Guadua-bambooMeasurement of the in-plane shear moduli of

using the Iosipescu shear test method

17th -22nd Sep. 2015 -Damyang, KOREA

Dr Hector F. ArchilaResearcher - Amphibia Group’s CEO

Motivation behind this work - Material Why shear? The actual work Outcomes Conclusions

Guadua-bambooIosipescu shear test on Engineered

structural components

Motivation

Poor man’s timberVernacular construction

Poor design solutions Low added value Short life span

Poor man’s timberScaffolding + Artisan work

Temporary Handcraft

Bamboo scaffolders in Hong Kong by by Jeremy Torr, Jan 6, 2012Source: Red Bulletin magazine

Labour intensive Not standardized High maintenance

A way forward...

Round cane StructuralEngineered products

Traditional construction

• Photo: Stora Enso Building Solutions Kroikatower) Bridport House, London, UK

Industrial System

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

THMT:

CROSS LAMINATION:

Engineered bamboo products

for structural applications

Engineered Predictable Durable Standardisable Buildable Viable Scalable

Testing & Certification

Shear

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

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 fibresSource: http://www.conbam.info/pagesEN/properties.html

Shear failureBamboo & concrete

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 testingCurrent methods

Shear failure of a bamboo culm along the direction of the fibresSource: http://www.conbam.info/pagesEN/properties.html

The research

Iosipescu Sheartest

Iosipescu shear testNovel 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

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

Test conditionsFrom round Guadua to flat sheets

SAMPLES

A B CControl - 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 ±2C and RH of 70±5% for a period of 20 days (MC=12%)

Four specimens per sample.

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

Lo

ad

(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

y = 0.0014x + 0.0982R² = 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

Sh

ear

str

ess (

MP

a) 𝛕

Shear strain (µƐ) ϒ = |µƐ45| + |µƐ-45|

Shear Cord G (Sample C4d)

(ϒ2, τ2)

(ϒ1, τ1)

4,000±200µƐ

Shear modulus (𝑮𝟏𝟐) Data analysis

𝑮𝟏𝟐 =𝛕

ϒ

𝑮𝟐𝟏𝒂𝒑𝒑

=𝝉𝒂𝒗

ϒ𝒂𝒗

𝑮𝟏𝟐𝒄𝒉𝒐𝒓𝒅 =

∆𝝉

∆ϒ

(𝑮𝒂 −𝑮𝒃 )

(𝑮𝒂 +𝑮𝒃 )∙ 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)

Results

Apparent Shear modulus (𝑮𝟏𝟐𝒂𝒑𝒑)

Low CoV and St. dev.

0.570.49

0.540.58

0.960.89

0.790.84

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

Ap

pa

ren

t S

he

ar

mo

du

li (

GP

a)

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

Shear chord modulus (𝑮𝟏𝟐𝒄𝒉𝒐𝒓𝒅)

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

Sh

ear

str

ess,𝛕

(MP

a)

Shear strain, ϒ (μƐ)

A1 A2 A4 B1 B2 B3 B4 C1 C2 C3 C4 A3

Samples BSamples C

Samples A

Chord modulus

(slope)

Shear chord modulus (𝑮𝟏𝟐𝒄𝒉𝒐𝒓𝒅)

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

Sh

ea

r C

ho

rd M

od

ulu

s(G

Pa

)

Density (kg/m3)

μ=0.41

μ=0.69

μ=1.32

GA12

GB12

GC12

543.3 814.6 890.9

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

Sh

ea

r C

ho

rd

Mo

du

lus

(GP

a)

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; 0.71B2; 0.68 B3; 0.67 B4; 0.69

0.60

0.65

0.70

0.75

0.80

0.85

Sh

ea

r C

ho

rd

Mo

du

lus

(GP

a)

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

Sh

ea

r C

ho

rd

Mo

du

lus

(GP

a)

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

𝑮𝟏𝟐𝒂𝒑𝒑 0.54 GPa 0.87 GPa 1.41 GPa

𝑮𝟏𝟐𝒄𝒉𝒐𝒓𝒅 0.41 GPa 0.69 GPa 1.32 GPa

𝑮𝟏𝟐𝒓𝒐𝒖𝒏𝒅

0.58 GPa Takeuchi-Tam (2004)

0.644 GPa Ghavami & Marinho (2005)

Conclusions & recommendations

Adequate method for assessing the shear modulus 𝑮𝟏𝟐 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

Future of bamboo

Challenge!

Professionalize the “art” Exhaustive – rigor Learn from mistakes Partnership International standards

Bamboo based forest sector

Bamboo architecture, construction and engineering

Acknowledgments

Sponsors

&

Thanks &

Questions...?

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

MO

E (G

Pa)

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