an innovative and versatile mass timber product - glued laminated timber
DESCRIPTION
This presentation provides a comprehensive overview of glued laminated timber, a building material that is a structural composite of lumber and adhesive. The presentation highlights variations of the building material, with an in depth review of the manufacturing processes. In addition it reviews glued laminated timber’s design properties, how the building material can be used within buildings codes and examples of glued laminated timber being used in commercial buildings from the Tacoma Dome to the Raleigh Durham Airport.TRANSCRIPT
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