Glued Laminated Timber An Innovative and Versatile Mass Timber Product

Tom Williamson, P.E. Managing Partner

Timber Engineering LLC

Retired Vice President, APA

Past Executive VP, AITC

What is Glulam?

Glulam = a structural composite of

lumber and adhesives

Anatomy of Glued Laminated Timber

Lumber Laminations

Glue Lines

End Joints

Natural Wood

Characteristics

Glulam: One of the Original Glued Mass Timber Composites

Over 115 years of use worldwide

Original U.S. Glulam Structure USDA Forest Products Laboratory

1934 2009

75 years of continuous use

Large Cross Sections Are Possible

21” x 27” x 110’

Note multiple

pieces positioned

side by side

No reduction in

stress values even

if pieces are not

edge bonded and

load is applied

perpendicular to

the wide face

Unmatched Versatility of Shapes and Spans

Natural Aesthetics of Glulam

An important issue for building

designers is sustainability.

First, wood is green. It is the

only naturally renewable

building material. Second,

Mass Timber is greener. It

maximizes the strength of the

material creating smaller

sections (I-joists in comparison

to sawn joists. Glulams in

comparison to an equivalent

strength sawn beam.) Briefly

review each bullet point above.

Glulam is Environmentally Friendly Sustainable and Green

• Produced from small dimension lumber harvested from

managed and sustainable forests

• Timber resource utilization

optimized using a wide range of

lumber grades

• Uses a wide variety of species

• Smaller sections required due

to higher strengths

• Manufacturing involves low

energy use process

• Uses low formaldehyde

emitting adhesives Mass Timber = Green

Glulam Manufacturing Standard ANSI A190.1

• Specifies product qualification

and quality assurance

requirements

• Third-party inspection by an

approved agency is required on

an on-going basis

• Building codes require that all

glulam must bear a grademark

meeting ANSI A190.1

Material

Preparation

Pre-glue

Layup

End

Joint

Bonding

Face

Bonding

and

Curing

Quality

Verification

Finish

Marking

Shipping

Glulam Manufacturing Process

Lumber Species Used

• Traditional softwoods

• Douglas Fir & Southern Pine

• Other Softwoods

• Spruce/Pine/Fir and Hem-Fir

• Naturally Durable Softwoods

• Alaska Yellow Cedar

• Port Orford Cedar

• Hardwoods

• Mixed species layups

Glulam Adhesive Specifications

Adhesives used for glulam must meet: ASTM D2559 for Exterior-Use

ASTM D7247 for heat durability

Again here is a reminder of the four basic appearance

classifications that we discussed earlier. But to reiterate the line

of distinction between generally stocked beams by your dealer

and those that might be used for exposed aesthetics. For use as

beams and headers where you are comparing glulam against the

other Mass Timber beams and headers you’ll be dealing with the

Framing Appearance category.

Appearance Classifications

• Framing – Intended for concealed applications and is

typically available in 3-1/2” & 5-1/2” widths to match

dimensions of 2x4 and 2x6 framing lumber

• Industrial – Intended for concealed applications or

where appearance is not of primary importance

• Architectural – Used where members are exposed to

view and an attractive finish is desired

• Premium – Available only as a custom order where

appearance is of primary importance

Finishing for Visual Appearance

Strength is not a function of appearance classifications

Quality Trademarks

Basic Glulam Design Considerations

• Type of member/load application

• Determination of allowable design

stresses/layup selection

• Stress modification factors

• Structural analysis

• Special design provisions

• Connection design /detailing

Member Type

Column

Simple span beam

Truss member

Cantilever span beam

Unbalanced Layup

• Unequal capacity

in positive and

negative bending

• Primarily for use

in simple beams

or short

cantilevers

• Requires 5%

tension lams on

the bottom of the

beam

Tension lamination

Balanced Layup

• Equal capacity in

both positive and

negative bending

• Primarily for use

in continuous

beams or long

cantilevers

• Requires 5%

tension lams on

top and bottom of

beam Tension lamination

Tension lamination

Single Grade Layup

• Same lumber

grade and

species used

throughout

• Primarily for use

in axially loaded

members, such

as columns and

truss chords

US Glulam Standards Development of Design Values

Design values are derived in accordance with:

1. Sawn Lumber Grading Agencies

2. Species Combinations

3. Section Properties

4. Design Values

• Lumber and Timber

• Non-North American Sawn

Lumber

• Structural Glued

Laminated Timber

• MSR and MEL

Sources of Design Properties

2005 NDS Supplement

Stress Classes Created for Simplicity

NDS Stress Classes

Sources of Design Properties Industry Standards / ICC Codes

• ANSI 117 Design

Specification

• APA ICC-ESR Code

Report 1940

• Glulam standards

are referenced in the

IBC and IRC codes

LVL Hybrid Glulam with LVL

Outer Laminations

• Full length with no

finger joints required

• LVL has greater tensile

strength compared to

lumber

• 30F-2.1E stress level

achieved

• Direct substitute for many

SCL products

LVL Laminations

LVL “Hybrid” Glulam

• Tested at APA Research Center

• 30F - 2.1E stress grade

• Approved for use in the U.S. by

ICC-ESR code reports

• Limited to depths of 30” or less

Glulam Design: 2005 NDS

1 General Requirements for Building Design

2 Design Values for Structural Members

3 Design Provisions and Equations

4 Sawn Lumber

5 Structural Glued Laminated Timber

6 Round Timber Poles and Piles

7 Prefabricated Wood I-Joists

8 Structural Composite Lumber

9 Wood Structural Panels

10 Mechanical Connections

11 Dowel-Type Fasteners

12 Split Ring and Shear Plate Connectors

13 Timber Rivets

14 Shear Walls and Diaphragms

15 Special Loading Conditions

16 Fire Design of Wood Members

Additional Glulam Design References

• AITC “Timber Construction Manual”

• McGraw-Hill “APA Engineered Wood

Handbook”

• McGraw-Hill “Wood Engineering and

Construction Handbook”

Glulam Design: 2005 NDS

Includes both:

• Allowable Stress Design

(ASD)

and

• Load and Resistance

Factor Design (LRFD)

High Strength Outer Tension Lams

Lower Grade Inner Lams

Medium Grade Inner Compression Lam

High Strength Outer Compression Lams

Unbalanced Layup

Medium Grade Inner Compression Lam

Glulam Layups

Note the “TOP” Stamp for Unbalanced Layup

Specifying Camber

• Glulam can be manufactured with camber to offset

the anticipated dead load deflection

• Very important for longer span members

Specifying Camber

Can be specified in inches or as a radius of curvature

Comparison of Various Radius of Curvature Camber Values

Length 14’ 16’ 18’ 20’ 22’ 24’ 26’

2000’ radius 1/8” 1/4” 1/4” 1/4” 3/8” 3/8” 1/2”

3500’ radius 1/8” 1/8” 1/8” 1/8” 1/4” 1/4” 1/4”

5000’ radius 0 1/8” 1/8” 1/8” 1/8” 1/8” 1/4”

The most common stock beam camber is a 3500’ radius

although some manufacturers supply stock beams with

zero camber.

Glulam Connections Can Be Complex

The NDS Provides Solutions

NDS Connection Design Provisions

The NDS design provides nominal lateral and withdrawal values for dowel type connectors (nails, screws, bolts) and specialty connectors such as shear plates, split rings and timber rivets

Allowable = nominal x adjustment factors

Adjustment factors account for a

wide range of different end use

applications

All applicable to glulam

Durability and Long Term Performance

Strategies for durable glulam construction

• Keep glulam dry

• Focus on design and construction details

• Focus on moisture management

• Use appropriate preservative treatments when

exposed to the elements or

• Specify naturally durable and decay resistive

wood species

• Numerous examples of glulam structures 50-100

years old worldwide

Interior Applications Durability Not Typically An Issue

Pedestrian Bridge - 105 ft. span

Pedestrian Bridge – 120 ft. span

Glulam Electric Utility Structures

Tri-Level Highway Bridge Keystone Wye – S.D.

Original

installation

1968

1988

2009

Over 40 years

of exposure

to the elements

Preservative Treatment of Glulam

U.S. Standards

American Wood Preservers Standard (AWPA U1)

UC1 Interior, dry Insects

UC2 Interior, wet Decay and insects

UC3 Exterior, above ground Decay and insects

UC4 Ground contact Decay and insects

UC5 Salt water Salt water organisms

American Association of State Highway and

Transportation Officials (AASHTO)

Above ground

Ground contact, fresh water

Ground contact, salt water

U.S. building codes require treatment of exposed glulam

Selecting Preservative Treatments For Glulam

Applicable treatments are a function of species and whether

treatment is before or after gluing

See EWS S580C for details

Naturally Durable Species

• Port Orford Cedar 22F-1.8E

• Alaska Yellow Cedar 20F-1.5E

• Western Red Cedar 16F-1.3E

• California Redwood 16F-1.1E

Alaska Yellow Cedar (AYC) Santa Monica, CA Reservoir Cover

Connection Serviceability Issues

• Temperature – not of major importance

• Humidity and moisture – major concerns

exposed end grain

• contact with concrete or masonry

• moisture entrapment

• ambient conditions / dimensional changes

Effects of Moisture

Seasoning

checking

Is it of structural

concern?

Examples of Checking

Side checks

Bottom glue line check

End

checks

Checking vs. Delamination

• Checking is a natural phenomena associated with natural

drying of the glulam

• Delamination is a deterioration of the glue bond when

exposed to moisture

• The introduction of wet-use (durable) adhesives in the

mid 1940’s virtually eliminated delamination in the U.S.

• This is assured by requiring adhesives to meet D2559

and by conducting daily quality control checks using a

cyclic delamination test

Testing by APA conducted to

evaluate impact of checking

• Guidelines established for what

size checks are OK without an

engineering analysis

• Checking rarely affects

structural performance

• Published in an Owners Guide

to Checking

• One of the industry’s most

widely distributed publications

Proper Use of Flashing and End Caps for Long Term Serviceability

Issue: prevent direct water ingress into glulam

• Re-direct the water flow around the connection

• Use preservative treated glulam or durable species

End caps and

flashing used

Proper Glulam Beam to Concrete or Masonry Connection

• Prevent contact with

masonry

• Use steel bearing plate

under beam

• Maintain minimum of

½” air gap at end Note gap

at end

Note steel

bearing

plate

Proper Glulam Arch Base Connection

Note flashing on

top of glulam

Note open shoe

allowing water to drain

After 25 years in service

Lessons Learned to Ensure Durable and Long Life Glulam Structures

• Keep glulam dry whenever possible

• Account for moisture effects

• High moisture = mold, decay, insect attack

• Protect from direct exposure to elements

• Use preservative treatments

• Use naturally durable species

• Design connections for long term performance

• Allow for movement due to moisture changes

• Design to avoid moisture entrapment

• Avoid direct contact with masonry and concrete

Exposed Glulam vs. Unprotected Steel in ASTM E119 Fire Test

Glulam After ASTM E119 Fire Test

Char rate =

1/40” per minute

or

1-1/2” per hour

Characteristics of Glulam in Fire

• Wood is an excellent heat

insulator

• Develops a char layer after

fire exposure

• Self-extinguishing after fire

source removed

• Retains significant residual

strength after being exposed

to fire

10-3/4 x 16-1/2

Glulam beam after 90

minutes of fire exposure

retains 60% of its capacity

Fire Rating for Glulam

Two accepted fire

rating methods

recognized in the U.S.

• IBC Empirical Method

• NDS Mechanics Based

Model

FRT

Flame spread coatings

1- 302-24 Outer Tension Lams

Typical Glulam Beam Layup

24F-V4 Doug Fir (12 Lamination Example)

1 - L2 Grade Inner Comp. Lam

6 - L3 Grade Core Lams

2 - L2 Dense Grade Outer Comp. Lams

For 1-hour fire rated beam: substitute

additional tension lam for core lam

1- L1 Grade Outer Tension Lams 1 - L2 Grade Inner Ten. Lam

Fire Protection

Tension Lam Provisions

Stock beams

often used in

residential

and light

commercial

construction

Stock Beam Manufacturing

Manufactured in long lengths, varying cross-sections,

usually unbalanced, minimal camber

Glulam Beams Stored at Distribution Yard

Glulam Beams Shipped to Job Site

Proper handling

Proper storage

Roof Beams

Stock Beams - Typical Uses

Stock Beams - Typical Uses

Garage Door Headers

Stock Beams - Typical Uses

Simple Span Floor Beams

Continuous Span Floor Beams

Stock Beams – Typical Uses

IJC Beams and Headers

Stock Beams - Typical Uses

• 9-1/2", 11-7/8", 14" & 16" depths

• 3-1/2", 5-1/2" & 7" widths

• Zero or 3500 ft radius camber

• Typical lay-up combinations

• 24F - 1.8E DF & SP

• 30F - 2.1E Hybrid

• 30F - 2.1E SP

I-Joist Compatible (IJC)

Stock Glulam Beams

Advantage of 3-1/2”

and 5-1/2” Widths

2x4 and 2x6 Framing Width Compatible

No 3/8” OSB or other

filler pieces needed

Frames Flush

Axial Loading Combinations

Typical Layup Combinations for Glulam Loaded

Primarily In An Axial Condition Such as a Column

Species Combination No. Grade

Douglas Fir No. 2 L2

No. 5 L1

Southern Pine No. 47 N2M

No. 50 N1D

Alaska Yellow Cedar No. 70 L2

No. 71 L1

Tall wall framing with glulam columns

Typical Column Uses

Typical Column Uses

Tall wall framing with glulam columns

Examples of Glulam Custom Beams and Arches

Bullitt Center Seattle, WA

LeMay America’s Car Museum Tacoma, WA

Airport Terminal Victoria, B.C.

Raleigh Durham Airport

Light Rail Transit Center Vancouver, B.C.

Chicago Bears Football Practice Facility

Disney Twin Rink Ice Arena Anaheim, CA.

Chemical Storage Facility Portland, OR

Cathedral of Light Oakland, CA

2010 Olympic Skating Oval Richmond, B.C.

Toronto Ontario Art Gallery

Tacoma Dome - Tacoma, WA 510 foot clear span

Copyright Materials

This slide presentation is protected by US and

International Copyright laws. Reproduction,

distribution, display and use of the slides in this

presentation without written permission of the

presenter is prohibited.

© T. Williamson – Timber Engineering LLC

2013

Additional Glulam Information

www.apawood.org

Questions Regarding

this Slide Show?

Tom Williamson, P.E.

T. Wiliamson – Timber Engineering LLC

tomwilliamson@live.com