WOOD CONNECTIONS I

Michelle Kam-Biron, S.E. Wood Products Council – WoodWorks!

Continuing Education

Wood Products Council is a Registered Provider with The American Institute of Architects Continuing Education Systems. Credit earned on completion of this program will be reported to CES Records for AIA members. Certificates of Completion for non‐AIA members are available on request.

This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presen‐ tation.

1 Learning Objectives

„Techniques for Efficient, Durable and Structurally Safe Connections „Common Fastener Types „Resources Available

Basic Concepts

Model wood cells as a bundle of straws ƒBundle is very strong parallel to axis of the straws

Compression Parallel to Grain

ƒWood likes compression parallel to grain –makes connecting wood very easy

2 Basic Concepts

Model wood cells as a bundle of straws ƒBundle relatively weak under perpendicular load

Material Properties of Wood

„Splitting happens because wood is relatively weak perpendicular to grain – Nails too close (act like a wedge)

Staggered Nailing

Framing

Wood Structural Panel

Nail

1/8" Gap Between Panels

NailingNailing notnot staggered Nailing Nailing staggered staggered

3 Material Properties of Wood

Splitting occurs parallel to grain

Staggeri ng

Splitting will not occur Staggering a line of nails parallel perpendicular to grain, no to wood grain minimizes splitting matter how close nails are

Material Properties of Wood

„Staggered nailing in tightly nailed shear wall helps prevent sppglitting of framin g

Basic Concepts

Wood and tension perpendicular to grain ƒThe evil of wood connections Initiators: ƒHanging load ƒNotches ƒLarge diameter fastener ƒRestraint by connector detail

4 Hanger to Beam

Load suspended from lower half of beam ƒ Tension perpendicular Split to grain ƒ May cause splits

C

U NA NA T

Hanger to Beam

Full wrap sling option ƒ Load supported in upper half of beam ‰Extended plates puts wood in compression when loaded C

NA NA compression T

Notching

Problem Solution Tension perpendicular to grain

5 Beam to Concrete

Notched beam bearing ƒ Tension perpendicular ƒ May cause splitting ƒ Differential moisture uptake ƒ RldiReseal end grain U Split

Beam to Concrete

Notched Bearing Wall ƒ Alternative to beam notch

Beam to Concrete

Sloped Beam ƒ Not fully supported ƒ May split ƒ Exposed end grain

Split split U

6 Beam to Concrete

Sloped Beam ƒ Notched concrete wall ƒ Alternative to beam notch

Beam to Masonry

„Application • Bearing plate under beam • Prevent contact with masonry

Capillary break

Sawn Lumber Notching

ƒ Outer third of span only ƒ Avoid tension edge

WWPA Technical Note A‐11 “Notching and Boring Guide

7 Possible Reinforcement for an End Notch m 0.9d minimu

Ref. APA Technical Note EWS S560

Field Notching and Drilling of Glued Laminated Timber Beams Tech Note EWS S560

Vertical Holes

Rule of thumb: Strength reduction = 1.5 x Hole diameter/beam width Example: •6” Beam width • 1” diameter vertical hole Reduction = (1.5 x 1”)/6” Reduction = 0.25 Beam is 75% of original strength

APA Tech Note EWS S560

8 Connecting Wood

Wood likes to take on load spread over its surface

U

Connecting Wood

„Mechanical fasteners – Keep ‘em small – Use lots of them – Keep scale of fastener small relative to wood member

Concentrated at a single fastener – wood is more prone to split and crush

9 Connection Techniques

Steel bolts and plates in heavy trusses

Connecting Wood

„A single bolt connecting many members but…wait a minute...

10 Connecting Wood

„Looks can be deceiving...

Connecting Wood Wood, like other materials, moves in varying environments

Connection Serviceability

ƒ Temperature ƒ Humidity and moisture

11 Connection Serviceability

ƒ Temperature ƒ Humidity and moisture ‰Ambient conditions ‰Contact with cementitious materials

Connection Serviceability

Ambient Conditions and wood EMC

USDA Wood Handbook Free download –Forest Products Lab http://www.fpl.fs.fed.us/documnts/fplgtr /fplgtr113/fplgtr113.htm

Moisture Changes In Wood

„Causes dimensional changes perpendicular to grain

Growing As wood tree is dries,it filled with shrinks water perp. to grain

12 Connection Serviceability

„Shrinkage due to moisture loss

Solid Sawn Glulam

Wall Sheathing Sheathing Expands

1/8" spacing APA RATED SHEATHING Filler strip if required

8" minimum clearance

13 Roof Sheathing Expands!

with Moisture NOT Temperature

APA RATED SHEATHING 1/8" spacing

Panel clip or tongue-and- groove edges if required

Beam to Column

Full-depth side plates ƒ May cause splitting ƒ Restrains wood shrinkage U

14 Beam to Column

Smaller side plates ƒ Transmit force ƒ Allow wood movement

Beam Bearing

Slotted connections – Allows for shrinkage and movement under load

15 Beam to Wall

Problem • shrinkage • tension perp U

Beam to Wall

Solution: • allows shrinkage

Slotted hardware

Beam to Beam

Split Beam hangers ƒ Fasteners in top of supported beam ƒ Wood shrinkage ƒ May split ƒ Not recommended Gap Gapunder under U beam

16 Beam to Beam

Beam hangers ƒ Fasteners in bottom of supported beam ƒ Wood shrinkage allowed ƒ Prevents lateral movement

Beam to Beam

Weld bracket ƒ Bucket -style ƒ Dapped support beam

Beam to Beam

Deep Members ƒ Through bolted ƒ Shear plates ƒ Clip angles resist rotation ƒ Allow shrink/swell movement

17 Connecting Wood

Connecting Wood

Split

Split

Connection Serviceability

ƒ Temperature ƒ Humidity and moisture ‰Ambient conditions ‰Contact with cementitious materials

18 Beam to Concrete

Beam on Wall ƒ Prevent contact with concrete ƒ Provide lateral resistance and uplift

Beam to Concrete

Beam on Wall ƒ Prevent contact with concrete ƒ Provide lateral resistance and uplift ƒ Slotted to allow longitudinal movement ƒ Typical for sloped beam

Beam to Masonry Application ƒ Need 1/2” air gap between wood and masonry

U

19 Beam to Masonry

„Application • Bearing plate under beam • Prevent contact with masonry by maintaining ½” space at end of beam.

Column to Base

„Problem – No weep holes in closed shoe – Moisture – Decay U

Column to Base

U Bearing plate Floor slab poured ƒ Anchor bolts in over connection bearing plate ƒ Can cause decay ƒ Slotted column end ƒ Not recommended

20 Column to Base

„ Where’s the plate? „ Grout substituted „ Moisture may wick into wood U

Column to Base

Bearing plate Angle brackets ƒ Anchor bolts in ƒ Anchor bolts in bearing plate bracket ƒ Slotted column end

Arch Base to Support

ISSUE: „ End grain sitting in puddle „ Moisture may wick into wood U

21 Arch Base to Support

Arch Base to Support ƒ Glulam arches with closed shoe

ƒ No provision such as weep holes to remove moisture

Connection Serviceability

Issue: ƒ Direct water ingress ƒ No weep holes U

Arch Base to Support

Good connection ƒ Avoids tension perp ƒ Avoids decay

22 Connection Serviceability

„Issue: direct water ingress Water is absorbed most quickly through wood end grain No end caps U or flas hing

Connection Serviceability

Issue: direct water ingress „ Re-direct the water flow around the connection „ Preservative treated glulam „ End caps and flashing must allow for air flow and drying

end caps and flashing

Summary of Techniques

ƒ Transfer loads in compression bearing whenever possible. ƒ Avoid the use of details that induce tension perpendicular-to-grain stresses in the member. ƒ Multiple fasteners instead of fewer fasteners ƒ Reduce stress concentration ƒ Improve redundancy ƒ Allow for dimensional changes in the wood due to potential in-service moisture cycling. ƒ Avoid moisture entrapment at connections. ƒ Do not place the wood in direct contact with masonry or concrete. ƒ Minimize exposure of end grain.

23 Mechanical Connectors

Common Fasteners • Nails • Staples • Wood Screws • Metal plate connectors • Lag screws • Bolts

Mechanical Connectors

Other types: •Rivets • Split rings • Shear plates • Wood dowels

Mechanical Connectors

24 Small Diameter Fasteners

Nails and nomenclature ƒ Short ƒ Box nail ƒ Ring na il ƒ Common nail ƒ Sinker ƒ Power-driven ƒ Roofing ƒ Etc.

Nail Nomenclature

„ There is no control over nail nomenclature!

„ Manufacturers can and will call fasteners anything that they want.

„ 10d is not a clear specification!

Specifying Nails

Avoid problems by specifying pennyweight, type, diameter and length – Ex: 10d common (0.148” shank dia. X 3” shank length)

25 Connection Techniques

Truss plates ƒDesign metal plate connections using the latest edition of ANSI/TPI 1

Large Fasteners

ƒLag Screws or Lag Bolts ƒ Typically used where bolts can’t ƒ Turned into pre‐ drilled holes

Large Fasteners

ƒLag Screw Connections www. awc.org/pdf/D A1-LagScrew.pdf

26 Large Fasteners

ƒBolts ƒ¼ to 1” dia. X 1”‐16” long (NDS commentary 1” dia. Max.) ƒPre‐drilled holes 1/32 to 1/16” larger ƒCommon mistake is not allowing room for installation

Bolts

• Bolts in wood bearing must be 1 inch or less in diameter • Diameters of 1” and larger can initiate high tension- perp stresses on the bolt hole that induce splitting of the wood

All-Wood Fasteners System

ƒ Long History > 100 years ƒ Uses automated CNC milling technology ƒ machine joints ƒ pre-drill holes ƒ Timber Framer’s Guild - www.tfguild.org

27 Timber Rivets ƒ NDS - Rivets ƒ Hot-Dipped Galvanized ƒ Fixed-shank cross-section ƒ Fixed head dimension ƒ Vary only in length ƒ American Wood Council www. awc. org

ƒ Canada several decades ƒ 2005 NDS ƒ Glued Laminated Timber ƒ DFL ƒ SP

Specialized Connectors

ƒ Split Ring ƒ Wood-to-wood ƒ Require special tooling of wood prior to job site ƒ Shear Plates ƒ Wood-to-dissimilar materials (concrete or steel) ƒ Both have successful long history ƒ Large Glulam or PSL ƒ NDS & AWC

Pre-engineered Connectors

„Joist and beam hangers • Top and face mount • Product specific • Use correct nail • Fill all holes • Ensure proper fastener penetration

28 Pre-engineered Connectors

Hold-down hardware

Codes, Provisions, and Guidance

„Prescriptive „Engineered – Follows a recipe – NDS & NER-272 – CBC, ER, NER reports – Design values – No design values – Accounts for performance of different materials – Nominal value • End use application

29 Codes, Provisions, and Guidance

ICC Reports ƒ NER-272 International Staple, Nail and Tool Association ƒ ESR-1539 International Staple, Nail and Tool Association ISANTA

Codes, Provisions, and Guidance

„CBC & ICC-ES

Codes, Provisions, and Guidance

„National Design Specification for Wood Construction, 2005 Edition (NDS)

30 Basic Theory: Engineered Design

„Nominal Design Values defined by a table in code or NDS. „Nominal Design Values based on equations in the NDS „NilNominal DDiesign VVlalues bbdased on assumed end‐use conditions –Normal Load Duration (10 year) –Dry Condition of Use –No Sustained exposure to elevated temperatures –And others.

Basic Theory: Engineered Design

„For nails, spikes, bolts, lag screws and wood screws – Lateral load design values are calculated by yield‐limit equations – Yield Model – Withdrawal design cappyacity calculated from empirical (test‐based) equations. „Split rings, shear plates, dowels, drift pins, and timber rivets etc. – Lateral and withdrawal design values from empirically based tables.

Connection Behavior

ƒStrength ƒDuctility

31 Mechanical Connections

Basic Type of Connections ƒ Dowel-type fasteners ƒ Bolts, Lag Screws, Wood Screws, Nails/Spikes, Drift bolts, and Drift Pins ƒ Split Ring and Shear Plate Connectors ƒ Timber Rivets ƒ Lateral and Withdrawal Loads.

RESOURCES

Where to get more information

WEBSITES

ƒAmerican Wood Council ‐ www.awc.org ƒAPA –The Engineered Wood ‐ www.apawood.org ƒCanadian Wood Council ‐ www.cwc.ca ƒForest Products Laboratory ‐ www.fpl.fs.fed.us ƒSouthern Pine Council ‐ www.southernpine.com ƒWood Truss Council of America – www.woodtruss.com ƒWoodWorks ‐ www.woodworks.org

32 Where to Find Specifics

„CBC & ICC-ES

Where to Find Specifics

„NDS

Where to Find Specifics

„ The NDS has design provisions

„ Allowable = nominal x adjustment factors

„ Adjustment factors account for a wide range of different end use applications

33 Where to Find Design Examples

NDS Free Download htttp://www.awc.org

Where to Find Design Examples

NDS Free Download htttp://www.awc.org

Where to Find Design Examples

Timber Rivet Connections

34 AWC & WWPA

FREE DOWNLOAD ƒNotching & Boring Guide ƒhttp://www2.wwpa.org/TECHGUIDEPAGES/Literature/tabid /883/Default.aspx ƒTimber Rivet Connections •www.awc.org/pdf/TimberRivetConnections.pdf ƒLag Screw Connections •www.awc.org/pdf/DA1-LagScrew.pdf ƒDowel Equations for Lateral Loads 2001 NDS •www.awc.org/pdf/tr12.pdf ƒToenail Connections •www.awc.org/pdf/DA2-Toenails.pdf ƒPost Frame Ring Shank Nails Connections •www.awc.org/pdf/DA4-RingShank.pdf

For More Information: APA Forms

„Go to www.apawood.org and enter the Publications store „The following publications expand on the information given in this presentation and can be downloaded for free using subject, title, or form number

APA Forms (www.apawood.org)

„ T300 – Glulam connection details „ E830 – Screw and plywood connections „ E825 - Bolt and plywood connections „ D485 – Corrosion resistant fasteners „ TT-035 – Corrosion resistant fasteners „ TT-036 – Glued floors „ TT-039 – Nail withdrawal „ TT-070 – Nail pull through

35 APA Forms (www.apawood.org)

„ TT-045 – Min. nail penetration „ TT-012 – Overdriven fasteners „ TT-056 – Power driven fasteners „ TT-050/051 – Screw withdrawal „ TT-058 – Slant naili ng „ TT-061- Nailing thin flange I-joist „ TT-020 – Dowel bearing strength

Next...

Design software

WWPA Free Downloadable

WWPA Lumber Design Suite ƒ Beams and Joists ƒ Post and Studs ƒ Wood to Wood Shear Connections (nails, bolts, wood screws and lag screws)

http://www2.wwpa.org/TECHGUIDEPAGES/DesignSoftware/tabi d/859/Default.aspx

36 AWC Free Online Calculator

ƒ Single and Double Shear ƒ Withdrawal • Bolts, nails, lag screws and wood screws. ƒ Wood-to-Wood ƒ Wood-to-Concrete ƒ Wood-to-Steel

http://awc.org/calculators/connections/ccstyle.asp

www.APACAD.org

www.WoodUniversity.org

37 AWC Free Online Course

http://www.awc.org/HelpOutreach/eCourses/index.html

AWC Free Online Course

http://www.awc.org/HelpOutreach/eCourses/STD104/STD104eCo urseV11-2007.pdf

Take home messages...

It’s easy to create strong durable wood connections ƒ Avoid the use of details which induce tension perpendicular to grain stresses in the wood ƒ Allow for dimensional changes in the wood due to pottilitential in-serviitliice moisture cycling ƒ Minimize exposure of end grain ƒ Avoid moisture entrapment in connections ƒ Use smaller multiple fastener connections ƒ Multiple resources available to assist.

38 Key to Connections

1. Wood has a strong and weak direction 2. Wood Moves 3. Strive for Consistency 4. Wood and Moisture Don’t Mix 5. Load Path Continuity

Questions???

WoodWorks! Michelle Kam-Biron, S.E. 805.498.4864 [email protected] www.woodworks.org

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