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Copyright © 2014 American Wood Council. All rights reserved. 1
Connection Solutions for Wood-frame StructuresMichelle Kam-Biron, PE, SE, SECBDirector of EducationAmerican Wood Council
This presentation is protected by US and International Copyright laws Reproduction
Copyright Materials
International Copyright laws. Reproduction, distribution, display and use of the presentation
without written permission of the speaker is prohibited.
© American Wood Council 2014
2
Copyright © 2014 American Wood Council. All rights reserved. 2
Learning Objectives
• On completion of this course, participants will:
• Be familiar with current wood connection design philosophy,Be familiar with current wood connection design philosophy,
behavior, and serviceability issues.
• Be able to identify basic wood material properties and learn how to
avoid splits, notching, and net section issues in connection solutions
• Be able to recommend fastening guidelines for wood to steel, wood
to concrete, and wood to wood connections.
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to concrete, and wood to wood connections.
• Be able to describe effects of moisture on wood connections and
implement proper detailing to mitigate issues that may occur.
Outline
• Wood connection design philosophy
Connection behavior• Connection behavior
• Serviceability challenges
• Connection hardware and fastening systems
• Connection techniques
• Design software
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• Where to get more information
Copyright © 2014 American Wood Council. All rights reserved. 3
Outline
• Wood connection design philosophy
Connection behavior• Connection behavior
• Serviceability issues
• Connection hardware and fastening systems
• Connection techniques
• Design software
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• Where to get more information
• Model wood cells as a bundle of straws• Bundle is very strong parallel to axis of the straws
Basic Concepts
Parallel Perpendicular
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Stronger Less strong
Copyright © 2014 American Wood Council. All rights reserved. 4
Connecting Wood - Philosophy
• Wood likes compression parallel to grain• makes connecting wood very easy
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• Wood likes compression parallel to grain• makes connecting wood very easy
Connecting Wood - Philosophy
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Copyright © 2014 American Wood Council. All rights reserved. 5
Connecting Wood - Philosophy
• Wood likes to take on load spread over its surface
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Concentrated at a single fastener –wood is more prone to split and crush
Copyright © 2014 American Wood Council. All rights reserved. 6
Connecting Wood - Philosophy
• Wood and tension perpendicular to grain
• Not recommended
Initiators:• notches• large diameter fasteners
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• large diameter fasteners• hanging loads
Notching
Problem Solution
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Copyright © 2014 American Wood Council. All rights reserved. 7
Beam to Concrete
• Notched Beam Bearing
• may cause splitting
Split
may cause splitting
• not recommended
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Beam to Concrete
• Notched Bearing Wall
• alternate to beam notch
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Hanger to Beam
• Load suspended from lower half of beam
• Tension perpendicular to grain
• May cause splits SplitSplit
C
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T
NA
NA
Hanger to Beam
Lower half of beam
• may cause splitsmay cause splits
• not recommended
Exception: light load
• <100 lbs
• >24” o.c.Split
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Split
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Hanger to Beam
• Load supported in upper half of beam
Full wrap sling option
• Extended plates puts wood in compression when loaded
C
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compression T
NA
NA
Connecting Wood- Philosophy
• Splitting happens because wood is relatively weak perpendicular to grain
• Nails too close (act like a wedge)
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Copyright © 2014 American Wood Council. All rights reserved. 10
Framing
Staggered Nailing
Connecting Wood - Philosophy
Wood Structural
Panel
Nail
1/8" GapBetween Panels
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Nailing not staggered Nailing staggeredNailing not staggered Nailing staggered
Splitting occurs parallel to grain
Connecting Wood- Philosophy
Splitting will not occur
Staggering
Staggering a line of
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perpendicular to grain, no matter how close
nails are
gg gnails parallel to wood
grain minimizes splitting
Copyright © 2014 American Wood Council. All rights reserved. 11
Connecting Wood - Philosophy
• Wood, like other hygroscopic materials, moves in varying environments
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Connecting Wood - Philosophy
• Fastener selection is key to connection ductility, strength, performance
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Copyright © 2014 American Wood Council. All rights reserved. 12
Connecting Wood - Philosophy
• Mechanical fasteners
• keep them small
• use lots of them
• Issue is scale of fastener relative to wood member size
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Next...
• Wood connection design philosophy
• Connection behavior
• Serviceability challenges
• Connection hardware and fastening systems
• Connection techniques
• Design software
• Where to get more information
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Copyright © 2014 American Wood Council. All rights reserved. 13
Connection Behavior
• Balance• Strength – L d high strength poor ductilityStrength • Ductility-
Load high strength, poor ductility
good strength, good ductility
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Displacement
low strength, good ductility
Connection Behavior
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Copyright © 2014 American Wood Council. All rights reserved. 14
Connection Behavior
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Connection Behavior
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Copyright © 2014 American Wood Council. All rights reserved. 15
Connection Behavior
Load high strength, poor ductility• Balance• Strength –
Si d b fgood strength, good ductility
low strength, good ductility
• Size and number of fasteners
• Ductility-• Fastener slenderness• Spacing• End distance
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Displacement
Next...
• Wood connection design philosophy
• Connection behavior
• Serviceability challenges
• Connection hardware and fastening systems
• Connection techniques
• Design software
• Where to get more information
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Copyright © 2014 American Wood Council. All rights reserved. 16
Connection Serviceability
Bristlecone Pine
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Giant Sequoia Western Juniper
Connection Serviceability
• Issue: direct water ingress
• Water is absorbed most quickly through wood end grain
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No end caps or flashing
Copyright © 2014 American Wood Council. All rights reserved. 17
Connection Serviceability
• Issue: direct water ingress
• Re-direct the water flow around the connection
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end caps and flashing
Connection Serviceability
• Issue: direct water ingress
• Or, let water out if it gets in...
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Moisture trap -No weep holes
Copyright © 2014 American Wood Council. All rights reserved. 18
Moisture Changes In Wood
Causes dimensional changes perpendicular to graingrain
Growing tree is filled with water
As wood dries, it shrinksperp. to grain
ntia
lly
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Tang
e
Radially
Wood Shrinks
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Woodmagazine.com
Copyright © 2014 American Wood Council. All rights reserved. 19
Connection Serviceability
• Moisture Effects
1% change in dimension for
every 4%
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every 4% change MC
Wet Service Factor, CM
• Dowel-type connectors• bolts
Saturated • drift pins• drift bolts• lag screws• wood screws• nails
Saturated
19% MC
Dry
fabrication MCin-service MC
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CM 1.0 0.7 0.4* Lateral load (*CM=0.7 for D<1/4″)1.0 0.7 1.0 Withdrawal load - lag & wood screws only1.0 0.25 0.25 Withdrawal load - nails & spikes
Dry
Copyright © 2014 American Wood Council. All rights reserved. 20
Wet Service Factor, CM
CCMM = 1.0 if:= 1.0 if:Saturated CCMM 1.0 if: 1.0 if:
1 fastener
2+ fasteners
19% MC
Dry
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CM 0.4 Lateral load (D>1/4″) split splice plates
y
fabrication MCin-service MC Table 10.3.3 footnote 2
Beam to Column
• Full-depth side plates
• may cause splitting
• wood shrinkage
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Copyright © 2014 American Wood Council. All rights reserved. 21
Beam to Column
• Smaller side plates
• transmit force
• allow wood movement
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Beam to Column
• Problem
• shrinkage
• tension perp
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Beam to Wall
• Solution
b l b• bolts near bottom
• minimizes effect of shrinkage
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Slotted hardware
• Avoid contact with cementitious materials
Connection Serviceability
• Beam on Shelf
• prevent contact with concrete
• provide lateral resistance and uplift
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Copyright © 2014 American Wood Council. All rights reserved. 23
Beam to Concrete
• Beam on Wall
• prevent contact with concrete
• provide lateral resistance and uplift
• slotted to allow longitudinal movement
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• typical for sloped beam
Beam to Masonry
• Application
• Application
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Need 1/2” air gap between wood and masonry
Copyright © 2014 American Wood Council. All rights reserved. 24
Column to Base
• Problem
• no weep holes in closed shoe
• moisture entrapped
• decay can result
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Column to Base
• Angle brackets
• anchor bolts in brackets
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Copyright © 2014 American Wood Council. All rights reserved. 25
Column to Base
Where’s the plate?
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Hidden Column Base
• Floor slab poured over connection
• will cause decay
• not recommended
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Column to Base
• Floor slab poured below connection
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Next...
• Wood connection design philosophy
• Connection behavior
• Serviceability challenges
• Connection hardware and fastening systems
• Connection techniques
• Design software
• Where to get more information
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Copyright © 2014 American Wood Council. All rights reserved. 27
Mechanical Connectors
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Traditional Connectors
• All-wood solution
• time tested
• practical
• extreme efficiencies available with computer numeric control (CNC) machining
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www.tfguild.orgwww.timberframe.org
Copyright © 2014 American Wood Council. All rights reserved. 28
• Long History > 100 years
• Uses automated
Traditional Connectors
• Uses automated Computer numerical Control (CNC) milling technology • machine joints• pre-drill holes
• Timber Framer’s Guild -www.tfguild.org
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http://www.tfguild.org/downloads/TFEC-1-2010-with-Commentary.pdf
Traditional Connectors
• Wood dowel connection design technology now available
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Schmidt, R.J. (2006): Timber Pegs – Considerations for Mortise and Tenon Joint Design, Structure Magazine, March 2006, NCSEA, 13(3):44-47. http://www.structuremag.org/wp-content/uploads/2014/09/SF-Timber-Pegs-March-061.pdf
Copyright © 2014 American Wood Council. All rights reserved. 29
Mechanical Connectors
•Common Fasteners• Nails • Staples
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p• Wood Screws• Metal plate
connectors• Lag screws • Bolts
• Included in U.S. design literature
Fastener Values
Fastener Type Reference
B l NDS ER
Evaluation Reports (ER) are developed for proprietary products
Bolts NDS or ER
Lag Screws NDS or ER
Wood Screws NDS or ER
Nails & Spikes NDS or ER
Split Ring Connectors NDS
Shear Plate Connectors NDS
Drift Bolts & Drift Pins NDS
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Metal Plate Connectors ER
Hangers & Framing Anchors
ER
Staples ER
Copyright © 2014 American Wood Council. All rights reserved. 30
NDS Chapter 11 – Dowel-type Fasteners
• ASD and LRFD accommodated through Table 10.3.1
• Bolts
L• Lag screws
• Wood screws
• Nails & spikes
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Fastener Bending Yield Test
Center-Point Bending Test
Load
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Copyright © 2014 American Wood Council. All rights reserved. 31
Dowel Bearing Strength
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Yield Limit Equations
•4 Modes of failure•4 Modes of failure
•6 Yield equations
•Single & double shear
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Copyright © 2014 American Wood Council. All rights reserved. 32
Yield Modes
MODE Ib i d i d•bearing-dominated
yield of wood fibers
MODE II•pivoting of fastener with localized crushing of wood fibers
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Yield Modes
MODE III•fastener yield in b di tbending at one plastic hinge and bearing –dominated yield of wood fibersMODE IV•fastener yield in bending at two
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gplastic hinges and bearing –dominated yield of wood fibers
Copyright © 2014 American Wood Council. All rights reserved. 33
Yield Limit Equations
•4 Modes of failure•6 Yield equationsSi l & d bl h•Single & double shear
•Wood-to-wood•Wood-to-Steel•Wood-to-Concrete
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Yield Limit Equations
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Copyright © 2014 American Wood Council. All rights reserved. 34
Yield Limit Equations
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Chapter 11- Dowels
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Updated TR 12
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http://www.awc.org/publications/TR/index.php
TR 12
• Background and derivation of the mechanics-based approach for calculating lateral connection capacity used in the NDS
• Provides additional flexibility and broader applicability to the NDS provisions. • Simplified Equations
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Copyright © 2014 American Wood Council. All rights reserved. 36
TR 12
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TR 12
Allows for evaluation of ti ithconnections with gaps
between connected members
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Copyright © 2014 American Wood Council. All rights reserved. 37
TR 12
• 2014 Edition - New information on design of• wood members attached to hollow members• design of driven-fasteners with tapered tips• optimizing connections based on location of thre
ads relative to the connection shear plane.
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Chapter 11- Dowels
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Copyright © 2014 American Wood Council. All rights reserved. 38
Chapter 11-Dowels
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Chapter 11-Dowels
Threaded length < lm/4 lm
Dia. Fastener = D
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Dia. Fastener = D
Threaded length < lm/4 lm
Copyright © 2014 American Wood Council. All rights reserved. 39
Chapter 11-Dowels
lm
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Dia. Fastener = Dr
Spacing, End, & Edge Distance 2012 NDS
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Spacing, End, & Edge Distance 2012 NDS
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• Unless special detailing is provided to accommodate cross-grain shrinkage of the wood member.
Spacing, End, & Edge Distance 2012 NDS
• Adds the following notes to 11.5.1 The perpendicular to grain distance between the outermost fasteners shall not e ceed 5" (see Fig e 11H) nless special detailing isexceed 5" (see Figure 11H) unless special detailing is provided to accommodate cross-grain shrinkage of the wood member. For structural glued laminated timber members, the perpendicular to grain distance between the outermost fasteners shall not exceed the limits in Table 11.5.1F, unless special detailing is provided to accommodate cross-grain shrinkage of the member. For
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structural glued laminated timber members, the perpendicular to grain distance between the outermost fasteners shall not exceed the limits in Table 11.5.1F, unless special detailing is provided to accommodate cross-grain shrinkage of the member.
Copyright © 2014 American Wood Council. All rights reserved. 41
Spacing, End, & Edge Distance 2012 NDS
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• Unless special detailing is provided to accommodate cross-grain shrinkage of the wood member.
Local Stresses in Fastener Groups
• 10.1.2 Stresses in Members at Connections
• “Local stresses in connections using multipleLocal stresses in connections using multiple fasteners shall be checked in accordance with principles of engineering mechanics. One method for determining these stresses is provided in Appendix E.”
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Copyright © 2014 American Wood Council. All rights reserved. 42
Local Stresses in Fastener Groups
• Closely spaced fasteners
• brittle failure
• lower capacity
• wood failure mechanisms need
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to be considered in design
Local Stresses in Fastener Groups
• Properly spaced fasteners
• increased ductility
• higher capacity
• spread out the fasteners!
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Copyright © 2014 American Wood Council. All rights reserved. 43
Local Stresses in Fastener Groups
• Appendix E NDS Expressions
– Net tension:
– Row tear-out:
nettNT AFZ ''
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row
i
i
n
iRTRT
viRT
ZZ
tsFnZ
1
''
min''
Local Stresses in Fastener Groups
• Appendix E NDS Expressions
– Group tear-out
• Note: spacing between outer rows of fasteners
netgrouptbottomRTtopRT
GT AFZZ
Z '
'''
22
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• Note: spacing between outer rows of fasteners paralleling the member on a single splice plate <5″
Copyright © 2014 American Wood Council. All rights reserved. 44
Chapter 12 – Split Rings and Shear Plates
• Geometry factor, CD
• Side GrainSide Grain
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Chapter 12 – Split Rings and Shear Plates
• Geometry factor, CD
• End GrainEnd Grain
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Copyright © 2014 American Wood Council. All rights reserved. 45
NDS Chapter 13 – Timber Rivets
• Many applications
• Canada several decades2005 NDS• 2005 NDS• Glued Laminated Timber
• DFL• SP
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• Plates• Steel ASTM A36
H t di d l i d if
Chapter 13- Timber Rivets
• Hot-dipped galvanized if in wet service
• Perforated Steel Plates• Fixed-hole
pattern geometry• Holes sizes lock
and hold rivet to
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and hold rivet to prevent rotation
Copyright © 2014 American Wood Council. All rights reserved. 46
Timber Rivets - Design
• Four strength limit states:
• Rivet yielding
• Pr – parallel to grain
• Qr – perpendicular to grain
• Wood failure
• Pw – parallel to grain
• Qw – perpendicular to grain
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• Plate yielding
• Enhanced ductility
• Lowest value governs design
Timber Rivets – Design 2005 NDS
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Copyright © 2014 American Wood Council. All rights reserved. 47
Timber Rivets – Design 2012 NDS
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Timber Rivets - Design• 2005 NDS
• Reiterative process
Parallel to grain timber rivet capacity• Parallel to grain timber rivet capacity
• Pr = 280 p0.32 nR nC (13.2-1)
• Perpendicular to grain timber rivet capacity
• Qr = 160 p0.32 nR nC
188 2012 NDS
108 2012 NDS
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• Section 13.3.1: ”The maxiumum distance perpendicular to grain between outermost rows of rivets shall be 12”
108 2012 NDS
Copyright © 2014 American Wood Council. All rights reserved. 48
Where to Find Design Examples
•Timber Rivet Connections
• Design Process for a Hanger
Connection
http://www.awc.org/pdf/WDF17-4-rivet-pw.pdf
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Timber Rivets - Design
• Flow chart per the 2005 NDS
• Reiterative process
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Copyright © 2014 American Wood Council. All rights reserved. 49
Design Example – 2005 NDS
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Next...
• Wood connection design philosophy
• Connection behavior
• Serviceability challenges
• Connection hardware and fastening systems
• Connection techniques
• Design software
• Where to get more information
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Copyright © 2014 American Wood Council. All rights reserved. 50
Connection Techniques
• Must evaluate:
• forces present
• environmental effects
• material effects
• aesthetics
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Connection Techniques
• Wood bolts in all-wood structure
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Copyright © 2014 American Wood Council. All rights reserved. 51
Pre-engineered Connectors
• Post to Beam
• Beam to Beam
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Pre-engineered Connectors
• Joist to Beam (Hanger)
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Copyright © 2014 American Wood Council. All rights reserved. 52
Pre-engineered Connectors
• Column Cap & Base hardware
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Pre-engineered Connectors
• Hanger hardware
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Copyright © 2014 American Wood Council. All rights reserved. 53
Pre-engineered Connectors
• Truss hardware
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Custom Hardware
• Difficult situations made easy
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Copyright © 2014 American Wood Council. All rights reserved. 54
Connection Techniques
• Bolts in heavy trusses
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Connection Techniques
• Connecting other frame materials :
• Steel
108
Copyright © 2014 American Wood Council. All rights reserved. 55
Connection Techniques
• Connecting other frame materials :
• Concrete
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Connection Techniques
• Steel bolts in columns
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Hidden kerf plates
Copyright © 2014 American Wood Council. All rights reserved. 56
Connection Techniques
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Connection Techniques
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Copyright © 2014 American Wood Council. All rights reserved. 57
Operations CentreGulf Islands National Park Reserve• Larry McFarland
Architect, V BC
Connection Techniques
Vancouver, BC• CWMM
Consulting Engineers, Inc., Vancouver, BC
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Connection Techniques
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Copyright © 2014 American Wood Council. All rights reserved. 58
•Regional District of Nanaimo Administration Building Expansion
Connection Techniques
•Architect: Neale Staniszkis Doll Adams Architects Vancouver, BC
•Owner; Regional District of Nanaimo Nanaimo, BC
•General Contractor: WindleyC t ti Ltd N i BC
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Contracting Ltd Nanaimo, BC
•Structural Engineer: HeroldEngineering Ltd. Nanaimo, BC
Connection Techniques
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Copyright © 2014 American Wood Council. All rights reserved. 59
Custom Hardware
• A blend of art and technology
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Concealed Connectors
• Proprietary Systems
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Copyright © 2014 American Wood Council. All rights reserved. 60
Concealed Connectors
• Hollow steel connection tubetube
• Expanding cross pins
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Concealed Connectors
• Self-tapping dowel s-w-s
• Threaded screw w-w
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Copyright © 2014 American Wood Council. All rights reserved. 61
•Kwantlen Polytechnic University•Cloverdale Campus
Connection Techniques
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• Bunting Coady Architects, Vancouver, BC• Bush Bohlman & Partners, Inc., Vancouver, BC
Connection Techniques
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Copyright © 2014 American Wood Council. All rights reserved. 62
Connection Techniques
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Concealed Connectors
• Shaped steel shaft
• Steel pins or dowels
• Non-shrink grout
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Copyright © 2014 American Wood Council. All rights reserved. 63
•Raleigh-Durham International Airport
Connection Techniques
• Fentress ArchitectsD CO• Denver, CO
• Washington, DC
• Stewart Engineering, Inc.•Raleigh, NC
• Archer Western Contractors
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•Raleigh, NC
Connection Techniques
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Copyright © 2014 American Wood Council. All rights reserved. 64
Connection Techniques
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Concealed Connectors
• Steel pipe
• Stitch bolts
• Tie-Bolt
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Copyright © 2014 American Wood Council. All rights reserved. 65
Concealed Connectors
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Concealed Connectors
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Copyright © 2014 American Wood Council. All rights reserved. 66
•Arena Stage at the Mead Center for American Theater
Connection Techniques
• Bing Thom Architects• Fast + Epp Structural
Engineers• Clark Construction
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•Arena Stage at the Mead Center for American Theater
Connection Techniques
American Theater
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Copyright © 2014 American Wood Council. All rights reserved. 67
•Richmond Olympic Oval
Connection Techniques
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CANNON DesignGerald Epp, Fast + EppRichmond (south of Vancouver)
•Richmond Olympic Oval
Connection Techniques
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CANNON DesignGerald Epp, Fast + EppRichmond (south of Vancouver)
Copyright © 2014 American Wood Council. All rights reserved. 68
•Myrick Hixon EcoPark Building - WI
Connection Techniques
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Whole Trees Architecture, Stoddard, WI
Next...
• Wood connection design philosophy
• Connection behavior
• Serviceability challenges
• Connection hardware and fastening systems
• Connection techniques
• Design software
• Where to get more information
136
Copyright © 2014 American Wood Council. All rights reserved. 69
•WWPA Lumber Design Suite
B d J i t
Software Solutions Exist
• Beams and Joists• Post and Studs• Wood to Wood
Shear Connections (nails, bolts, wood screws and lag screws)
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http://www2.wwpa.org/TECHGUIDEPAGES/DesignSoftware/tabid/859/Default.aspx
screws)
Connection Calculator
AWC.org
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Copyright © 2014 American Wood Council. All rights reserved. 70
Next...
• Wood connection design philosophy
• Connection behavior
• Serviceability challenges
• Connection hardware and fastening systems
• Connection techniques
• Design software
• Where to get more information
139
More info…
2012 NDS
140
Copyright © 2014 American Wood Council. All rights reserved. 71
More info…
M4 4 Special Design ConsideratiM4.4 Special Design Considerations• Mechanical Connections• Dowel-Type Fasteners• Split Ring and Shear Plates
Connectors• Timber Rivets
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http://www.awc.org/pdf/2012ASD-LRFD_Manual_WEB.pdf
More info???
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2015
Copyright © 2014 American Wood Council. All rights reserved. 72
• Technical papers on Timber rivets: http://www.awc.org/helpoutreach/faq/faqFiles/Timber_rivets.html
More info???
• Timber rivets in structural composite lumber• Simplified analysis of timber rivet connections • Timber rivet connections in U.S. domestic species• Timber Rivets-Structure Magazine• Seismic Behavior of Timber Rivets in Wood Construction• Seismic Performance of Riveted Connections in Heavy Timber
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Se s c e o a ce o eted Co ect o s ea y beConstruction
• Timber rivet suppliers
More info???
• Load-carrying behavior of steel-to-timber dowel connections: http://timber.ce.wsu.edu/Resources/papers/2-4-1.pdf
• New Concealed Connectors Bring More Options for Timber Structures http://www.structuremag.org/Archives/2007-1/p42-43D-Insights-ConcealedConnectorsJan07.pdf
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Copyright © 2014 American Wood Council. All rights reserved. 73
Take Home Messages...
• Transfer loads in compression / bearing whenever possible
• Allow for dimensional changes in the wood due to potential in-service moisture cycling
• Avoid the use of details which induce tension perp stresses in the wood
• Avoid moisture entrapment in connections
• Separate wood from direct contact with masonry or concrete
• Avoid eccentricity in joint details
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Avoid eccentricity in joint details
• Minimize exposure of end grain
Connections
and you…and you thought connecting wood was complicated!
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Copyright © 2014 American Wood Council. All rights reserved. 74
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Questions?
www.awc.org
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