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 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 Material and production method 2.1 Material Guadua bamboo culms with and average base diameter of 14 cm to 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 to years The culms are cut into to 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 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 MPa for 15 minutes 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 Load Direction (a) (b) Fig Tensile Strength perpendicular to grain Tensile Strength perpendicular to grainICONTEC 784 Figure 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 Shear Strength Parallel to GrainICONTEC 775 Load Direction (a) Shear parallel to grain was performed based on Dimensions of the specimen as well as the test setup are shown in Figure The load was applied continuously throughout the test at the rate of 0.6 mm/min Ultimate shear stress is calculated (b) Fig Shear Strength Parallel to Grain Internal Bond Strength Load Direction (a) The block-type glue-line shear test was used to evaluate internal bond strength and it is based on ASTM D1037 Figure 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 (b) Fig Internal Bond Strength Results and discussion Test average results with the corresponding number of specimens, temperature, average moisture content and relative humidity are shown in Table 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 Glued Laminated Guadua Test Compresion parallel to grain Compresion perpendicular to grain Tension perpendicular to grain N° T (°C) MC (%) RH (%) σult= 47.6 33 32 31 20.5 10.44 63.06 29 19.23 10.15 67.57 20.18 12.64 62.59 17 Result (MPa) σpl= 35.71 MOE= 19,140 σpl= 5.4 σult= 1.49 Static bending 21 21.03 12.76 66.4 MOR= 81.9 Shear parallel to grain 30 18.08 10.79 70.18 σult= 9.32 Glue-line shear test 32 70.56 σult= 7.92 19.25 13.44 NSR-98 Wood Grade 5% Percentil (MPa) VC (%) 5% Percentil (MPa) 5.42 σult= 5.48 8.49 σpl= MOE= 14.66 σpl= 2.63 σpl= 6.5 4.57 2.45 σult= 0.76 σult= ND ND ND 14.79 MOR= 60.66 MOR= 68.45 48.89 32.6 12.63 σult= 7.68 σult= 6.12 4.9 3.27 12.29 σult= 6.64 σult= ND ND 29.9 43.59 32.79 16,000.0 A B σult= 29.59 σpl= ND MOE= ND ND 22.45 ND ND C 16.33 ND ND 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 Summary of Test Results of Glued Laminated Guadua (GLB) 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 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) AUTHOR BARRETO W DURÁN L CORREAL J., LOPEZ L YEAR 2003 2003 2007 BAMBOO Guadua angustifolia kunt Guadua angustifolia kunt Guadua angustifolia kunt ADHESIVE COMPRESION PARALLEL TO GRAIN (MPa) Urea Formaldehyde Resin 47.2 Polychloroprene 46.5 Urea Formaldehyde Resin 34.0 Polychloroprene 46.5 Polyvinyl of Acetate (PVA) 47.6 Table Comparison of Compression Parallel to Grain Stress of GLB Table 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 not have a significant affect on the MOR (Nugroho and Ando, 2001) AUTHOR YEAR BAMBOO ADHESIVE INTERNAL BOND (MPa) BEAM TYPE STATIC BENDING MOR (MPa) BARRETO W 2003 Guadua angustifolia kunt UFR 3.91 ND ND DURÁN L 2003 Guadua angustifolia kunt UFR PCP PVA 3.01 5.67 4.22 ND ND 2007 Guadua angustifolia kunt PVA 7.92 ND 81.9 1998 Moso Bamboo RFR 2.13 2000 Moso Bamboo E-MDI 0.81 2001 Moso Bamboo RFR 0.59 CORREAL J., LOPEZ L LEE A., BAI X., BANGI A P NUGROHO N., ANDO N NUGROHO N., ANDO N H-beam V-beam ND H-beam V-beam 98.6 104.8 76.84 70.31 77.04 UFR: Urea Formaldehyde Resin, PCP: Polychloroprene, PVA: Polyvinyl of Acetate, RFR: Resorcinol Formaldehyde Resin, E-MDI: Emulsion methyldiisocayanate resin Table Comparison of Internal Bond Strength and MOR for GLB and Glued Laminated Moso Bamboo 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 References [1] Barreto C W., Evolución de guadua laminada pegada aplicada a propuesta de reticulado plano, tesis de grado arquitectura Universidad Nacional de Colombia sede Bogota 2003 [2] Duran, L., Estudio de Guadua Laminada y su Aplicación al Sistema Tensegrity, Thesis Work in Architecture, Universidad Nacional de Colombia sede Bogotá, 2003 [3] Lee A., Bai X., Bangai A., Flexural Properties of Bamboo-Reinforced Southern Pine OSB Beams, Journal Forest Products, Jun 1997; 47,6; ABI/IMFORM Global Pg 74 [4] Lee A., Bai X., Bangai A, Selected Properties of Laboratory-Made Laminated-Lumber, Journal Holzforschung, Vol 52, 1998, N°2 [5] Nugroho N., Ando N., Development of Structural Composite Products Made From Bamboo I: Fundamental Properties of Bamboo Zephry Board, Journal Wood Sci, 2000 46: 68-74 [6] Nugroho N., Ando N., Development of Structural Composite Products Made From Bamboo II: Fundamental Properties of Laminated Bamboo Lumber, Journal Wood Sci, 2001 47: 237-242 [7] Vanegas, G, “Guadua Laminada Investigación, Experimentación y Aplicación”, Thesis Work in Architecture, Universidad Nacional de Colombia sede Bogotá, 2003 [8] Junta del Acuerdo de Cartagena, Manual de diseño para maderas del grupo Andino, Junta del acuerdo de Cartagena, Lima, Perú, 1984 [9] Asociación Colombiana de Ingeniería Sísmica, Normas Colombianas de diso sismorresistente (NSR-98), Asociación colombiana de Ingeniería Sísmica, Bogotá, Colombia, 1997 [10] INBAR, GTZ y HFB&YFD, Sustainable Development of the Bamboo and Rattan Sectors in Tropical China, Proceeding No 6, Julio de 2001 [11] ASTM-D143-94, Standard Methods of Testing Small Clear Specimens of Timber, Sección 4, Vol 4.1wood, July 1997 [12] ASTM-D198-94, Standard Methods of Static Text of Lumber Structural Sizes, Sección 4, Vol 4.1wood, July 1997 [13] ASTM-D2718-95, Structural Panels in Planar Shear (Rolling Shear), Sección 4, Vol 4.1wood, July 1997 [14] ASTM-D3500-95 Structural Panels in Tension, Sección 4, Vol 4.1wood, July 1997 [15] ASTM-D3043-95 Plywood in Flexure, Sección 4, Vol 4.1wood, July 1997 [16] ASTM-D4761-96 Mechanical Properties of Lumber and Wood-Base Structural Material, Sección 4, Vol 4.1wood, July 1997 ... 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. .. 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. .. 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 (b) Fig Internal Bond Strength