7 Timber Connections

8/12/2019 7 Timber Connections

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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


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


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


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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22 cossin

uu

uuu

qp

qpn

22 cossin

uu

uuu

qp

qpn

22 cos'sin'

'''

uu

uuu

qp

qpn


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


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



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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


Expensive connectionsExpensive connections


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LateralLateral

bracingbracing

Group effectsGroup effects

. and what (not) to do about it.

7 Timber Connections

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