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Wood Products Council Webinar O b 27 2010October 27, 2010
Glued Laminated Timber – AnGlued Laminated Timber An Innovative and Versatile Engineered Wood ProductEngineered Wood Product
Tom Williamson, P.E.Consulting EngineerRetired Vice President, APAPast Executive VP, AITC,
Copyright MaterialsCopyright Materials
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di ib i di l d f h idistribution, display and use of the presentation without written permission of the speaker is
Wood Products Council is a Registered Provider with The American Institute of Architects Continuing Education Systems. Credit earned on completion of this program will be reported to CES Records for AIA members. Certificates of Completion for non-AIA members are available on request.
This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or y ppendorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specificin any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.
Learning ObjectivesLearning Objectives
#1 To illustrate how the flexibility of glulam sizes and shapes y g pcan help designers meet their most demanding architectural and structural requirements.
#2 To familiarize designers with how to select and specify#2 To familiarize designers with how to select and specify glulam incorporating new technology and standards changes that have occurred in recent years to expand and enhance the use of glulam as an engineering materialthe use of glulam as an engineering material.
#3 To provide design professionals with an overview of key design considerations that must be considered to ensure b th th t t l f d l t d bilit fboth the structural performance and long-term durability of glulam structures.
#4 To acquaint designers with the unique fire resistive characteristics of glulam as it influences the use of wood in commercial building construction.
What is Glulam?What is Glulam?
Glulam = a structural composite of plumber and adhesives
Anatomy of Glued Laminated TimberAnatomy of Glued Laminated Timber
Lumber LaminationsLumber Laminations
Gl LiGlue Lines
Natural WoodEnd Joints
Natural WoodCharacteristics
Glulam – One of the Original Glued E i d W d C iEngineered Wood Composites
Over 115 years of use worldwide
“Life Cycle”Wood Products“Life Cycle”
Wood ProductsWood ProductsWood Products
Inherent Benefits of GlulamInherent Benefits of Glulam
High degree of engineering High degree of engineering efficiency compared to sawn timber
Engineering EfficiencyEngineering Efficiency
cyy
MSR
Glulam
eque
nc
MSRlumber
ve F
re
Visually graded l bR
elat
iv
Material Property Valueslumber
Dispersal of Strength R d i Ch i iReducing Characteristics
Single LaminationSingle Lamination
Glued Laminated Timber
Inherent Benefits of GlulamInherent Benefits of Glulam
High degree of engineering High degree of engineering efficiency compared to sawn timber Highly efficient use of wood resource from managed forests g
Inherent Benefits of GlulamInherent Benefits of Glulam
High degree of engineering High degree of engineering efficiency compared to sawn timber Highly efficient use of wood resource compared to sawn timberp Large dimensions possible
Spans of 100 feet or greaterSpans of 100 feet or greater Oceans Exhibit – Indianapolis ZooOceans Exhibit Indianapolis Zoo
10-3/4” x 72”10 3/4 x 72115 ft. clear span
Church in Louisville KYChurch in Louisville, KY
12-1/4” x 84”12 1/4 x 84140 ft. clear span
Inherent Benefits of GlulamInherent Benefits of Glulam
High degree of engineering High degree of engineering efficiency compared to sawn timber Highly efficient use of wood resource compared to sawn timberp Large dimensions possible
Vi t ll li it d tilit i Virtually unlimited versatility in shapes and spans
Unmatched Versatility of Sh d SShapes and Spans Inherent Benefits of GlulamInherent Benefits of Glulam
High degree of engineering efficiency compared to sawn timber Highly efficient use of wood resource compared to sawn timbercompared to sawn timber Large dimensions possible Virtually unlimited versatility in shapes Virtually unlimited versatility in shapes and spans
N l h i f d Natural aesthetic appearance of wood
Natural Aesthetics of GlulamNatural Aesthetics of Glulam Inherent Benefits of GlulamInherent Benefits of Glulam
High degree of engineeringHigh degree of engineering efficiency compared to sawn timber Highly efficient use of wood resource Highly efficient use of wood resource compared to sawn timber
L di i ibl Large dimensions possible Virtually unlimited versatility in shapes and spans Natural aesthetic appearance of woodpp Environmentally friendly (green)
Produced from small dimension lumberProduced from small dimension lumber harvested from managed and sustainable forestsTimber resource utilization optimized using a
wide range of lumber gradesUses a wide variety of species Smaller sections required due to higher q g
strengthsManufacturing involves low energy use process Uses low formaldehyde emitting adhesives
Formaldehyde: CARBFormaldehyde CARB
Composite Wood Products
Hardwood plywood
Exempt Products(CARB definition)
Structural plywood (PS1) Hardwood plywood ParticleboardMedium density fiberboard
US Glulam StandardsD l t f D i V lDevelopment of Design Values
D i l d i d i dDesign values are derived in accordance with:
ASTM D3737ASTM D3737
Based on the growthBased on the growth characteristics of lumber (knots, slope of grain and d it )density) Standardized analysis
procedures to generate all major design properties Allows manufacturers to
use computer modelsuse computer models developed by AITC and APA to optimize available resources to achieve highresources to achieve high end performance
ASTM D7341ASTM D7341
Based on full-scaleBased on full scale glulam performance tests in combination with or without modeling
Full Scale Glulam Beam TestsFull Scale Glulam Beam Tests
The U.S. has the largest combined full scale glulam beam database inglulam beam database in the world
Horizontal Shear Values for GlulamHorizontal Shear Values for Glulam
* Volume Effect = 1 0 for bending stresses when* Volume Effect = 1.0 for bending stresses when at least 1.0% of FRP is used
APA Test Program of FRP GlulamAPA Test Program of FRP Glulam
FRP Test Program underway to be used as the FRP Test Program underway to be used as thebasis for APA obtaining an ICC-ESR code report Based on AC 280 and ASTM 7199 Based on AC 280 and ASTM 7199 Based on University of Maine RELAM
computer model with FRP on tension face ofcomputer model with FRP on tension face of the beam Uses lumber properties, FJ strengthUses lumber properties, FJ strength
and FRP characteristics as inputs Completion of this study will make this p y
technology more readily available
Western Washington UniversityWestern Washington University
Small GymSmall Gym12-1/4” x 70” x 78 ft. 10-3/4” x 57” x 78 ft.
Natatorium12 1/4” 81” 91 ft12-1/4” x 81” x 91 ft. 10-3/4” x 64-1/2” x 91 ft.
Western Washington UniversityWestern Washington University
Main GymMain Gym14-1/4” x 90” x 106 ft. 10-3/4” x 75” x 106 ft.
Cost savings for theFRP glulam beamsFRP glulam beamswas $22,000
Basic Glulam Design Considerations
T f b / l d li ti Type of member / load application Determination of allowable design g
20051 General Requirements for Building Design2 Design Values for Structural Members3 Design Provisions and Equations4 Sawn Lumber4 Sawn Lumber5 Structural Glued Laminated Timber6 Round Timber Poles and Piles7 Prefabricated Wood I-Joists8 St t l C it L b8 Structural Composite Lumber9 Wood Structural Panels10 Mechanical Connections11 Dowel-Type Fastenersyp12 Split Ring and Shear Plate Connectors13 Timber Rivets14 Shear Walls and Diaphragms15 Special Loading Conditions15 Special Loading Conditions16 Fire Design of Wood Members
Additional Glulam Design Referencesg
AITC “Timber ConstructionAITC Timber Construction Manual”
McGraw-Hill “APA Engineered gWood Handbook”
McGraw-Hill “Wood Engineering and Construction Handbook”
Glulam Design: 2005 NDSGlulam Design 2005 NDS
Includes both Allowable Stress Design (ASD) and g ( )Load and Resistance Factor Design (LRFD)
LRFD vs. ASDLRFD vs. ASD
LRFD and ASD presentation formats are differentExample equations for bending moment:
Simple span beam with uniform load
ASDApplied stress ≤ Allowable stress
LRFDF d L d F d
ppfb ≤ Fb’
M / Sx ≤ FbCD
Factored Load ≤ Factored Resistance
Mu ≤ Mn’
Mu ≤ Fb KF Sx
End result will be approximatelythe same member size for glulam
Basic Glulam Design Considerations
T f b / l d li ti Type of member / load application Determination of allowable design g
Adjustments for Basic Design ValuesAdjustments for Basic Design Values
F ’ = F C C C (C or C ) CFb’ = Fb CD CM Ct (CL or CV) CC
Fv’ = Fv CD CM Ct
E’ = E CM Ct
C l d d ti f t• CD = load duration factor• CM = wet-use factor (16% or greater)• C = temperature factor• Ct = temperature factor• CL = beam stability factor• CV = volume effect factorCV volume effect factor• CC = curvature factor
Curvature Factor forB di S hBending Strength
C = 1 2000 (t/R)2
t = thickness of lamination (in)R di f t f th l i ti (i )
CC = 1- 2000 (t/R)2
R = radius of curvature of the lamination (in)
R = 27’- 6” for all species with t = 1 5”Rrec = 27 - 6 for all species with t = 1.5Rrec = 9’- 4” for Western species with t = 0.75” Rrec = 7’- 0” for Southern pine with t = 0.75”rec p
Tighter radius can be achieved by using thinner l i ti b t t/R t d 1/100 f S Plaminations but t/R cannot exceed 1/100 for S.P and 1/125 for other softwood species
Volume Factor forB di S hBending Strength
C = ≤ 1.01/x
121/x21 5.125
1/x
Cv ≤ 1.0dL b
L = beam length (ft)d = beam depth (inches)p ( )b = beam width (inches)x = 20 for Southern pinex = 10 for all other species
Impact of Volume Effect FactorImpact of Volume Effect Factor
Size: 8-3/4” x 72” x 100’Size: 8-3/4 x 72 x 100Cv = 0.82 for S.P.Cv = 0.68 for other speciesv pFb’ = 2400 x .82 = 1968 psi for S.P.
Basic Glulam Design Considerations
T f b / l d li ti Type of member / load application Determination of allowable design g
Note the “TOP” Stampf U b l d Lfor Unbalanced Layup
Improper InstallationImproper Installation
Unbalanced Layups“U id D ” B di S“Upside Down” Bending Stresses
Based on full-size beam testsbeam tests conducted at APA, the “upside down”the “upside down” bending stress is 75% of the normal75% of the normal bending capacity
Specifying CamberSpecifying Camber
Glulam can be manufactured with camberGlulam can be manufactured with camberto offset the anticipated dead load deflection Very important for long span members
Specifying CamberSpecifying Camber
Camber can be specified in inches or as a radius of curvatureCamber can be specified in inches or as a radius of curvature
Importance of CamberImportance of Camber
C b b 1”Camber can be < 1”or > 12” dependingon span and loadsp
Field Notching and Drilling of Glued L i d Ti b BLaminated Timber Beams
Notching and DrillingNotching and Drilling
Problem SolutionTension perpendicular
Provide full end grain bearingto grain stresses induced
Provide full end grain bearing
Possible Reinforcement f E d N h i Gl lfor an End Notch in Glulam
Note end notch limitation for glulam
Notching and DrillingNotching and Drilling
T d t i idTapered cut on compression side
Effects of Vertical Holes
Strength reduction = 1.5 x hole diameter/beam width
Example:• 6 3/4” beam width• 6-3/4 beam width• 1” diameter vertical holeReduction = (1.5 x 1.0/6.75)Reduction = 0.22Beam has 78% of original strength
Effects of Vertical HolesEffects of Vertical Holes
The NDS design providesThe NDS design provides nominal lateral and withdrawal values for dowel type connectors (nails screwsconnectors (nails, screws, bolts) and specialty connectors such as shear plates, split rings and timber rivetsand timber rivets
Allowable = nominal x adjustment factors
Adjustment factors account for a wide range of different end use applicationsapplications
wood failure mechanisms need to be considered inneed to be considered in design (this is in addition to yield equations)yield equations)
Local Stresses in Fastener GroupsLocal Stresses in Fastener Groups
Appendix E of NDS: fastenergroup equations/considerations
Durability and Long Term P fPerformance
Proper design MembersMembers ConnectionsP i t ll ti Proper installation Use of wet-use (durable) adhesives Protection from moisture MaintenanceMaintenance
Original U.S. Glulam StructureUSDA F P d L bUSDA Forest Products Laboratory
2008
1934
Durability and Long Term P fPerformance
Glulam Beams Stored Di ib i Y dat Distribution Yard
Glulam Beams Shipped to Job SiteGlulam Beams Shipped to Job Site
Proper handling
Proper storagep g
Interior ApplicationsD bili N T i ll A IDurability Not Typically An Issue
Golf Course BridgeGolf Course Bridge
Pedestrian Bridge - 105 ft spanPedestrian Bridge 105 ft. span Pedestrian Bridge – 120 ft. spanPedestrian Bridge 120 ft. span
Glulam Arch Highway Bridge S d d D k C l dSuspended Deck - Colorado
Glulam Arch Highway Bridge El d D k Mi hiElevated Deck - Michigan
Short Span Glulam RR GirdersShort Span Glulam RR Girders100 ft. Span Glulam
R il d Gi dRailroad Girders
Note centerspan shadow
Glulam Electric Utility StructuresGlulam Electric Utility Structures Tri-Level Highway BridgeKeystone Wye – S.D.
Originalinstallation
2009
1968 Over 40 yearsof exposureto the elements1988 to the elements
Preservative Treatment of GlulamPreservative Treatment of Glulam
U.S. Standards American Wood Preservers Standard (AWPA U1) UC1 Interior, dry Insects UC2 Interior, wet Decay and insectsUC2 Interior, wet Decay and insects UC3 Exterior, above ground Decay and insects UC4 Ground contact Decay and insects UC5 Salt water Salt water organismsUC5 Salt water Salt water organisms
American Association of State Highway and Transportation Officials (AASHTO) Above ground Above ground Ground contact, fresh water Ground contact, salt water
U.S. building codes require treatment of exposed glulam
Preservative Treatment of Glulam s
Preservative forced into wood cells under pressureunder pressure
Untreated glulam in pressure cylinder ready for treatmentready for treatment
Untreated glulamUntreated glulamarches with a closed shoeclosed shoe
No provision such as weep holes to allow
i t t d imoisture to drain
Arch Base to SupportArch Base to Support
N t fl hiNote flashing ontop of glulam
Note open shoe allowing water to drain
After 25 years in service
Arch Base to SupportArch Base to Support
Effects of Moisture ChangesC ion Connections
¼”Glulam¾”Sawn timber Glulam
24”15-1/4”
Green 8%
12% 8%
Green 8%
Glulam Beam End BearingGlulam Beam End Bearing
Cracks developing
Note bearing angleand slight gap at wood
Glulam Beam End BearingGlulam Beam End Bearing
Sol tion alloSolution: allow shrinkage to occur without inducingwithout inducing tension perp stresses
Slotted holes
Importance of DetailingImportance of Detailing
Ends covered
Closed shoe
Lessons Learned to Ensure Durabled L Lif Gl l St tand Long Life Glulam Structures
Keep glulam dry whenever possible Keep glulam dry whenever possible Account for moisture effectsHigh moist re = mold deca insect attackHigh moisture = mold, decay, insect attack
Protect from direct exposure to elements Use preservative treatmentsUse preservative treatmentsUse naturally durable speciesDesign connections for long term performanceg g p
Allow for movement due to moisture changesDesign to avoid moisture entrapmentAvoid direct contact with masonry and concrete
Characteristics of Glulam in FireCharacteristics of Glulam in Fire
Wood is an excellentWood is an excellent heat insulatorDevelops a char layerDevelops a char layer
after fire exposureSelf-extinguishingSelf extinguishing
after fire source removed 10-3/4 x 16-1/2
Retains significant residual strength after being exposed to fire
Glulam vs Unprotected SteelGlulam vs. Unprotected Steel Glulam After ASTM E119 Fire TestGlulam After ASTM E119 Fire Test
Char rate = 1/40” per minute
or1-1/2” per hour
Fire Rating for GlulamFire Rating for Glulam
Two accepted fire rating methodsrating methods recognized in the U.S. IBC Empirical MethodIBC Empirical MethodNDS Mechanics Based
Empirical calculation protocol B d t i t ti i th Based on extensive testing in the U.S. and other countries using theASTM E119 (ISO 834) fi t tASTM E119 (ISO 834) fire test protocol Beams – 3 or 4 sides exposed Columns – 3 or 4 sides exposedp