MS 544 PART 12

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MS 544: PART 12: 2006: CODE OF PRACTICE FOR MS 544: PART 12: 2006: CODE OF PRACTICE FOR

STRUCTURAL USE OF TIMBER

STRUCTURAL USE OF TIMBER_–_– LA LAMINAMINATEDTED VENEER LUMBER (LVL) FOR STRUCTURAL VENEER LUMBER (LVL) FOR STRUCTURAL

APPLICATION 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

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PRESENTATION OUTLINE

•

INTRODUCTION TO LAMINATED VENEER

LUMBER

•

DEVELOPMENT OF MS 544 PART 12

•

CONTENT OF

CONTENT

OF ST

STANDARD

ANDARD

•

DESIGN METHOD

•

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LAMINATED VENEER LUMBER (LVL)

Laminated veneer Laminated veneer lumber (LVL) is an lumber (LVL) is an engineered wood engineered wood

product that uses

multiple layers of

veneer assembled with

adhesives.

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LVL PROCESS

Veneer oriented in single direction Glue spreading

LVL consists of thin sheets of wood veneer bonded with adhesive and oriented with the grain parallel in the long direction.

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Loading Direction

Loading direction a) Edgewise b) Endwise Loading direction Loading direction c) Flatwise

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DEVELOPMENT OF MS 544 PART 12

•

Working Group established in 1999.

•

First meeting in October 1999.

•

Last meeting 1

st

of August 2002.

•

Total 33 meetings being held to develop this

standard.

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i. Committee of Working Group

• Prof. Madya Dr. Mohd. Zamin Jumaat UM [email protected]

• (chairman)

• Dr. Paridah Md. Tahir UPM [email protected]

• Late Dr. Tan Yu Eng FRIM [email protected]

• Pn. Hanishahani Othman CIDB [email protected]

• En. H’ng Paik San (secretary) UPM [email protected]

• Dr. Razali A. Kader Golden Hope [email protected]

• Dr. Wong Ee Ding UPM [email protected]

• Prof. Madya. Zakiah Ahmad UiTM [email protected]

• En. Ahmad Fahmi Abdul Ghaffur JPN [email protected]

• En. Haris Alpiah CA [email protected]

• En. Simon Lee GORISE [email protected]

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ii. Review of Established Standard

• 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

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iii. Testing of LVL samples

• 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;

– Resin : Phenol formaldehyde (PF) – Board thickness : 50 mm

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3.2 mm 4.0 mm Yellow Meranti 3.2 mm 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 50-mm thick LVL

• 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.

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• Tests that were performed;

– Static Bending

• Flatwise and edgewise

– Bending Shear

• 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

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Loading Directions

Flatwise Edgewise

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Test Samples Tests Loading Directions Size (mm) thickness x width x length Number of specimen Static Bending Flatwise Edgewise 50 x 90 x 900 90 x 50 x 1620 30 30 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

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Test Setup

• Static bending test setup

• Third point loading (4

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Test Setup

• Bending shear test

setup

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Test Setup

• Tensile parallel to the

longitudinal member of LVL test

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Test Setup

• Compression parallel to the

longitudinal member of LVL test

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Basic working stresses and stiffness for

LVL

• Data obtained were analysed into design value according to Basic Working Stress in Bending

In-grade

Species Basic working stress, N/mm2

Bending1 (MOR) Tension parallel to longitudinal axis Shear parallel to longitudinal axis1 Compression parallel to longitudinal 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 Keruing 13.4 9.6 8.3 6.9 1.03 0.63 21.2 14.0 18550 16900 14228 12962

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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

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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.

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B. Application

Load-bearing wall framing Rafters

Floor beams and joists

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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.

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D. Durability

• 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

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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

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The steps involve in the processing the data obtained from a series of mechanical testing in deriving the basic working stress.

Step Definition Formulation

1 Production of raw data Modulus of rupture (MOR), shear, tension and compression values 2

Modification the raw data to 5th_percentile

values. (R_0.05)

or

Using Cumulative Distribution Function 3 Establish Characteristic Test Values (R _k) R _k = [1- (2.7V_R/ n)] R_0.05 4 Establish Basic

Working Stress Values (R _basic)

R _basic = R _k /[1.75*(1.3 + 0.7 V_R)]

Note: = means values = Standard deviation

V_R = Derived coefficient of the variation 1.75 = Load Duration Factor

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F. Design Values

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.

Grade stress for various strength groups of structural LVL (Stresses and elastic moduli expressed in N/mm2₎

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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.

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H. Permissible Stresses

• 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.

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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.

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DESIGN EXAMPLES

• The design example can be