MS 544: PART 12: 2006: CODE OF PRACTICE FOR STRUCTURAL USE OF TIMBER – LAMINATED

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

• DEVELOPMENT OF MS 544 PART 12

• CONTENT OF STANDARD

• DESIGN METHOD

• 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

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.

LVL

Loading Direction

Loading

direction

a) Edgewise b) Endwise

Loading direction

Loading direction

c) Flatwise

DEVELOPMENT OF MS 544 PART 12

• Working Group established in 1999.

• First meeting in October 1999.

• Last meeting 1st of August 2002.

• 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 zamin@fk.um.edu.my

• (chairman)

• Dr. Paridah Md. Tahir UPM ftahir@forr.upm.edu.my

• Late Dr. Tan Yu Eng FRIM tanye@frim.gov.my

• Pn. Hanishahani Othman CIDB hani@cidb.gov.my

• En. H’ng Paik San (secretary) UPM pshng@hotmail.com

• Dr. Razali A. Kader Golden Hope razali@goldenhope.com

• Dr. Wong Ee Ding UPM edingw@hotmail.com

• Prof. Madya. Zakiah Ahmad UiTM zakiah@civil.engr.itm.edu.my

• En. Ahmad Fahmi Abdul Ghaffur JPN fahmi@kpkt.gov.my

• En. Haris Alpiah CA haris@casco-adhesives.com

• En. Simon Lee GORISE info@gorise.com

• En. Suhaimi Abu Bakar UTM suhaimi@fka.utm.my

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 • MS 544 : Part 2 : 2001: Permissible stress design for solid timber

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

– Target Moisture content (MC) : 12%

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.

Experimental Design

• 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

Test Design

Loading Directions

Flatwise Edgewise

Load Load

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

Test Setup

• Static bending test setup

• Third point loading (4 point bending)

Test Setup

• 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

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

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 Rafters

Floor beams and joists

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

• 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 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 (Rk)

Rk = [1- (2.7VR/ n)] R 0.05

4

Establish Basic

Working Stress Values

(Rbasic)

Rbasic = Rk /[1.75*(1.3 + 0.7 VR)]

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

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)

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 • 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.

• 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.

DESIGN METHOD

• 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

• The design example can be found in this book

THANK YOU