Connection Solutions for Woodframe Structures
Michelle Kam-Biron, PE, SE, SECB
Director of Education
American Wood Council
Copyright Materials
This presentation is protected by US and
International Copyright laws.
laws Reproduction
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.
1
Learning Objectives
• On completion of this course, participants will:
•
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.
•
Be able to describe effects of moisture on wood connections and
implement proper detailing to mitigate issues that may occur.
3
Outline
• Wood connection design
philosophy
• Connection behavior
• Serviceability challenges
• Connection hardware and
fastening systems
• Connection techniques
• Design software
• Where to get more
information
4
Copyright © 2014 American Wood Council. All rights reserved.
2
Outline
• Wood connection design
philosophy
• Connection behavior
• Serviceability issues
• Connection hardware and
fastening systems
• Connection techniques
• Design software
• Where to get more
information
5
Basic Concepts
• Model wood cells as a bundle of straws
• Bundle is very strong parallel to axis of the straws
Parallel
Stronger
Perpendicular
Less strong
6
Copyright © 2014 American Wood Council. All rights reserved.
3
Connecting Wood - Philosophy
• Wood likes compression parallel to grain
• makes connecting wood very easy
7
Connecting Wood - Philosophy
• Wood likes compression parallel to grain
• makes connecting wood very easy
8
Copyright © 2014 American Wood Council. All rights reserved.
4
Connecting Wood - Philosophy
• Wood likes to take on load spread over its surface
9
Concentrated at a single fastener –
wood is more prone to split and crush
Copyright © 2014 American Wood Council. All rights reserved.
5
Connecting Wood - Philosophy
• Wood and tension perpendicular to grain
•
Not recommended
Initiators:
• notches
• large diameter fasteners
• hanging loads
11
Notching
Problem
Solution
12
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6
Beam to Concrete
• Notched Beam Bearing
•
may cause splitting
•
not recommended
Split
13
Beam to Concrete
• Notched Bearing Wall
•
alternate to beam
notch
14
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7
Hanger to Beam
• Load suspended from
lower half of beam
• Tension perpendicular
to grain
• May cause splits
Split
Split

C
N
A
N
A
T
15
Hanger to Beam
Lower half of beam
•
may cause splits
•
not recommended
Exception: light load
Split
•
<100 lbs
•
>24” o.c.
16
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8
Hanger to Beam
Full wrap
sling option
Load supported in upper
half of beam
•
•
Extended plates puts
wood in compression
when loaded
C
compression
N
A
N
A
T
17
Connecting Wood- Philosophy
• Splitting happens because wood is
relatively weak perpendicular to grain
•
Nails too close (act like a wedge)
18
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9
Connecting Wood - Philosophy
Staggered Nailing
Framing
Wood Structural
Panel
Nail
1/8" Gap
Between Panels
Nailing not staggered
Nailing not staggered
Nailing staggered
Nailing staggered
19
Connecting Wood- Philosophy
Splitting occurs parallel to
grain
Staggering
Splitting will not occur
perpendicular to grain,
no matter how close
nails are
Staggering
gg
g a line of
nails parallel to wood
grain minimizes
splitting
20
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10
Connecting Wood - Philosophy
• Wood, like other hygroscopic materials, moves in varying
environments
21
Connecting Wood - Philosophy
• Fastener selection is key to connection ductility, strength,
performance
22
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11
Connecting Wood - Philosophy
• Mechanical fasteners
•
keep them small
•
use lots of them
• Issue is scale of fastener relative to wood member size
23
Next...
• Wood connection design philosophy
• Connection behavior
• Serviceability challenges
• Connection hardware and fastening systems
• Connection techniques
• Design software
• Where to get more information
24
Copyright © 2014 American Wood Council. All rights reserved.
12
Connection Behavior
• Balance
• Strength –
• Ductility-
L d
Load
high strength
strength, poor ductility
good strength, good
ductility
low strength, good ductility
Displacement
25
Connection Behavior
26
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13
Connection Behavior
27
Connection Behavior
28
Copyright © 2014 American Wood Council. All rights reserved.
14
Connection Behavior
• Balance
• Strength –
• Size
Si and
d number
b off
fasteners
• Ductility• Fastener slenderness
• Spacing
• End distance
Load
high strength, poor ductility
good strength, good ductility
low strength, good ductility
Displacement
29
Next...
• Wood connection design philosophy
• Connection behavior
• Serviceability challenges
• Connection hardware and fastening systems
• Connection techniques
• Design software
• Where to get more information
30
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15
Connection Serviceability
Bristlecone Pine
Giant Sequoia
Western Juniper
31
Connection Serviceability
• Issue: direct water ingress
• Water is absorbed most quickly through wood end grain
No end
caps or
flashing
32
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16
Connection Serviceability
• Issue: direct water ingress
• Re-direct the water flow
around the connection
end caps and flashing
33
Connection Serviceability
• Issue: direct water ingress
• Or, let water out if it gets in...
Moisture trap No weep holes
34
Copyright © 2014 American Wood Council. All rights reserved.
17
Moisture Changes In Wood
Causes dimensional changes perpendicular to
grain
Tangentially
Growing
tree is
filled
with
water
As wood
dries, it
shrinks
perp. to
grain
Radially
35
Wood Shrinks
Woodmagazine.com
36
Copyright © 2014 American Wood Council. All rights reserved.
18
Connection Serviceability
• Moisture Effects
1% change in
dimension for
every 4%
change MC
37
Wet Service Factor, CM
• Dowel-type connectors
• bolts
• drift pins
• drift bolts
• lag screws
• wood screws
• nails
Saturated
19% MC
fabrication MC
in-service MC
Dry
CM
1.0
1.0
1.0
0.7
0.7
0.25
0.4* Lateral load (*CM=0.7 for D<1/4″)
1.0 Withdrawal load - lag & wood screws only
0.25 Withdrawal load - nails & spikes
38
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Wet Service Factor, CM
CM = 1.0 if:
Saturated
19% MC
1 fastener
2+ fasteners
Dryy
CM
0.4
Lateral load (D>1/4″) split splice
plates
fabrication MC
in-service MC
Table 10.3.3 footnote 2
39
Beam to Column
• Full-depth side plates
•
may cause splitting
•
wood shrinkage
40
Copyright © 2014 American Wood Council. All rights reserved.
20
Beam to Column
• Smaller side plates
•
transmit force
•
allow wood movement
41
Beam to Column
• Problem
•
shrinkage
•
tension perp
42
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21
Beam to Wall
• Solution
•
b l near bottom
bolts
b
•
minimizes effect of
shrinkage
Slotted hardware
43
Connection Serviceability
• Avoid contact with cementitious materials
• Beam on Shelf
•
prevent contact with
concrete
•
provide lateral
resistance and uplift
44
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22
Beam to Concrete
• Beam on Wall
•
prevent contact with
concrete
•
provide lateral
resistance and uplift
•
slotted to allow
longitudinal movement
•
typical for sloped beam
45
Beam to Masonry
• Application
•
Application
Need 1/2” air gap between
wood and masonry
46
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23
Column to Base
• Problem
•
no weep holes in
closed shoe
•
moisture entrapped
•
decay can result
47
Column to Base
• Angle brackets
•
anchor bolts in
brackets
48
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24
Column to Base
Where’s the plate?
49
Hidden Column Base
• Floor slab poured over
connection
•
will cause decay
•
not recommended
50
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25
Column to Base
• Floor slab poured below
connection
51
Next...
• Wood connection design philosophy
• Connection behavior
• Serviceability challenges
• Connection hardware and fastening systems
• Connection techniques
• Design software
• Where to get more information
52
Copyright © 2014 American Wood Council. All rights reserved.
26
Mechanical Connectors
53
Traditional Connectors
• All-wood solution
• time tested
• practical
• extreme efficiencies
available with computer
numeric control (CNC)
machining
www.tfguild.org
www.timberframe.org
54
Copyright © 2014 American Wood Council. All rights reserved.
27
Traditional Connectors
• Long History > 100
years
• Uses automated
Computer numerical
Control (CNC) milling
technology
• machine joints
• pre-drill holes
• Timber Framer’s Guild www.tfguild.org
http://www.tfguild.org/downloads/T
FEC-1-2010-with-Commentary.pdf
55
Traditional Connectors
• Wood dowel connection design
technology now available
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-March061.pdf
56
Copyright © 2014 American Wood Council. All rights reserved.
28
Mechanical Connectors
•Common Fasteners
• Nails
• Staples
p
• Wood Screws
• Metal plate
connectors
• Lag screws
• Bolts
57
Fastener Values
• Included in U.S. design literature
Fastener Type
Bolts
B
l
Lag Screws
Wood Screws
Nails & Spikes
Split Ring Connectors
Shear Plate Connectors
Drift Bolts & Drift Pins
Metal Plate Connectors
Reference
NDS or ER
NDS or ER
NDS or ER
NDS or ER
NDS
NDS
NDS
ER
Hangers & Framing
Anchors
ER
Staples
ER
Evaluation Reports
(ER) are developed
for proprietary
products
58
Copyright © 2014 American Wood Council. All rights reserved.
29
NDS Chapter 11 – Dowel-type Fasteners
•
ASD and LRFD accommodated through Table 10.3.1
•
Bolts
•
L
Lag
screws
•
Wood screws
•
Nails & spikes
59
Fastener Bending Yield Test
Center-Point Bending Test
Load
60
Copyright © 2014 American Wood Council. All rights reserved.
30
Dowel Bearing Strength
61
Yield Limit Equations
• 4 Modes of failure
• 6 Yield equations
• Single & double shear
62
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31
Yield Modes
MODE I
•bearing-dominated
b i d i
d
yield of wood fibers
MODE II
•pivoting of fastener
with localized crushing
of wood fibers
63
Yield Modes
MODE III
•fastener yield in
b di att one
bending
plastic hinge and
bearing –
dominated yield
of wood fibers
MODE IV
•fastener yield in
bending
g at two
plastic hinges and
bearing –
dominated yield
of wood fibers
64
Copyright © 2014 American Wood Council. All rights reserved.
32
Yield Limit Equations
• 4 Modes of failure
• 6 Yield equations
• Single
Si l & double
d bl shear
h
• Wood-to-wood
• Wood-to-Steel
• Wood-to-Concrete
65
Yield Limit Equations
66
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33
Yield Limit Equations
67
Chapter 11- Dowels
68
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34
Updated TR 12
http://www.awc.org/publications/TR/index.php
69
TR 12
• Background and derivation of the mechanics-ba
sed approach for calculating lateral connection
capacity used in the NDS
• Provides additional flexibility and broader applic
ability to the NDS provisions.
• Simplified Equations
70
Copyright © 2014 American Wood Council. All rights reserved.
35
TR 12
71
TR 12
Allows for evaluation of
connections
ti
with
ith gaps
between connected
members
72
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36
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.
73
Chapter 11- Dowels
74
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37
Chapter 11-Dowels
75
Chapter 11-Dowels
Threaded
length < lm/4
lm
Dia. Fastener = D
Threaded
length < lm/4
lm
Dia. Fastener = D
76
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38
Chapter 11-Dowels
lm
Dia. Fastener = Dr
77
Spacing, End, & Edge Distance 2012 NDS
78
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39
Spacing, End, & Edge Distance 2012 NDS
• Unless special detailing is provided to accommodate
cross-grain shrinkage of the wood member.
79
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
exceed
Figure
e 11H) unless
nless 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
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.
80
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40
Spacing, End, & Edge Distance 2012 NDS
• Unless special detailing is provided to accommodate
cross-grain shrinkage of the wood member.
81
Local Stresses in Fastener Groups
• 10.1.2 Stresses in Members at Connections
•
“Local
Local 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.”
82
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41
Local Stresses in Fastener Groups
• Closely spaced
fasteners
•
brittle failure
•
lower capacity
•
wood failure
mechanisms need
to be considered in
design
83
Local Stresses in Fastener Groups
• Properly spaced fasteners
•
increased ductility
•
higher capacity
•
spread out the
fasteners!
84
Copyright © 2014 American Wood Council. All rights reserved.
42
Local Stresses in Fastener Groups
• Appendix E NDS Expressions
– Net tension:
'
Z NT
 Ft ' Anet
– Row tear-out:
'
Z RT
 ni Fv'tsmin
i
nrow
'
'
Z RT
  Z RT
i
i 1
85
Local Stresses in Fastener Groups
• Appendix E NDS Expressions
– Group tear-out
'
Z GT

'
Z RT
top
2

'
Z RT
bottom
 Ft' Agroup  net
2
• Note: spacing between outer rows of fasteners
paralleling the member on a single splice plate <
5″
86
Copyright © 2014 American Wood Council. All rights reserved.
43
Chapter 12 – Split Rings and Shear Plates
• Geometry factor, CD
•
Side Grain
87
Chapter 12 – Split Rings and Shear Plates
• Geometry factor, CD
•
End Grain
88
Copyright © 2014 American Wood Council. All rights reserved.
44
NDS Chapter 13 – Timber Rivets
• Many applications
• Canada several decades
• 2005 NDS
• Glued Laminated Timber
• DFL
• SP
89
Chapter 13- Timber Rivets
• Plates
• Steel ASTM A36
• Hot-dipped
H t di
d galvanized
l
i d if
in wet service
• Perforated Steel Plates
• Fixed-hole
pattern geometry
• Holes sizes lock
and hold rivet to
prevent rotation
90
Copyright © 2014 American Wood Council. All rights reserved.
45
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
Plate yielding
•
•
•
Enhanced ductility
Lowest value governs design
91
Timber Rivets – Design 2005 NDS
92
Copyright © 2014 American Wood Council. All rights reserved.
46
Timber Rivets – Design 2012 NDS
93
Timber Rivets - Design
• 2005 NDS
•
Reiterative process
•
Parallel to grain timber rivet capacity
•
Pr = 280 p0.32 nR nC
(13.2-1)
188 2012 NDS
Perpendicular to grain timber rivet capacity
•
•
Qr = 160 p0.32 nR nC
108 2012 NDS
•
Section 13.3.1: ”The maxiumum distance perpendicular to
grain between outermost rows of rivets shall be 12”
94
Copyright © 2014 American Wood Council. All rights reserved.
47
Where to Find Design Examples
•Timber Rivet Connections
• Design Process for a Hanger
Connection
http://www.awc.org/pdf/
WDF17-4-rivet-pw.pdf
95
Timber Rivets - Design
• Flow chart per the 2005 NDS
•
Reiterative process
96
Copyright © 2014 American Wood Council. All rights reserved.
48
Design Example – 2005 NDS
97
Next...
• Wood connection design philosophy
• Connection behavior
• Serviceability challenges
• Connection hardware and fastening systems
• Connection techniques
• Design software
• Where to get more information
98
Copyright © 2014 American Wood Council. All rights reserved.
49
Connection Techniques
• Must evaluate:
•
forces present
•
environmental effects
•
material effects
•
aesthetics
99
Connection Techniques
• Wood bolts in all-wood structure
100
Copyright © 2014 American Wood Council. All rights reserved.
50
Pre-engineered Connectors
• Post to Beam
• Beam to Beam
101
Pre-engineered Connectors
• Joist to Beam (Hanger)
102
Copyright © 2014 American Wood Council. All rights reserved.
51
Pre-engineered Connectors
• Column Cap & Base hardware
103
Pre-engineered Connectors
• Hanger hardware
104
Copyright © 2014 American Wood Council. All rights reserved.
52
Pre-engineered Connectors
• Truss hardware
105
Custom Hardware
• Difficult situations made easy
106
Copyright © 2014 American Wood Council. All rights reserved.
53
Connection Techniques
• Bolts in heavy trusses
107
Connection Techniques
• Connecting other frame materials :
•
Steel
108
Copyright © 2014 American Wood Council. All rights reserved.
54
Connection Techniques
• Connecting other frame materials :
•
Concrete
109
Connection Techniques
• Steel bolts in columns
Hidden kerf plates
110
Copyright © 2014 American Wood Council. All rights reserved.
55
Connection Techniques
111
Connection Techniques
112
Copyright © 2014 American Wood Council. All rights reserved.
56
Connection Techniques
• Larry McFarland
Architect,
V
Vancouver,
BC
• CWMM
Consulting
Engineers, Inc.,
Vancouver, BC
Operations Centre
Gulf Islands National Park Reserve
113
Connection Techniques
114
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57
Connection Techniques
•Regional District of Nanaimo
Administration Building Expansion
•Architect: Neale Staniszkis Doll
Adams Architects Vancouver, BC
•Owner; Regional District of
Nanaimo Nanaimo, BC
•General Contractor: Windley
C t ti Ltd Nanaimo,
Contracting
N
i
BC
•Structural Engineer: Herold
Engineering Ltd. Nanaimo, BC
115
Connection Techniques
116
Copyright © 2014 American Wood Council. All rights reserved.
58
Custom Hardware
• A blend of art
and technology
117
Concealed Connectors
• Proprietary Systems
118
Copyright © 2014 American Wood Council. All rights reserved.
59
Concealed Connectors
• Hollow steel
connection
tube
• Expanding
cross pins
119
Concealed Connectors
• Self-tapping
dowel s-w-s
• Threaded screw
w-w
120
Copyright © 2014 American Wood Council. All rights reserved.
60
Connection Techniques
•Kwantlen Polytechnic University
•Cloverdale Campus
• Bunting Coady Architects, Vancouver, BC
• Bush Bohlman & Partners, Inc., Vancouver, BC
121
Connection Techniques
122
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61
Connection Techniques
123
Concealed Connectors
• Shaped steel shaft
• Steel pins or dowels
• Non-shrink grout
124
Copyright © 2014 American Wood Council. All rights reserved.
62
Connection Techniques
•Raleigh-Durham International Airport
• Fentress Architects
• Denver,
D
CO
• Washington, DC
• Stewart Engineering, Inc.
•Raleigh, NC
• Archer Western
Contractors
•Raleigh, NC
125
Connection Techniques
126
Copyright © 2014 American Wood Council. All rights reserved.
63
Connection Techniques
127
Concealed Connectors
• Steel pipe
• Stitch bolts
• Tie-Bolt
128
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64
Concealed Connectors
129
Concealed Connectors
130
Copyright © 2014 American Wood Council. All rights reserved.
65
Connection Techniques
•Arena Stage at the Mead Center for American
Theater
• Bing Thom Architects
• Fast + Epp Structural
Engineers
• Clark Construction
131
Connection Techniques
•Arena Stage at the
Mead Center for
American Theater
132
Copyright © 2014 American Wood Council. All rights reserved.
66
Connection Techniques
•Richmond Olympic Oval
CANNON Design
Gerald Epp, Fast + Epp
Richmond (south of Vancouver)
133
Connection Techniques
•Richmond Olympic Oval
CANNON Design
Gerald Epp, Fast + Epp
Richmond (south of Vancouver)
134
Copyright © 2014 American Wood Council. All rights reserved.
67
Connection Techniques
•Myrick Hixon EcoPark Building - WI
Whole Trees Architecture, Stoddard,
WI
135
Next...
• Wood connection design philosophy
• Connection behavior
• Serviceability challenges
• Connection hardware and fastening systems
• Connection techniques
• Design software
• Where to get more information
136
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68
Software Solutions Exist
•WWPA Lumber Design
Suite
• Beams
B
and
d JJoists
i t
• Post and Studs
• Wood to Wood
Shear Connections
(nails, bolts, wood
screws and lag
screws)
http://www2.wwpa.org/TECHGUIDEPAGES/DesignSoftware/tabi
d/859/Default.aspx
137
Connection Calculator
AWC.org
138
Copyright © 2014 American Wood Council. All rights reserved.
69
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.
70
More info…
M4.4
M4
4 Special Design Considerati
ons
• Mechanical Connections
• Dowel-Type Fasteners
• Split Ring and Shear Plates
Connectors
• Timber Rivets
http://www.awc.org/pdf/2012ASD-LRFD_Manual_WEB.pdf
141
More info???
2015
142
Copyright © 2014 American Wood Council. All rights reserved.
71
More info???
•
Technical papers on Timber rivets:
http://www.awc.org/helpoutreach/faq/faqFiles/Timber_rivets.html
•
•
•
•
•
•
•
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
Se
s c Performance
e o a ce o
of Riveted
eted Co
Connections
ect o s in Heavy
ea y Timber
be
Construction
Timber rivet suppliers
143
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/20071/p42-43D-Insights-ConcealedConnectorsJan07.pdf
144
Copyright © 2014 American Wood Council. All rights reserved.
72
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
• Minimize exposure of end grain
145
Connections
…and
and you
thought
connecting wood
was complicated!
146
Copyright © 2014 American Wood Council. All rights reserved.
73
147
Questions?
www.awc.org
info@awc.org
148
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74