MS 544: PART 12: 2006: CODE OF PRACTICE FOR STRUCTURAL USE OF TIMBER – LAMINA LA MINATED TED VENEER LUMBER (LVL) FOR STRUCTURAL APPLICATION ASSOC PROF. DR. H’NG PAIK SAN MEMBER OF TECHNICAL COMMITTEE ON TIMBER STRUCTURE Institute of Tropical Forestry and Forest Product, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia
PRESENTATION OUTLINE •
INTRODUCTION TO LAMINATED VENEER LUMBER
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DEVELOPMENT OF MS 544 PART 12
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CONTENT OF STANDARD STANDARD
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DESIGN METHOD
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DESIGN EXAMPLE
LAMINATED VENEER LUMBER (LVL)
Laminated veneer lumber (LVL) is an engineered wood product that uses multiple layers of veneer assembled with adhesives.
LVL PROCESS LVL consists of thin sheets of wood veneer bonded with adhesive and oriented with the grain parallel in the long direction.
Glue spreading Veneer oriented in single direction
LVL
Loading Direction Loading direction Loading direction Loading direction
a) Edgewise
b) Endwise
c) Flatwise
DEVELOPMENT OF MS 544 PART 12 •
Working Group established in 1999.
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First meeting in October 1999.
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Last meeting 1st of August 2002.
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Total 33 meetings being held to develop this standard. Standard published in 2006.
i. Committee of Working Group •
Prof. Madya Dr. Mohd. Zamin Jumaat
UM
[email protected]
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(chairman)
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Dr. Paridah Md. Tahir
UPM
[email protected]
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Late Dr. Tan Yu Eng
FRIM
[email protected]
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Pn. Hanishahani Othman
CIDB
[email protected]
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En. H’ng Paik San (secretary)
UPM
[email protected]
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Dr. Razali A. Kader
Golden Hope
[email protected]
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Dr. Wong Ee Ding
UPM
[email protected]
Prof. Madya. Zakiah Ahmad
UiTM
[email protected]
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En. Ahmad Fahmi Abdul Ghaffur
JPN
[email protected]
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En. Haris Alpiah
CA
[email protected]
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En. Simon Lee
GORISE
[email protected]
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En. Suhaimi Abu Bakar
UTM
[email protected]
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ii. Review of Established Standard •
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Design standard based on AS/NZS 4357:1995: Structural laminated veneer lumber AS 4063:1992- Timber—Stress-graded —In-grade strength and stiffness evaluation AS 1720.1-Timber structures - Design methods MS 544 : Part 2 : 2001: Permissible stress design for solid timber MS 544 : Part 5 : 2001: Timber joints BS 6399 : Part 1 : 1984: Loading for buildings: Part 1 : Code of practice for dead and imposed loads BS 6399 : Part 2 : 1997: Loading for buildings: Part 2 : Code of practice for wind loads MS 544 : Part 2 : 2001: Permissible stress design for solid timber
iii. Testing of LVL samples •
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Laminated Veneer Lumber (LVL) were produced from five tropical hardwood species, i.e., Yellow Meranti (Shorea spp), Kedondong (Canarium spp.), Bintangor (Calophyllum spp.) White Meranti (Shorea spp.) and Keruing (Dipterocarpus spp.) The process spec as below; –
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Resin : Phenol formaldehyde (PF) Board thickness : 50 mm Target Moisture content (MC) : 12%
Experimental Design 50-mm thick LVL
Yellow Meranti
3.2 mm
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4.0 mm
Kedondong
3.2 mm
4.0 mm
Bintangor
3.2 mm
4.0 mm
White Meranti
3.2 mm
4.0 mm
Keruing
3.2 mm
4.0 mm
Logs peeled into 3.2 mm and 4.0 mm thick veneer thickness. Veneer layers : 17-ply of 3.2 mm; 13-ply of 4.0 mm to produce 50-mm thick LVL.
Test Design •
Tests that were performed; –
Static Bending •
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Bending Shear •
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Flatwise and edgewise Flatwise and Edgewise
Tensile parallel to the longitudinal of LVL member Compression parallel to the longitudinal of LVL member
All test were performed according to Standard AS/NZS 4357 : Structural Laminated Veneer Lumber
Loading Directions Load
Edgewise
Load
Flatwise
Test Samples Tests
Loading Directions
Static Bending
Flatwise Edgewise
Size (mm) thickness x width x length 50 x 90 x 900 90 x 50 x 1620
Number of specimen
Bending Shear
Flatwise Edgewise
50 x 40 x 300 40 x 50 x 240
30 30
Tensile
50 x 50 x 1500
15
Compression
50 x 50 x 1500
15
30 30
Test Setup
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Static bending test setup Third point loading (4 point bending)
Test Setup
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Bending shear test setup Center point loading
Test Setup •
Tensile parallel to the longitudinal member of LVL test
Test Setup •
Compression parallel to the longitudinal member of LVL test
Lateral restraint
Basic working stresses and stiffness for LVL •
Data obtained were analysed into design value according to Basic Working Stress in Bending In-grade Basic working stress, N/mm2
Species Bending1 (MOR)
Tension Shear parallel to Compression 1 parallel longitudinal axis parallel to to longitudinal longitudinal axis axis
Modulus of elasticity (MOE) 1 Mean
Minimum
Yellow Meranti
10.2
6.9
0.52
18.0
12000
9204
Kedondong
10.6
7.7
0.61
18.7
12500
9588
Bintangor
14.6
9.0
0.94
20.0
14000
10738
White Meranti
13.4
8.3
1.03
21.2
18550
14228
Keruing
9.6
6.9
0.63
14.0
16900
12962
CONTENT OF MS 544 PART 12: • • • • • • • •
1. Scope 2. Referenced documents 3. Definitions 4. Applications 5. Durability 6. Structural properties 7. Connections 8. Permissible stresses
A. Scope This Standard applies to Laminated Veneer Lumber (LVL) products engineered for use in structural applications in which the primary loading is in either the edgewise or endwise direction such as rafters, headers, beams, joists, studs and columns. Secondary gluing shall be permitted for edgewise bending application. Use of scaffold planks or secondary end-jointing is beyond the scope of this Standard.
B. Application
Load-bearing wall framing
Floor beams and joists
Rafters
Lintels
3. Installation
C. Connections Connectors that may work well in solid timber members should be used with caution in LVL as the veneer lathe checks that are formed during peeling can reduce its fracture toughness properties. Since LVL is made up of many layers of veneers, the connectors should be installed perpendicular to gluelines (Figure a) and should is not recommended to be installed parallel to the gluelines (Figure b) such that delamination due to stress concentration between laminates does not occur.
a.
b.
D. Durability •
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Durability refers to the durability of the wood used and the integrity of the glueline. The structural LVL should be manufactured by using a WBP type adhesive, which complies to MS 908. It shall conform to the requirements of Service class III (an external, fully exposed condition including marine environment). LVL is required to maintain its strength and bonding performance up to an equilibrium moisture content (EMC) of 20%. When treatment with preservative is specified, it shall be carried out in accordance with MS 544 Part 10.
E. Structural Properties •
The strength and stiffness of LVL shall be manufactured and evaluated using the methods specified in Malaysian Standard MS 2209: 2009: Structural Laminated Veneer Lumber: Performance Requirements and Minimum Manufacturing Requirements
The steps involve in the processing the data obtained from a series of mechanical testing in deriving the basic working stress. Step
Definition
1
Production of raw data
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Modification the raw data to 5th percentile values. (R 0.05)
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Establish Characteristic Test
Formulation Modulus of rupture (MOR), shear, tension and compression values
or Using Cumulative Distribution Function
R k = [1- (2.7VR / n)] R 0.05
Values (R k )
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Establish Basic Working Stress Values
R basic = R k /[1.75*(1.3 + 0.7 V R )]
(R basic)
Note:
= means values = Standard deviation VR = Derived coefficient of the variation 1.75 = Load Duration Factor 1.3 + 0.7 VR = Safety factor
F. Design Values Grade stress for various strength groups of structural LVL (Stresses and elastic moduli expressed in N/mm2) Strength Group
Bending (MOR)
Tension parallel to longitudinal axis
Shear parallel to longitudinal axis
Compression
Modulus of elasticity (MOE)
Parallel to longitudinal axis
Perpendicular to longitudinal axis
Mean
Minimum
SG1
26.5
15.9
2.28
22.5
3.74
18800
14000
SG2
18.3
11.0
1.95
18.5
3.05
16800
12600
SG3
15.9
9.5
1.61
14.1
2.09
14300
10300
SG4
13.2
7.9
1.23
11.1
1.65
11000
7600
SG5
9.5
5.7
1.07
8.5
1.14
9100
6300
SG6
8.9
5.3
0.86
6.9
1.02
7300
5200
SG7
6.5
3.9
0.76
5.4
0.62
6600
3400
NOTE: The grade stress is adopted from dry standard grade in Table 4, MS 544 Part 2.
G. Connections •
The joint grouping is adopted from MS 544 Part 5 on the basis of testing a single nail size and a single bolt size. Strength Group
SG1
SG2/SG3
SG4
SG5
SG6/SG7
Joint Group
J1
J2
J3
J4
J5
NOTE: The joint group for nails and bolts specified in this Clause should not be used for other fastener types.
Where joints comprise more than one strength group, the design load to be used in the absence of other information is that appropriate to the weakest strength group in the joint.
H. Permissible Stresses •
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Permissible stresses in LVL are governed by the particular conditions of service and loading. The modification factors for LVL were adopted from the MS 544 Part 2: Permissible stress design for solid timber.
DESIGN METHOD •
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LVL can be used wherever sawn timber is used, especially in structural application. The properties of LVL show much less variation than sawn timber. The maximum effect of a single defect in an LVL laminate is very small as the laminates are so thin compared with the thickness of the whole member.
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In Malaysia, currently the timber design is based on the permissible stress theory. In the permissible stress design or allowable stress design, also referred to as elastic design, the stresses developed in a structure due to service or working loads are not allowed to exceed the elastic limit, i.e, the stress levels are limited to the elastic limit. This limit is usually determined by ensuring that stresses remain within the limits through the use of factors of safety.
DESIGN EXAMPLES
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The design example can be found in this book
