Mechanical property of laminated bamboo in columbia

López , Graduate Research Assistant, Universidad de los Andes, Bogotá, Colombia Summary: A study is conducted to establish the suitability of Colombian glued laminated bamboo Guadua An

Mechanical properties of colombian glued laminated bamboo

Juan F Correal Director of Integrated Civil & Environmental Engineering Lab & Assistant Professor,

Universidad de Los Andes Bogotá, Colombia (Luis F López , Graduate Research Assistant, Universidad de los Andes, Bogotá, Colombia)

Summary: A study is conducted to establish the suitability of Colombian glued laminated bamboo

(Guadua Angustifolia Kunt ) for structural applications As part of this study, selected mechanical properties are reported in this paper Results confirm that glued laminated Guadua (GLG) has similar mechanical properties to best structural wood in Colombia A comparison of the mechanical properties obtained in this research with the corresponding data reported around the world indicates that GLB can be suitable material for construction and design of structural elements

1 Introduction

About 52,000 hectares of specie of bamboo called Guadua Angustifolia Kunt grows naturally in some regions in Colombia Only 40% of the Guadua bamboo is used in structural applications, mainly as material for falsework in the construction of concrete floors In the country, there has been some intent to use Guadua bamboo as structural material with a relative good success Nevertheless, one

of the problems with the Guadua culm is the variability of the mechanical properties Taking into account the currently standardization of the construction industry, glued laminated Guadua has surged as an excellent alternative for a proper prefabricated manufacturing and assembly

construction process of structural elements Preliminary research (Duran, 2003 and Vanegas, 2003) indicated that the laminated Guadua has an excellent mechanical properties and it is as good as the best structural wood in Colombia

The Universidad de Los Andes in Bogotá is conducting for the first time in Colombia a detailed study of the structural performance of the glued laminated Guadua This research consists of

physical and mechanical characterization, strength verification of structural elements, behavior of typical connections and seismic validations of construction system Selected mechanical properties

of the glued laminated Guadua like: compressive strength perpendicular and parallel to grain, tensile strength perpendicular to grain, flexural strength, shear strength parallel to grain and internal bond strength are presented in this paper A comparison of the mechanical properties obtained in this research with the corresponding data reported around the world is shown

2 Material and production method

2.1 Material

Guadua bamboo culms with and average base diameter of 14 cmto 7 cm and height of 30 m are obtained from Caidedonia-Valle in Colombia The average thickness of the culm wall varies from 0.8 cm to 2.0 cm The age of the bamboo varies from 4 to 6 years The culms are cut into 2 to 3 meters lengths and they are taking into the warehouse of the factory

2.2 Production Method

The manufacture of the laminated Guadua is made in Colguadua Ltda factory The culms sections

of 2m to 3m are cut again into 1m to 1.5m in order to have straight pieces Each piece is split in the radial direction into proper number of slices and the node sections are removed The slices are dried

in oven to an average of 6% to 8% moisture content Once the slices are dried, they are immersed in chemical solution to protect bamboo against insects attack Each slice is machined by cutting off the inner and outer faces and form Guadua lamina with thickness from 7 mm to 10 mm All laminas are impregnated with polyvinyl acetate (PVA) adhesive and staked to form laminated Guadua

sheeting Each laminated Guadua is cold pressed in hydraulic press at a pressure of 2 MPa for 15 minutes

3 Experimental program

Temperature, moisture content and relative humidity were recorded for all specimens Tests were conducted on a MTS Universal Testing Machine at the Material Lab at the Universidad de Los

Andes in Bogotá, Colombia All the specimens follow the specifications of the Colombian Institute

of Standards Techniques (ICONTEC) for woody materials which are based on ASTM D143-52 of

1997 standards Test procedures are summarized as follows:

Compression Parallel to Grain- ICONTEC 784

The specimens were 50 mm by 50 mm in section and 200 mm in length A continuously

compression load with load rate of 0.6mm/min was applied The load-displacement curve is

recorded and the modulus of elasticity (MOE), the proportional limit stress and the ultimate stress are determined

Compression Perpendicular to Grain -ICONTEC 785

The specimens were 50 mm by 50 mm in section and 150 mm in length MTS load frame with a bearing metal plate width 50 mm was used to apply a continuously compression load with load rate

of 0.3mm/min The load was applied up to deformation equal to 5% of the specimen thickness is reached and the stress at that point is calculated The proportional limit stress

Flexural Strength- ICONTEC 663

The specimens were 25 mm by 25 mm in section and 410 mm in length The load was applied at the center of 350 mm span with load rate of 2.5mm/min The failure load is recorded and the module of rupture (MOR) is calculated

Fig 1 Tensile Strength perpendicular to grain

Tensile Strength perpendicular to grain- ICONTEC 784

Figure 1 presents the dimensions of the tensile test specimen The load was applied continuously throughout the test at the rate

of the movable crosshead of 2.5 mm/min Ultimate tensile stress is calculated

Load Direction

(a) (b)

Fig 2 Shear Strength Parallel to Grain

Shear Strength Parallel to Grain- ICONTEC 775

Shear parallel to grain was performed based

on Dimensions of the specimen as well as the test setup are shown in Figure 2 The load was applied continuously throughout the test at the rate of 0.6 mm/min Ultimate shear stress is calculated

Fig 3 Internal Bond Strength

Internal Bond Strength

The block-type glue-line shear test was used to evaluate internal bond strength and it is based on ASTM D1037 Figure 3 presents the dimensions of the test specimen and setup The load was applied through a self aligning seat with a continuous motion of the movable head of the testing machine of 0.6mm/min Shear stress at failure based on maximum load is determined

4 Results and discussion

Test average results with the corresponding number of specimens, temperature, average moisture content and relative humidity are shown in Table 1 An average of 19.7 oC, 11.7 %, and 66.7% of temperature, moisture content and relative humidity were recorded at the moment of the test Also

in Table 1, the 5th percentiles of the results and the corresponding mechanical properties of the structural wood according to Colombian Seismic Regulations (NSR, 1998) are shown for

comparison

33 σ ult = 47.6 5.42 σ ult = 43.59 σ ult = 29.59 22.45 16.33

32 σ pl = 35.71 5.48 σ pl = 32.79 σ pl = ND ND ND

31 MOE= 19,140 8.49 MOE= 16,000.0 MOE= ND ND ND Compresion

perpendicular to grain 29 19.23 10.15 67.57 σ pl = 5.4 14.66 σ pl = 2.63 σ pl = 6.5 4.57 2.45

Tension perpendicular

to grain 17 20.18 12.64 62.59 σ ult = 1.49

29.9 σ ult = 0.76 σ ult = ND ND ND Static bending 21 21.03 12.76 66.4 MOR= 81.9 14.79 MOR= 60.66 MOR= 68.45 48.89 32.6

Shear parallel to grain 30 18.08 10.79 70.18 σ ult = 9.32 12.63 σ ult = 7.68 σ ult = 6.12 4.9 3.27

Glue-line shear test 32 19.25 13.44 70.56 σ ult = 7.92 12.29 σ ult = 6.64 σ ult = ND ND ND

(MPa)

VC (%)

20.5 10.44 63.06 Compresion parallel to

grain

A 5% Percentil (MPa) NSR-98 Wood Grade Glued Laminated Guadua

Result (MPa) N°

Test

T (°C) MC (%)

N°: Number of Specimens, T: Temperature, MC: Moisture content, RH: Relative Humity, σutl : Ultimate Stress, σpl : Proportional Limit Stress, MOE: Elasticity Modulate, MOR: Modulus of rupture, VC: Variation Coefficient

Table 1 Summary of Test Results of Glued Laminated Guadua (GLB)

Load Direction

Load Direction

The compression parallel to grain (CPAG) test showed a combination of crush with buckling failure for most of the specimens The 5% percentile value of the ultimate stress for CPAG is 47% higher than the best Colombian wood (type A) The failure mode of the compression perpendicular to grain (CPEG) test was crushing of the material Relatively low value of the 5th percentile was achieved in CPEG test compare to Colombian wood An additional CPEG test was performed with load applied

to four specimens with vertical adhesive line As a result, the ultimate stress for CPEG with vertical adhesive line increased to 41% compare to CPEG with horizontal adhesive line

Adhesive failure was observed in all the specimens of the tension perpendicular to grain (TPG) test

It seems that the adhesive spread rate was not constant during the construction process of these specimens which could explain the high variation coefficient obtained in the TPG test Delimitation failure was presented in most of the specimens of the static bending (SB) test MOR obtained from the SB test is comparable to the type B Colombian wood The failure mode observed in the shear parallel to grain (SPG) test was shear-off the bamboo specimen The shear strength from SPG test is 25% higher compare to Colombia wood type A The glue-line shear test specimens failed in the interlaminate adhesive as expected

A comparison of compression parallel to grain (CPAG) stress of GLG with different adhesive is shown in Table 2 There was no different between the CPAG stress of GLG with Polychloroprene and the CPAG stress of GLG with PVA In addition, the CPAG stress of GLG with PVA is similar

in magnitude compare with the higher CPAG stress of GLG with urea-formaldehyde resin (UFR)

Urea Formaldehyde Resin

47.2

Urea Formaldehyde Resin

34.0

CORREAL J.,

Guadua angustifolia kunt

Polyvinyl of

Guadua angustifolia kunt

angustifolia kunt

COMPRESION PARALLEL TO GRAIN (MPa)

Table 2 Comparison of Compression Parallel to Grain Stress of GLB

Table 3 shows a comparison of internal bond (IB) strength and MOR of glued laminated Guadua (GLG) and glued laminated Moso bamboo (GLM) The IB strength for PVA adhesive is higher compare to UFR adhesive when it is used in GLG Disregarding the adhesive type, the IB strength

is higher in GLG compare to GLM The different in IB strength in GLB and GLM can be associated with different adhesive spread rates Nonetheless, it seems that the differences in IB strength

between GLG and GLM did not affect the MOR Whereas IB strength between GLG and GLM differ in about 372%, MOR between GLG and GLM differ only 20% It appears that once the optimum amount of adhesive is achieved, the IB strength do not have a significant affect on the MOR (Nugroho and Ando, 2001)

BEAM STATIC BENDING

CORREAL J.,

Guadua

NUGROHO N.,

AUTHOR

ND

BOND (MPa)

NUGROHO N.,

ANDO N.

2.13

ND

LEE A., BAI X.,

angustifolia kunt

RFR

2001

UFR: Urea Formaldehyde Resin, PCP: Polychloroprene, PVA: Polyvinyl of Acetate, RFR: Resorcinol Formaldehyde Resin, E-MDI: Emulsion methyldiisocayanate resin

Table 3 Comparison of Internal Bond Strength and MOR for GLB and Glued Laminated Moso Bamboo

5 Conclusion

Based on the preliminary results of this research, the following conclusions are drawn:

Glued laminated Guadua (Colombian Bamboo) has comparable mechanical properties than

structural Colombian wood In some cause, the mechanical properties of the GLG are better than the best structural wood in Colombia

The compression parallel to grain stress is not affect by the type of adhesive and the internal bond strength in glued laminated Guadua

Modulus of rupture for glued laminated Guadua and glued laminated Moso is not affected by the internal bond strength once the optimum amount of adhesive is achieved In general the MOR of the glued laminated Guadua is comparable with glued laminated Moso

Based on the comparison to structural Colombian wood and glued laminated Moso bamboo, the glued laminated Guadua can be suitable material for construction and design of structural elements

Acknowledgement

The research presented in this paper is sponsored by Universidad de Los Andes Thanks are to A Arias of Colguadua and the staff of the Material Lab at the Universidad de Los Andes in Bogotá, Colombia for their help and support

6 References

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[14] ASTM-D3500-95 Structural Panels in Tension, Sección 4, Vol 4.1wood, July 1997

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[16] ASTM-D4761-96 Mechanical Properties of Lumber and Wood-Base Structural Material, Sección 4, Vol 4.1wood, July 1997