EXPERIMENT INVESTIGATION OF FLEXURE RIGIDITY OF .Experiment Investigation of Flexure Rigidity of

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http://www.iaeme.com/IJCIET/index.asp 771 editor@iaeme.com

International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 8, August 2018, pp. 771780, Article ID: IJCIET_09_08_078

Available online at http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=9&IType=8

ISSN Print: 0976-6308 and ISSN Online: 0976-6316

IAEME Publication Scopus Indexed

EXPERIMENT INVESTIGATION OF FLEXURE

RIGIDITY OF GLUE LAMINATED TIMBER

BEAMS CONSISTING OF COCONUT WOOD

(COCOS NUCIFERA) AND SENGON WOOD

(ALBIZIA FALCATARA) BASED ON FOUR-

POINT BENDING TEST

Kusnindar*

Civil Engineering Department, Brawijaya University,

MT. Haryono street 167 Malang 65145 East Java, Indonesia

Civil Engineering Department, Tadulako University,

Soekarno-Hatta street km.9 Palu, Central of Sulawesi, Indonesia

Sri Murni Dewi

Civil Engineering Department, Brawijaya University,

MT. Haryono street 167 Malang 65145 East Java, Indonesia

Agoes Soehardjono

Civil Engineering Department, Brawijaya University,

MT. Haryono street 167 Malang 65145 East Java, Indonesia

Wisnumurti

Civil Engineering Department, Brawijaya University,

MT. Haryono street 167 Malang 65145 East Java, Indonesia

*Corresponding Author E-mail: kus_untad@yahoo.co.id

ABSTRACT

This paper was intended to describe the performance of mix-glue laminated timber

beams (mix-glulam) compose of coconut wood (Cocos nucifera) and sengon wood

(Albizia falcatara) in the outer zone and core zone, respectively. Mix-glulam system is

an alternative to utilizing a low-grade timber as structural member of building.

Through the analysis of four-point-bending-test results of each of five mix-glulam

beams (BLG) and five sengon-solid beams (SDL) with span (L) = 2750 mm, height (d)

= 155 mm and width (b) = 55 mm was obtained that the mix-glulam system produces

a good performance. The analysis result showed that the flexural rigidity (EI) of BLG

is 1.66 times higher than SDL. Likewise, the maximum bending stress (max) of BLG is

Kusnindar, Sri Murni Dewi, Agoes Soehardjono and Wisnumurti

http://www.iaeme.com/IJCIET/index.asp 772 editor@iaeme.com

1.6 times higher than the max of SDL with tension failure in bending. Generally, the failure of the beam that occurs is a brittle and sudden tension failure.

Key words: sengon wood (Albizia falcatara), coconut wood (Cocos nucifera), mix-

glulam, flexure rigidity, timber beam.

Cite this Article: Kusnindar, Sri Murni Dewi, Agoes Soehardjono and Wisnumurti,

Experiment Investigation of Flexure Rigidity of Glue Laminated Timber Beams

Consisting of Coconut Wood (Cocos Nucifera) and Sengon Wood (Albizia Falcatara)

Based on Four-Point Bending Test. International Journal of Civil Engineering and

Technology, 9(8), 2018, pp. 771-780.

http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=9&IType=8

1. INTRODUCTION

The potential availability of sengon wood (Albizia falcatara) and coconut wood (Cocos

nucifera) in Indonesia is very adequate. In 2013, there are approximately 64 million sengon

trees that can be harvested. This amount is equivalent to 13.9 million m3 of sawn timber [1].

In addition, the potential availability of coconut wood in Indonesia is also quite adequate.

This is a necessity of the extent of the Indonesian coconut plantation which is equivalent to

approximately 26% of the total coconut plantations in the world [2].

Unfortunately, sengon-wood and coconut-wood have not been widely used as structural

elements of building, because in both there are deficiencies in terms of mechanical and

physical properties. Sengon wood has a low-grade modulus of elasticity that is only about

3,881 MPa. While coconut wood has a high variation in the density. The low grade of the

modulus of elasticity causes the carrying capacity of the wood to be low, and the density

variation causes the limitations of sawn timber dimension to be obtained. Approximately only

one-third of the coconut trunk (35 cm diameter) can be utilized to produce good quality sawn

timber with an average elasticity modulus value of 11.414 MPa [2, 3].

In order to utilize sengon and coconut wood for structural elements of building, the mix-

glue laminated timber method can be considered. Mix-glue laminated timber beams is one

type of laminated timber structure product. Mix-glue laminated timber beams consists of two

or more species of timber with different mechanical properties. Timbers that have higher

mechanical properties are placed as outer lamination and vice versa as core elements of the

beam.

Glue lamiated timber (glulam) is still very competitive in modern construction material. In

terms of structural efficiency, the laminated wood can produce construction elements with

sufficient strength to density ratios. For example, the mix-glulam beam composed of

Eucalyptus grandis and Poplar laminations has a structural-efficiency value of 120 x 10-3

MPa.m3/ kg [4]. In this case the structural efficiency of timber structures is better than

concrete [5]. The use of a laminated wood system will produce a large construction elements,

regardless of the diameter of the tree. The cross-section depth of glulam beam is in principle

unlimited, but for the accomplished maximum depths are of the order of 2 m. The weakening

of structures caused by natural wood defects can also be reduced by a laminated wood system

[5].

Based on the above description, this research is aimed to determine the flexure rigidity

and strength of mix-glue laminated timber beam was compose of sengon and coconut wood.

In this case, sengon wood lamination is placed in the core zone of the beam and coconut wood

lamination in the outer zone.

Experiment Investigation of Flexure Rigidity of Glue Laminated Timber Beams Consisting of Coconut

Wood (Cocos Nucifera) and Sengon Wood (Albizia Falcatara) Based on Four-Point Bending Test

http://www.iaeme.com/IJCIET/index.asp 773 editor@iaeme.com

2. LITERATURE REVIEW

Mix-glue laminated timber beams of hardwood timber were composed of 50% of lower grade

lamination in the core zone and 50% of high-grade lamination in the outer zone can produce a

bending strength and stiffness is 16.5 MPa and 12.4 GPa, respectively. This suggests that the

mix-glue laminated timber beam design with this proportion is technically feasible to

implement [6].

Poplar and spruce combinations as mixed-glulam beams result in a more flexible or

pseudo-ductile behavior than individual poplar beams. Based on the load and deformation

relationships, the mix-glulam beams has a plastic behavior till failure [7]. Similarly, the

combination of poplar-larch and poplar-spruce. Both combinations have higher ductility

compared to solid poplar beams, which are 48% and 64% respectively. So, the performance of

mix-glulam-beams is determined by the mechanical properties of the wood species used,

especially the outer zone lamina [8]. Since the ductility of the structure is very advantageous,

it is appropriate that the structural system is designed to behave in a ductile manner. As stated

by [9] that ductility of timber beams can be improved by application of external fiber

reinforcement. This retrofitting method is easy to implement and at the same time reduces the

risk of failure due to defects.

Furthermore, the mix-glue laminated timber beam which is a combination of poplar and

eucalyptus was produced a higher strength and modulus of elasticity than individual poplar

beams. Modulus of elasticity of the mixed-glulam beams is 51% higher than the individual

poplar beam. Likewise, the flexural strength of the mixed-glulam beams was increased by

35% compared to the solid-poplar beams. In this case, poplar wood is placed in the core

lamination and eucalyptus as the outermost lamination, [4].

3. MATERIAL AND METHOD

3.1. Timber and Adhesive

The initial dimensions, mechanical properties and number of lumber prepared for the beam

manufacture are presented in Table 1. Both lumber materials were obtained from sawmills

industry in Malang, East Java, Indonesia. Before use, both are dried for about three months to

achieve air-dry conditions, ie at 12% of moisture content. The physical and mechanical

properties of them are obtained from the clear-specimens test according to [10].

Table 1 Mechanical properties of sengon and coconut wood

Properties in 12% of moisture content Sengon Wood Coconut Wood

Modulus of Elasticity (E12) 3881 MPa 10830 MPa

Modulus of Rupture (MOR12) = 20 MPa 20 MPa 39 MPa

Density (12) 0.29-0.32 gr/cm3 0.6 gr/cm

3

Initial dimension :

width 70 mm;

dept 180 mm; length

3250 mm

width 60 mm;

depth 120 mm; length

3250 mm

Number of the lumber trunks : 15 10

Especially for the manufacture of laminated-timber beams required additional material ie

adhesive. The adhesive used is specifically for wood, ie urea formaldehyde (UF) resin in the

form of ready-made powder. This adhesiv