperature for 1-hour. The dowels were then cooled under pressure until the temperature was less than 66°C [8]. This resulted in a final mean density ranging between 1100-1500 kg/m 3 . ...
Conference Paper
Full-text available
An investigation was carried out to examine the potential to utilise modified wood as a reinforcement for timber subjected to compression loading perpendicular to the grain. In recent years there has been a significant number of studies examining the use of steel screws and bonded in rods for this purpose. This is becoming more and more important with the increased use of timber in medium-to high rise structures. In this study, thermally densified or modified timber in the form of dowels are utilised as compression reinforcement perpendicular to the grain and tested to failure. Thermally densified dowel reinforcement arrangements of 2, 4, and 6 dowels are examined experimentally under a compressive load and compared to timber samples similarly reinforced but with steel screws specifically designed to resist stresses perpendicular to the grain. The results have demonstrated the potential to utilised modified wood to create an all-wood solution to reinforce against compressive stresses perpendicular to the grain.
... Densified wood nail [3] and dowel [4][5][6][7] were used to assemble the timber elements in shear joints as shown in Fig. 1a. Densified wood plates and dowels were used to connect timber members in beam-column connections [8][9][10] as shown in Fig. 1b and beam-beam connections [11] as shown in Fig. 1c. And also, densified wood dowels were used in bonded-in rod joints [12,13] as shown in Fig. 1d. ...
... Due to the low density (330 kg m -3 ), Japanese Cedar (Cryptomeria japonica) was adopted to fabricate the densified wood used as connectors in the literature [5,[8][9][10]13]. In addition, Scots Pine (Pinus sylvestris) [11] and Spruce (Picea Abies) [7] were also made into densified wood used as connectors. However, the densified poplar has been rarely reported as connection material. ...
Article
Full-text available
The development of eco-friendly connection material instead of steel is a challenging problem in timber structures. Following densification, the mechanical properties of low-density species can be significantly improved. Densified wood may be a potential connection material in timber structures. This paper reviewed the different processing for densified wood, and obtained favorable mechanical properties and dimensional stability based on small specimen sizes, which are much less than the applicable sizes in practice. A densification processing with alkali pretreatment was adopted for poplar widely cultivated in the world to produce the densified poplar, which has been rarely reported as connection material. Various specimens of densified poplar were tested to obtain their main mechanical properties such as strength and deformability. The set recovery of densified poplar was also measured to observe their dimensional stability. In addition, the hygroscopic swelling strains for the diameter of densified poplar dowel were measured to present their moisture-dependent behavior. The improved mechanical properties and dimensional stability confirmed the fact that densified poplar with alkali pretreatment can be an optimal connection material. Graphical abstract
... Namari et al. [15] provides an exhaustive database on the structural strength and stiffness properties of CW in a number of different loading conditions. A series of studies has examined the use of CW in structural timber applications and indicated that CW could be an ideal choice for manufacturing woodbased connectors for structural applications [16][17][18][19][20][21][22]. Mehra et al. [17] examined beam-beam spliced connections using CW connectors and when compared to comparable steel connectors, demonstrated that the CW solution could achieve 80% of the steel solution. ...
Article
Full-text available
The use of timber in construction in medium–high rise construction has increased in recent years largely due to the significant innovation in engineered wood products and connection technology coupled with a desire to utilise more environmentally sustainable construction materials. While engineered wood products offer a low-carbon solution to the construction industry, the widespread use of adhesive and metallic fasteners often limits the recyclability of the structural components at the end of life of the structure and it may be beneficial to reduce this where possible. To establish the possibility of an all-wood connection solution, this preliminary study examines a series of beam-column connections designs to evaluate the relative performance of the different designs, which are connected with modified or compressed wood (CW) connectors. The connection designs are formed between glued-laminated beam and column members in the first instance and later examined when connecting dowel-laminated timber (DLT) members. The results show that significant moment capacity and rotational stiffness can be achieved for connections solely connected using CW fasteners. Furthermore, the all-wood solution utilising CW fasteners to connect DLT members has also demonstrated significant moment capacity and rotational stiffness capacity without the use of adhesive and metallic components.
... Thermal compression method (TM) has been widely used to improve material properties of low-density wood to be more suitable for structural applications [7][8][9][10][11]. The advantage of this method is that it could be easily employed in practice as it requires only a hot press machine. ...
Article
This experimental study aims to improve the engineering properties of coconut wood by using a thermal compression method (TM). The effects of original wood density and compression ratio on the pressing characteristic as well as physical and mechanical properties of thermally densified coconut wood were evaluated. Coconut wood boards obtained from the plantation located in Nakhon Si Thammarat province, Thailand, were sorted into low-density (359 ± 36 kg/m 3) and medium-density (532 ± 35 kg/m 3) groups. They were compressed by 25%, 40%, 55%, and 70% of their original thicknesses under a clamping pressure of 19.6 MPa (pressure gauge), at a temperature of 140 • C for 15 min. The physical and mechanical properties of the densified specimens were measured and compared with the control group specimens. Low-density specimens could be compressed with a higher degree of densification without shape distortion. Thermal compression improved bending strength, modulus of elasticity, compressive strength parallel to grain, and perpendicular-to-grain shear strength up to 125%, 54%, 112%, and 129%, respectively, for low-density wood and 47%, 13%, 41%, and 58%, respectively, for medium density wood. However, the densification did not improve parallel-to-grain shear strength. When the low-density and medium-density wood were compressed to the same density, the densified specimens manufactured from the medium-density group showed more improved dimensional stability, shear strength, and bending properties than those manufactured from the low-density group, while their parallel-to-grain compressive strength properties were not significantly different. However, at the same density level, the natural wood mechanically outperformed the densified wood except for the perpendicular-to-grain shear strength, parallel-to-grain compressive strength, and bending strength perspectives. Thus, the experimental results indicate that the densified coconut wood can be used for structural applications where parallel-to-grain compressive strength or perpendicular-to-grain shear strength is critical.
... Bu bağlantı bölgesinde çivi, vida veya mekanik ankraj benzeri bağlantı elemanlarının kullanılmasının bağlantının taşıma gücü, genel yük-deplasman davranışı, bağlantı bölgesi boyunca meydana gelen gerilme dağılımı ve kayma gerilmesi-kayma deplasmanı davranışları üzerinde ne ölçüde etkili olduğu incelenmesi gerekli olan, bu konudaki literatüre katkı sağlayacağı düşünülen önemli bir konudur. Ahşap-ahşap bağlantı noktaları ile oluşturulan genel ahşap yapı taşıyıcı sistemlerinin taşıma güçleri ve genel yükdeplasman davranışlarının gerçekçi bir şekilde hesaplanabilmesi için bu sistemlerde yer alan bağlantı noktalarının kapasitelerinin gerçekçi bir şekide hesaplanabilmesi bir gereklilik haline gelmiştir (Schiere et al., 2018;Mehra et al., 2018;Izzi et al., 2018). Bu nedenle kapsamlı deneysel bir çalışma planlanmıştır. ...
Article
Full-text available
The general load-displacement and shear stress-shear displacement behavior of the joining area combined with adhesive and mechanical connectivity in wooden structures and structural elements are highly effective on the capacity of the structural system and collapse mechanisms. The behavior of the wood joining area is an important subject that needs to be examined. Also, it exhibits different shear stress-shear displacement behaviors that vary greatly according to the mechanical properties, structure, and type of the material. The comprehensive experimental study examining the general load-displacement behavior, stress distributions and shear stress-shear displacement behaviors in the connection area which wood structural elements are combined with adhesive or adhesive and mechanical anchors have not been found in the literature. Therefore, an experimental study was planned. In this study, the general load-displacement behavior of the timber connection regions which are connected by adhesive and mechanical anchors together with adhesive, with varying length of 180, 240 and 350 mm are investigated experimentally. Besides, the effect of changing in the number and location of mechanic anchors used in the connection area on the general load-displacement and shear stress-shear displacement behavior was also investigated.
Conference Paper
Full-text available
Recently, moment resistance of multiple-fastener connection is analyzed semi-empirically by using experimental data of single fastener connection and conventional strength analysis. One shortcoming of this method is incapability of predicting the ultimate resistance because multiple-fastener connections mostly fail due to splitting as rarely observed in single fastener connection test. In this study, therefore, the ultimate resistance is estimated by means of Tsai-Hill failure criterion and linear elastic fracture mechanic (LEFM). In the framework of LEFM, a model of beam on elastic deformable foundation is developed and numerically analyzed by finite element method. Analysis shows that the main deficiency of predicting the ultimate moment resistance using test result of single fastener connection is successfully minimized. Ultimate resistance of LEFM and Tsai-Hill failure criterion could be designated as the lower and the upper bounds, respectively. In some specimens, the ultimate moment resistances of predictions well agree with the test results.
Article
Full-text available
This study addresses the application of compressed wood (CW) made of Japanese cedar, as a substitute for high-density hardwood, to shear dowel. A double wood-to-wood shear test was performed to evaluate the mechanical shear properties of CW perpendicular to the grain, and the results were compared with those of several types of dowel material. CW with its annual ring radial to loading direction (0 degrees) had a unique double shear performance characteristic, and showed good properties as a dowel material by virtue of its strength and rich ductility. In contrast, CW with its annual ring tangential to loading direction (90 degrees) and maple exhibited brittle failure. While thickness of the base member was varied, the ductility of the joint became stable for diameter over 36 mm and 24 mm thickness for the main and side members, respectively. When the density of the base member increased, its stiffness, yield load, and maximum load exhibited proportional improvement with different inclinations; however, in the case of a maple dowel, the increases were small. When the density of the base member was increased, the ultimate load had positive linear tendency, whereas plastic modulus decreased. Consequently, almost constant energy absorption was observed in spite of the increased density. The optimum load-carrying capacity and ductility of a compressed wooden dowel joint could be designed by introducing an appropriate base member.
Article
Full-text available
In the present study, a plate and a doweled fastener made of compressed wood (CW) were newly introduced into a moment resisting column-beam joint system for a small portal frame structure. A mechanical model that contains not only an axial spring, but also a rotational spring, considered resistant factors to verify how each element resists rotation. Theoretical performance was compared with experimental data. Consequently, the mechanical model was shown to be suitable and the combination of resisting factors was found to be very effective; i.e., the rotational spring provides more influence on the stiffness and moment compared with the axial spring. Large moment and ductility can be achieved by virtue of the high embedding performance of the CW plate in the rotational spring, accompanied with the high shearing performance of the CW dowel in the axial spring. Key wordsMoment resisting joint-Semirigid portal frame-Axial spring-Rotational spring
Conference Paper
In this study, five full-scale bolted glulam beam-to-beam connections with slotted-in steel plates were conducted under a third-point loading, and a three-dimensional finite element method based model was also established to investigate the failure modes and moment resistance of such connections. A material model based on the Continuum Damage Mechanics (CDM) theory was developed to predict damage evolution of wood. Different damage variables were used to consider the ductile and brittle failure modes of wood, respectively. The test results indicated that splitting and shear plug failures were the main failure modes. The numerical analysis model prediction achieved fair agreements with the test results. The research could provide the guide for the design of bolted beam-to-column connections in heavy timber structures.
Article
The use of wood-based connectors as a possible substitute of metal fasteners, for specific applications, in modestly loaded and moderately dense timber components, in new timber assemblies as well as for restoration works, is discussed. The densification technique has been used to obtain a wood-based material with higher mechanical performance with respect to the natural wood. A dedicated research has been carried out to monitor the compression behaviour of the wooden nails. The progress of pushing force during insertion of the wooden nails into wood samples was analysed and served for insertion process control. 600 compression tests were carried out to evaluate the mechanical behaviour of densified wooden nails, obtained from four different hardwood species and with different densification ratios. Beech, densified at 0° ring angle, 60% densification ratio, was selected for the further experimental campaign on the joints. Ten push-out tests have been performed on timber-to-timber joints. Results in terms of rigidity, resistance and post-elastic behaviour are discussed. The observed variability (slip modulus CoV = 26.7%, maximum load CoV = 23.7%) is mainly dependent on the occurrence of geometric flaws during nail insertion. Ductility exhibited by a group of joints was given by nail embedding into the wood before failure as well as by the bending resistance of the nail. The choice of an optimized technology for wood densification and for nail insertion is considered as a key factor for the optimal employment of the novel connectors.
Article
We examined the bending and shear properties of compressed wood using small and clear specimens of Sitka spruce (Picea sitchensis Carr.). For measuring the bending properties, three-point bending tests were conducted under the span/depth ratio of 14, which is standardized in the American Society for Testing and Materials [ASTM D143-94 (2005a)] and Japanese Industrial Standards [JIS Z2101-94 (1994)]. In the bending test, the load, deflection at the midspan, and strain at the bottom of the midspan were simultaneously measured, and Young’s modulus and bending strength were obtained by elementary beam theory. For obtaining the shear modulus and shear strength, asymmetric four-point bending tests were conducted using the specimens with rectangular and side-grooved cross sections, respectively, and the influence of the compression ratio on the shear properties was examined. The results are summarized as follows: (1) Young’s modulus increased with increasing compression ratio when it was determined by the load–strain relation. Nevertheless, this tendency was rather obscured when Young’s modulus was determined by the load–deflection relation. Hence, it is preferable that Young’s modulus is measured from the load–strain relation. (2) The shear modulus in the longitudinal–tangential plane was maximum at the compression ratio of 50%, whereas that in the longitudinal–radial plane was minimum at the compression ratio of 50%. (3) The influence of the compression on the bending and shear strength ratio was not significant.
An historical study of wood fasteners used in wood work
  • E P Suter
E.P. Suter, An historical study of wood fasteners used in wood work. M.Sc. Thesis, North Texas State College Jonesboro, Texas, 1953.
  • J D Edwards
  • N Verton
J.D. Edwards, N. Verton, A Creole Lexicon Architecture, Landscape, People, Louisiana State University Press, Baton Rouge, 2004.
Strength property of densified Sugi adopted as material of connector
  • K Tanaka
  • Y Demoto
  • J Ouchi
  • M Inoue
K. Tanaka, Y. Demoto, J. Ouchi, M. Inoue, Strength property of densified Sugi adopted as material of connector, in: Proceedings of the World Conference on Timber Engineering (WCTE), Trentino (Italy), 2010.