Iosipescu shear test method was applied to engineered bamboo strips that were previously thermo-hydro-mechanically modified. The bamboo species used for this novel testing procedure was Guadua angustifolia Kunth. The research was undertaken at the University of Bath with financial support from Amphibia Group.

1. Guadua-bamboo
Measurement of the in-plane shear moduli of
using the Iosipescu shear test method
17th -22nd Sep. 2015 -Damyang, KOREA
Dr Hector F. Archila
Researcher - Amphibia Group’s CEO

2.  Motivation behind this work - Material
 Why shear?
 The actual work
 Outcomes
 Conclusions
Guadua-bamboo
Iosipescu shear test on Engineered
structural components

3. Motivation

4. Poor man’s timber
Vernacular construction
 Poor design solutions
 Low added value
 Short life span

5. Poor man’s timber
Scaffolding + Artisan work
 Temporary
 Handcraft
Bamboo scaffolders in Hong Kong by by Jeremy Torr, Jan 6, 2012
Source: Red Bulletin magazine
 Labour intensive
 Not standardized
 High maintenance

6. A way forward...

7. Round cane Structural
Engineered products
Traditional construction
• Photo: Stora Enso Building Solutions Kroika
tower) Bridport House, London, UK
Industrial System

8. Vertical pressure + Temp.Cut into strips
(peeled skins)
Heat pressed
Flat densified strips
Round cane
Straight forward processing by THM
From round Guadua to flat sheets

9. Engineered bamboo products
for structural applications
 Engineered
 Predictable
 Durable
 Standardisable
 Buildable
 Viable
 Scalable

10. Testing & Certification
Shear

11. [Image courtesy of mnartists.org]
Source: https://editions.lib.umn.edu/electionacademy/2012/03/22/paper-cuts-are-the-worst-illin/g

12. Failure of a reinforced concrete column during the earthquake in Haiti.
Source: http://degenkolb.com/images/uploads/2010/03/Haiti1_2Sinclair/15ColumnShearFailure.jpg
Shear failure of a bamboo culm along the direction of the fibres
Source: http://www.conbam.info/pagesEN/properties.html
Shear failure
Bamboo & concrete

13. Shear block method for engineered bamboo.
Source: Correal, J. F., Echeverry, J. S., Ramírez, F., & Yamín, L. E. (2014).
Experimental evaluation of physical and mechanical properties of Glued
Laminated Guadua angustifolia Kunth. Construction and Building Materials,
73, 105–112.
Shear testing
Current methods
Shear failure of a bamboo culm along the direction of the fibres
Source: http://www.conbam.info/pagesEN/properties.html

14. The research
Iosipescu Shear
test

15. Iosipescu shear test
Novel method
Shear diagram
Moment diagram
Test diagram
𝑏
Ɩ
𝐹. 𝑏
Ɩ − 𝑏
𝐹. Ɩ
Ɩ − 𝑏
𝐹. Ɩ
Ɩ − 𝑏
𝐹. 𝑏
Ɩ − 𝑏
𝑏/2
+
𝐹. 𝑏
2
−
𝐹. 𝑏
2
0
𝐹
−
𝐹. 𝑏
Ɩ − 𝑏
𝑭𝑭
𝑭 𝑭

16. Sample & Iosipescu shear fixture
θ = 90º
X3 (Radial)
X1(Longitudinal)
X2(Tangential)
Ɩ =71.78 ± 0.25
mm
t = 12.07
± 0.12 mm
h = 17.06
± 0.29 mm
F’
Compressive load on X2
FFixed grip Pivot
Adjustable
jaw
Thumb-screw
Wires from strain gauges to
Data Logger (1,2,3,4)
Strain gauge
(front face 1-2)
X2 (T)
X3 (R)X1 (L)
Face to face strain gauges - Temp= 27º±2ºC, RH = 70±5% - Elastic cycles

17. Test conditions
From round Guadua to flat sheets
SAMPLES
A B C
Control - Dried - Soaked
ρ = 543.3 kg/m3 814.6 kg/m3 890.9 kg/m3
 ASTM D5379 (ASTM 1998);
Pierron & Vautrin (1994)
 Samples conditioned at 27 ±2C
and RH of 70±5% for a period of
20 days (MC=12%)
 Four specimens per sample.

18. Testing & data gathering
INSTRON 5585H floor model testing machine with a 200kN load cell
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2.0
-15'000 -10'000 -5'000 0 5'000 10'000 15'000
Load(N)
Normal strain (µƐ)
-45 front
+45 front
-45 back
+45 back
Ave. +45
Ave. -45
Strain gauges +45 & -45 on
front & back faces
Type: Tee Rosette (90º)
Resistance: 350±0.2%OHMS
Gauge factor: 2.12 NOM
X2 (T)
X1 (L)
α = +45
α’ = -45
Iosipescu
fixture
F’
X1 (L)
X2 (T)
200kN load
cell
F
Specimen
Wires to Data-
logger
Sample C4d
Ave. +45Ave. -45

19. y = 0.0014x + 0.0982
R² = 0.9999
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
18.0
-2'500 0 2'500 5'000 7'500 10'000 12'500 15'000 17'500 20'000
Shearstress(MPa)𝛕
Shear strain (µƐ) ϒ = |µƐ45| + |µƐ-45|
Shear Cord G (Sample C4d)
(ϒ2, τ2)
(ϒ1, τ1)
4,000±200µƐ
Shear modulus ( 𝑮 𝟏𝟐)
Data analysis
𝑮 𝟏𝟐 =
𝛕
ϒ
𝑮 𝟐𝟏
𝒂𝒑𝒑
=
𝝉 𝒂𝒗
ϒ 𝒂𝒗
𝑮 𝟏𝟐
𝒄𝒉𝒐𝒓𝒅
=
∆𝝉
∆ϒ
(𝑮 𝒂 −𝑮 𝒃 )
(𝑮 𝒂 +𝑮 𝒃 )
∙ 𝟏𝟎𝟎
where
∆𝛕 is the difference of shear stress between 𝛕 2
and 𝛕 1 and ∆ϒ is the difference of shear strain
between ϒ 2 and ϒ 1.
𝐺a is the shear modulus of the sample’s side (a)
and 𝐺b is the shear modulus of the sample’s side
(b)

20. Results

21. Apparent Shear modulus ( 𝑮 𝟏𝟐
𝒂𝒑𝒑
)
Low CoV and St. dev.
0.57
0.49
0.54
0.58
0.96
0.89
0.79
0.84
1.41 1.40 1.41 1.42
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
ApparentShearmoduli(GPa)
A1 A2 A3 A4 B1 B2 B3 B4 C1 C2 C3
28%
17%
11%
18%
15%
15%
18%
15%
12%
13%
11%8%
2%
1%
9% 7% 7%
12%
7%
15%
13%
13%
12%
10%
μ=0.54± 0.05
μ=0.87 ± 0.07
μ=1.41 ± 0.06

22. Shear chord modulus ( 𝑮 𝟏𝟐
𝒄𝒉𝒐𝒓𝒅
)
Typical shear stress vs. shear strain graph of specimens A, B & C.
-1
0
1
2
3
4
5
6
7
8
9
-5'000 0 5'000 10'000 15'000 20'000 25'000
Shearstress,𝛕
(MPa)
Shear strain, ϒ (μƐ)
A1 A2 A4 B1 B2 B3 B4 C1 C2 C3 C4 A3
Samples BSamples C
Samples A
Chord modulus
(slope)

23. Shear chord modulus ( 𝑮 𝟏𝟐
𝒄𝒉𝒐𝒓𝒅
)
Box and whisker plots for shear chord results of samples A, B & C.
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
ShearChordModulus
(GPa)
Density (kg/m3)
μ=0.41
μ=0.69
μ=1.32
GA12
GB12
GC12
543.3 814.6 890.9

24. Average, Ga (outer) and Gb (inner) shear chord
moduli values.
A1 A2 A3 A4
A (G average) 0.45 0.42 0.36 0.40
A (Ga outer) 0.44 0.36 0.34 0.34
A (Gb inner) 0.46 0.49 0.39 0.49
A1, 0.45 A2, 0.42
A3, 0.36
A4, 0.40
0.30
0.40
0.50
ShearChord
Modulus
(GPa)
B1 B2 B3 B4
B (G average) 0.71 0.68 0.67 0.69
B (Ga outer) 0.83 0.70 0.71 0.76
B (Gb inner) 0.63 0.66 0.63 0.64
B1; 0.71
B2; 0.68 B3; 0.67 B4; 0.69
0.60
0.65
0.70
0.75
0.80
0.85
ShearChord
Modulus
(GPa)
C1 C2 C3 C4
C (G average) 1.26 1.28 1.33 1.40
C (Ga outer) 1.89 1.68 2.06 2.10
C (Ga inner) 0.94 1.04 0.99 1.05
C1, 1.26 C2, 1.28 C3, 1.33 C4, 1.40
0.70
1.20
1.70
2.20
ShearChord
Modulus
(GPa)

25. Remarks
Increase in shear modulus » THM modification » Higher density
Twist was high within the 0.1% strain range and stabilized as the
load increased; tangential local crushing was observed.
A B C
ρ 543.3 kg/m3 814.6 kg/m3 890.9 kg/m3
𝑮 𝟏𝟐
𝒂𝒑𝒑
0.54 GPa 0.87 GPa 1.41 GPa
𝑮 𝟏𝟐
𝒄𝒉𝒐𝒓𝒅 0.41 GPa 0.69 GPa 1.32 GPa
𝑮 𝟏𝟐
𝒓𝒐𝒖𝒏𝒅
0.58 GPa Takeuchi-Tam (2004)
0.644 GPa Ghavami & Marinho (2005)

26. Conclusions & recommendations
 Adequate method for assessing the shear modulus 𝑮 𝟏𝟐 of
small samples of bamboo.
 Setting guidelines for aiding the development of standards
 Errors due to misalignment, twisting and poor specimen
preparation.
 Key for the development of engineered bamboo products

27. Future of bamboo
Challenge!

28.  Professionalize the “art”
 Exhaustive – rigor
 Learn from mistakes
 Partnership
 International standards
Bamboo based forest sector
Bamboo architecture,
construction and engineering

29. Acknowledgments
Sponsors
&

30. Thanks
&
Questions...?

32. 7.42 6.74
14.86
12.48
0
2
4
6
8
10
12
14
16
CLT-3 CLT-5 G-XLam 3 G-XLam 5
MOE(GPa)
Ec/t,0 Ec/t,90
2x MOE & Density (890kg/m3)
Improved Hardness & resistant to decay
(Twice more load per unit area)
Source image: www.ecobuild.co.uk
480 to 500 kg/m3