CIVL439 / WOOD476
2003
Timber Connection s Timber Connection
Timber connections Timber
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 conn ections dimension lumber joists Nailed light metal hangers hangers
Typical Timber Fastener Capacities Fastener type
toe nailed joists
Nails
Lateral Capacity (parallel to grain)
min.
max.
132 N (30 lb) 1” common, SPF
3,000 N (675 lb) 6” common, D-Fir
1560 N (351 lb) 40 mm, Spruce GL
2,700 N (608 lb) 90 mm, D.Fir-L
g lulam beams
Glulam Rivets
Heavy steel m s support bracket P S L b e a
Lag Screws
1540 N (347 lb) ¼”, 70 mm, North
15,100 N (3,400 lb) ¾”, 171 mm, D.Fir
Bolts
2170 N (488 lb) ½”, 38 mm, North
21,000 N (4,725 lb) 1”, 191 mm, D.Fir-L
12,600 N (2835 lb) 2 ½” split ring, Northern species
36,800 N 8,280 lb 4”, shear pl., 7/8” bolt, D.Fir-L
Heavy steel bracket to connect atrium trusses
riveted heavy steel bracket
Split Rings Shear Plates
steel columns
Compression struc Compression structture ure
Traditional connections
CIVL439 / WOOD476
An anc ien t t ru ss br id ge r esem bl in g an arc h structure made primary from wooden logs, which are very difficul t to connect for tension loads
2003
Complex Complex timber timber node node with with simple connections
Compression connections
Compression connection for tension members
Compression connections
The connector -less connection
CIVL439 / WOOD476
2003
Simple beam supports
Beam on column support
Use a hardwood block to reduce bearing stresses
Compression perpendicular to grain stresses Assure adequate bearing area
Saddle beam hangers
saddle notch Compression perpendicular to grain seat
Face mou nted beam angers beam hhangers with timber timb er rivets rivets
Support connections Bolted beam supports
CIVL439 / WOOD476
2003
Haunch connections
Connection Design
Calculate connection force
Choose fastener type based on • available space • fastener capacity • structural configuration • aesthetics • fastener availability • ductility requirement
Calculate capacity
Connectors lo aded at an angle to the grain θ
= 0o
θ
= 90o
Pr
θ
Qr
Nr
Hankinson’s Interaction Equation
N r
Pr Qr 2
2
Pr sin Qr cos
Nail connections
Nailed t russes
Nails 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)
CIVL439 / WOOD476
2003
Connection Configuration Configuration loaded end distance
Bolted connections
spacing
edge distance row spacing
no. of rows
…and other parameters
Bolted Connections
Based on ultimate capacity
Quantified by Johansen yield model
Ductility depends on bolt slenderness, spacing, end distance Load
Slender bolts Stocky bolts Displacement
Brittle failure modes
Group effects
Avoid brittle failure modes by following spacing rules: loaded end distance > 7d (preferably > 10d)
Spacing > 7d
edge distance > 3d row spacing > 3.5d Similar rules exist for perpendicular to grain loading
Auditorium University of Northern BC Prince George
CIVL439 / WOOD476
2003
Group effects iin bolted n bol ted connections Factor to account for no. of bolts in a row
End distance dist ance effect effect JL
= loaded end distance factor
JG = 0.33 (l/d)0.5 (s/d)0.2 N -0.3 < 1.0
= 1.0 for e = 10d = 0.75 for e = 7d Load
e > 10d e = 10d
Displacement
e = 7d
Group effects iin n bolt ed bol ted connections Row factor
JR
Lag Screws
Similar to single shear bolt connection
Use Johansen yield model • Penetration length = main member thickness
= 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)
Also have substantial withdrawal resistance (Prw)
Split Rings Rings and and Shear Shear Plates Plates
High strength fasteners • Provide larger grip surface on wood
Wood failure modes typical
shear plates
split ring
Split Rings and Shear Plates
CIVL439 / WOOD476
2003
Installation of Split Rings and Shear Plates Plates
Installation: • special tools
Shear plate installation
• tight fit • ideal for prefabrication
Load transfer with Split Rings and Shear Plates
Shear plate connection
Large split ring connections
nalysis of split ing connection ring
Note: Split rings can carry loads at different angles to grain. Shear plates always carry loads in the same direction as the member load
Glulam Rivet connections
Lag screw for positioning
CIVL439 / WOOD476
2003
Ap pl ic ation or Appl ati on s ffor split rings
Example of a shear plat e pl ate connection
Ap pl ic ati on s Appl ation for sh ear shear plates
Ridge connection with split ring
Glulam 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 hanger connections with glulam rivets
CIVL439 / WOOD476
2003
Glulam Rivet conn ection geometry
OnOn-site installation of glulam glulam rivet connection
LP needed for calculating capacity
Failur e Mode T
loaded perpendicular to grain (V)
V
loaded parallel to grain (T) seat takes vertical load (V) loaded in withdrawal (T)
Load directions
Erectio n of At rium Trees
Erection of Atrium Trusses
Steel plates fastened to PSL members with Glulam Rivets On-site bolted connection
CIVL439 / WOOD476
2003
Trusses wi with th ligh lightt metal gauge connectors
Failur e modes 1. Teeth pulling out Nu = φ n u (K DK SFK T)J H
= 0.6 JH is a moment factor for heel connections φ
Failur e modes
3. Shear failure of plate
φ
0.8 0.75
> 1 / 2.4 to 1 / 2.2
0.7
> 1 / 2.2
0.65
Nu = 0.8 (Test v alue)(Agross ) or Nu = (Test value) (Anet )
= 0.6
φ
> 1 / 4 to 1 / 3 > 1 / 3 to 1 / 2.4
slope 1
Nu and Ns are based on test values (N/mm2) listed in CCMC reports
Tr = φ t p
Vr =
JH 0.85
Calculating tooth resistance
2. Tensile failure of plate
φ
Slope <1/4
Where Agross is the total area covered by the truss plate, and A net is the total area covered less the end zones as shown in the next slide
vp
= 0.6
Load Directions Direction s
Net areas areas for tooth resistance n u = qu
n’ u = q’ u
a = end distance = max (12mm or 0.5 tooth length) e = edge distance = max (6mm or 0.25 tooth length)
nu = pu
n’ u = p’ u
CIVL439 / WOOD476
2003
Load Directions
Load Directions
Interpolate betw een n u and n’ u nu
nu
pu qu pu sin 2 qu cos2
pu qu 2
2
pu sin qu cos
n'u
p 'u q 'u
Note: p u , q u , p’ u and q’ u are given in CCMC evaluation reports
2
p 'u sin q'u cos 2
Slip resistance For serviceability limit state ( unfactored loads)
High Strength Connections
Slip resistance Nrs = Ns K SF This is calculated similarly to the ultimate strength Oslo Airport, Norway
High strength dowel connections
CIVL439 / WOOD476
2003
Pedestrian bridge with ttight ight fitting dowel connections
Field Connection Slotted-in steel plates
Field installed dowel
Small tight fitting dowels
Note: only untreated timber used
Design fo forr durability Roof overhang
Ar ch ed tru ss es w it h tight fitting dowel connections
Protective siding
Lillehammer Olympic Ice Skating arena (98 m span)
The “ bedframe” bedframe” connection
The “ Induo” Induo” connector
a quick solution for temporary buildings
• • • •
Dowel-type connector Cast steel connector element Acc urat e mach ini ng required Threaded connection to other elements
CIVL439 / WOOD476
2003
Grouted BVD Connection
Grouted connector installed
Grouted dowel connection
Grouted BVD Connectio n Connection
BVD Connector types
Grouted connectors in section
The Delft Tube Connector
Section of BVD Connectors installed
The Tube Connector
Expanded tube installed
Deformed connector
High capacity gluedglued-in -rod connection
CIVL439 / WOOD476
2003
GluedGlued-in specialty connectors the “ TisCo” TisCo”
• •
•
A gr out ed-in tub e connector Poly-vinyl-esther grout, commonly used for anchoring into concrete Threaded connection to other elements
A c om bi nat io n o f haunched columns and underpinned curved beams
Longspan arch splice
CIVL439 / WOOD476
Transportation challenge
2003
High strength connections mass produced
Thalkirchen Bridge, Munich
Design for durability
Expensive connections
Large fingerjoints for on -site connections
CIVL439 / WOOD476
2003
Group effects
Lateral bracing
…. and what (not) to do about it.
