7 timber connections
TRANSCRIPT
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Timber ConnectionsTimber ConnectionsTimber connectionsTimber connections
Keep in mind:
Wood has a very low tension perpendicular
strength
Wood has a very low shear strength
Compression properties are very favourable
The moral of the story is therefore:
Avoid complex connections, especially those that
induce tension perpendicular and shear stresses
Aim for compression connections as much as
possible
The variety of timber connectionsThe variety of timber connections
steel columns
dimension lumber joists
glulambeams
PSLbeams
Heavy steel bracket
to connect atrium
trusses
riveted heavy steel bracket
toe nailed joistsNailed light metal hangers
Heavy steel
support bracket
Typical Timber Fastener CapacitiesTypical Timber Fastener Capacities
Fastener type Lateral Capacity(parallel to grain)
min. max.
Nails 132 N (30 lb)1 common, SPF
3,000 N (675 lb)6 common, D-Fir
Glulam Rivets 1560 N (351 lb)40 mm, Spruce GL
2,700 N (608 lb)90 mm, D.Fir-L
Lag Screws1540 N (347 lb)
, 70 mm, North
15,100 N (3,400 lb)
, 171 mm, D.Fir
Bolts 2170 N (488 lb), 38 mm, North
21,000 N (4,725 lb)1, 191 mm, D.Fir-L
Split Rings
Shear Plates
12,600 N (2835 lb)2 split ring,
Northern species
36,800 N 8,280 lb4, shear pl., 7/8
bolt, D.Fir-L
TraditionalTraditional
connectionsconnections
Compression structureCompression struc ture
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SimpleSimplebeambeam
supportssupports
Compression
perpendicular to
grain stresses
Assure adequate
bearing area
Beam onBeam on
columncolumn
supportsupport
Use a hardwood block to
reduce bearing stresses
Face mountedFace mounted
beam hangersbeam hangers
with timber rivetswith timber rivets
notch
Compression
perpendicular to
grain
Saddle beam hangersSaddle beam hangers
seat
saddle
BoltedBoltedbeambeam
supportssupports
Support connectionsSupport connections
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HaunchHaunch
connectionsconnections Connection DesignConnection Design
Calculate connection force
Choose fastener type based on
available space
fastener capacity
structural configuration
aesthetics
fastener availability
ductility requirement
Calculate capacity
Connectors loaded at an angle toConnectors loaded at an angle to
the grainthe grain
22
cosQsinP
QPN
rr
rrr
Pr
Qr Nr
Hankinsons Interaction Equation
= 90o = 0o
Nail connectionsNail connections
Nailed t russesNailed t russes Nails and SpikesNails and Spikes
Most common fastener in N. America Widely used in Wood Frame Construction
Easy to install
No pre-drilling (careful splitting!)
Ductile connection - no group effect
Efficient - especially with panel products
Limited by spacing requirements (2 times
crack growth length)
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Connection ConfigurationConnection Configuration
loaded
end distance spacing
edge
distance
row
spacingno. of rows
and other parameters
Bolted connectionsBolted connections
Bolted ConnectionsBolted Connections
Based on ultimate capacity
Quantified by Johansen yield model
Ductility depends on bolt slenderness,
spacing, end distance
Load
Displacement
Slender bolts
Stocky bolts
Brittle failure modesBrittle failure modes
loaded end distance > 7d
(preferably > 10d)
Spacing > 7d
edge distance
> 3d
row spacing
> 3.5d
Similar rules exist for perpendicular
to grain loading
Avoid brittle failure modes by following
spacing rules:
GroupGroup
effectseffects
Auditorium
University of Northern BC
Prince George
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Group effects in bol tedGroup effects in bolted
connectionsconnections
Factor to account for no. of bolts in a row
JG = 0.33 (l/d)0.5 (s/d)0.2 N -0.3 < 1.0
End distance effectEnd distance effect
JL = loaded end distance factor
= 1.0 for e = 10d
= 0.75 for e = 7d
Load
Displacement
e > 10d
e = 10d
e = 7d
Group effects in bol tedGroup effects in bolted
connectionsconnections
Row factor
JR = 1.0 for 1 row
= 0.8 for 2 rows (2 or more bolts in row)
= 0.6 for 3 rows (2 or more bolts in row)
Lag ScrewsLag Screws
Similar to single shear bolt connection
Use Johansen yield model
Penetration length = main member thickness
Also have
substantialwithdrawal
resistance
(Prw)
High strength fasteners
Provide larger grip surface on wood
Wood failure modes typical
Split Rings and Shear PlatesSplit Rings and Shear Plates
shear plates
split ring
Split Rings andSplit Rings and
Shear PlatesShear Plates
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Installation of SplitInstallation of SplitRings and ShearRings and Shear
PlatesPlates
Installation: special tools
tight fit
ideal for pre-
fabrication
Shear plateShear plate
installationinstallation
Load transfer withLoad transfer with
Split Rings and Shear PlatesSplit Rings and Shear PlatesLarge split ringLarge split ring
connectionsconnections
Shear plate connection
Glulam Rivet
connectionsLag screw for
positioning
nalysis of splitnalysis of split
ring connectioning connection
Note: Split rings can carry loads
at different angles to grain. Shear
plates always carry loads in the
same direction as the member load
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Appl ications forAppl ications for
split ringssplit ringsAppl icationsAppl ications
for shearfor shear
platesplates
Example of a shear plateExample of a shear plate
connectionconnectionRidge connection with split ringRidge connection with split ring
Glulam RivetsGlulam Rivets
High strength nailed connection for heavy timber
construction
Special nail
High strength (high capacity)
Oval cross-section (less splitting, tight spacing
Steel side plates(better load distribution)
Wedged head (fixed head, force double curv.)
Beam hangerBeam hangerconnections withconnections with
glulam rivetsglulam rivets
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Glulam Rivet connection geometryGlulam Rivet connection geometry
LP needed for
calculating capacity
OnOn
--site installation of glulam rivetsite installation of glulam rivet
connectionconnection
loaded perpendicular to
grain (V)
loaded parallel to grain (T)
loaded in withdrawal (T) LoadLoad
directionsdirections
seat takes vertical load (V)
T
V
Failure ModeFailure Mode
Erection of Atrium TreesErection of Atrium Trees ErectionErection
of Atriumof Atrium
TrussesTrusses
Steel plates
fastened to PSL
members with
Glulam Rivets
On-site bolted
connection
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Trusses wi th light metal gauge connectorsTrusses with ligh t metal gauge connectors Failure modesFailure modes
1. Teeth pulling out
Nu = nu (KDKSFKT)JH
= 0.6JH is a moment factor for
heel connections
1
slopeSlope JH
< 1 / 4 0.85
> 1 / 4 to 1 / 3 0.8
> 1 / 3 to 1 / 2.4 0.75
> 1 / 2.4 to 1 / 2.2 0.7
> 1 / 2.2 0.65
Failure modesFailure modes
2. Tensile failure of plate
Tr = tp
= 0.6
3. Shear failure of plate
Vr = vp
= 0.6
Calculating tooth resistanceCalculating tooth resistance
Nu and Ns are based on test values
(N/mm2) listed in CCMC reports
Nu = 0.8 (Test value)(Agross)
or
Nu = (Test value) (Anet)
Where Agross is the total area covered by
the truss plate, and Anet is the total area
covered less the end zones as shown in
the next slide
Net areasNet areas
for toothfor tooth
resistanceresistance
a = end distance
= max (12mm or
0.5 tooth length)
e = edge distance
= max (6mm or
0.25 tooth length)
Load DirectionsLoad Directions
nu = pu
nu = qu
nu = pu
nu = qu
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Load DirectionsLoad Directions
22 cossin
uu
uuu
qp
qpn
22 cossin
uu
uuu
qp
qpn
22 cos'sin'
'''
uu
uuu
qp
qpn
Load DirectionsLoad Directions
Interpolate between
nu and nu
Note:
pu , qu , pu and quare given in CCMC
evaluation reports
Slip resistanceSlip resistance
For serviceability limit state (unfactoredloads)
Slip resistance
Nrs = NsKSF
This is calculated similarly to the ultimatestrength
High StrengthHigh Strength
ConnectionsConnections
Oslo Airport, NorwayOslo Airport, Norway
High strength dowel connectionsHigh strength dowel connections
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FieldFieldConnectionConnection
Slotted-in
steel plates
Small tight
fitting dowels
Field installed
dowel
Pedestrian bridge with tightPedestrian bridge with t ight
fitting dowel connectionsfitting dowel connections
Note: only untreated
timber used
Design for durabilityDesign for durability
Roof overhang
Protective sidingLillehammer Olympic Ice Skating arena
(98 m span)
Arched trusses w ith
tight fitting dowel
connections
TheThe bedframebedframe
connectionconnection
a quick solution fora quick solution for
temporary buildingstemporary buildings
TheThe InduoInduo
connectorconnector
Dowel-type connector
Cast steel connector
element
Acc urat e mach ini ng
required
Threaded connection to
other elements
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Grouted dowel connectionGrouted dowel connection
Grouted BVD ConnectionGrouted BVD Connection
Grouted connector installed
Grouted connectors in section
Grouted BVD ConnectionGrouted BVD Connection
BVD Connector typesSection of BVD
Connectors installed
The Delft Tube ConnectorThe Delft Tube Connector
The TubeThe Tube
ConnectorConnector
Expanded tube installed Deformed connector
HighHigh
capacitycapacity
gluedglued--inin --rodrod
connectionconnection
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GluedGlued--in specialtyin specialty
connectorsconnectors
thethe TisCoTisCo
A gr out ed-in tub e
connector
Poly-vinyl-esther
grout, commonly
used for anchoring
into concrete
Threaded
connection to other
elements
A combinat ion ofA combinat ion of
haunched columns andhaunched columns and
underpinned curvedunderpinned curved
beamsbeams
Longspan archLongspan arch
splicesplice
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TransportationTransportationchallengechallenge
High strength connections massHigh strength connections massproducedproduced
Thalkirchen Bridge, Munich
Design for durabilityDesign for durability
LargeLarge
fingerjoints forfingerjoints for
onon--sitesite
connectionsconnections
Expensive connectionsExpensive connections
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LateralLateral
bracingbracing
Group effectsGroup effects
. and what (not) to do about it.