the application of traditional and modern heavy timber connections
TRANSCRIPT
The Application of Traditional and Modern Heavy Timber Connections
Presented: Atlanta, GA – 4MAR15
By: R.L. “Ben” Brungraber, Ph.D., P.E.
This presentation was developed by a third party and is not funded by WoodWorks or the softwood lumber check-off.
“The Wood Products Council” is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES), Provider #G516.
Credit(s) earned on completion of this course will be reported to AIA CES for AIA members. Certificates of Completion for both AIA members and non-AIA members are available upon request.
This course is registered with 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 ofhandling, using, distributing, or dealing in any material or product.
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Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.
Course Description
The selection of heavy timber connections can be challenging, even for designers experienced with these types of building projects. This presentation will provide a thorough discussion of traditional and modern heavy timber connectors and connections, including their design and application. Topics will include some of the connection types and methods used to repair or reinforce existing heavy timber members, such as wooden pegs, wooden wedges, and fully-threaded screws. Discussion will also include a review of European connectors and their selection for specific design applications including cross laminated timber.
Learning Objectives
1. Discuss traditional heavy timber connections.
2. Discuss modern timber connectors and determine how to choose among the various types and makes, depending on specific application.
3. Demonstrate how fully-threaded screws, wooden pegs and wooden wedges can be used to repair or reinforce existing timber members
4. Discuss the applicability of these connectors to Cross Laminated Timber components, including costs (design, fabrication, and installation)
Reinforcing 100’ Span, Northern PA; c. 1973
50 Foot Town Lattice Pedestrian Bridge; c. 1980
144 Foot Town Lattice; Guelph, Ontario c. 1992
Pegged Mortise and Tenon Connections
And “Doctor Joint”
STRUCTURES =“Connections, Held Together by Members”
Tough Connections; Immediately Snug and Sharing Loads
Semi-Rigid Connections – Spring Constants
The “Bent Buster”
2” Diameter Oak Peg in 10,000 pounds of Double Shear
11.1.7 Other Dowel-Type Fasteners
When fastener type or connection fabrication and assembly requirements vary from those specified in 11.1.2, 11.1.3, 11.1.4, 11.1.5 and 11.1.6, provisions of 11.3 shall be permitted to be used in calculation of nominal lateral design values provided allowance is made to account for such variation. Edge distances, end distances and spacing shall be sufficient to prevent splitting of the wood.
- National Design Specification for Wood Construction 2001 Edition
Still Testing Joinery – Among Other Things
Traditional Joinery is Non-Magnetic
Through Splines,
Or
“Free Tenons”
Spline Alchemy @ Building Envelope
End Wall Splines and Large “Bed Bolts”
CNC-Enabled Joinery
a
h
Notched beam – variation dove tail
A Great CNC-Cut Elliptical Dovetail Shear Connection
A Semi- Great CNC-Cut Cylindrical Shear Connection
Wedges, Through-Splines and Cantilevers
Through Splines in Tension
We Are Professionals, ……
3 -Pegged Through Spline
4-Pegged Through Spline
6-Pegged Through Spline
Dog-Leg Splines; Moment Capacity
Repairs with Pegs and Wedges
Sheared Fish Splice Plates
Shear Blocks to Transfer Tension Around Splices
Failed Tension Chord
Deteriorated Truss Verticals
Really Deteriorated Truss Verticals
Early Steel in Joinery - Limited Mostly by Cost
Steel-Assisted Connection Techniques
Custom Castings – for the Truly Obsessed
Transitions in Joinery & Materials
Past AND Future Joinery Methods?
Modern Timber Screws
Thread Variations Picture: Prof. Blass, Uibel, University Karlsruhe
The Latest Great Innovation – Fully Threaded Screws
Modern Timber Screws
Shear vs. Withdrawal
This is the Big Deal•Stronger•Stiffer•No Predrilling Angst•(CAN get it backward)
HeadVariation in Head Design Picture: Prof. Blass, Uibel, University Karlsruhe
No Pre-Drilling & Easily ReplacedEasily Concealed (and one end only)No Separate Washers„Tough“ Response to Load; Axial and ShearInnate Fire ResistanceMinimal Group Action Response and Angle with Grain Differences
Point DesignVariation in points Picture: Prof. Blass, Uibel, University Karlsruhe
Repair and Reinforce (“Preemptive Repair”)
• Near-Miraculous Repair Work• Reinforcing Connections
Alloys, Coatings, and Drivers Vary, too.
Really Long Screws
Classic Repairs & Reinforcements
•Tension Perpendicular•Notches•Openings•Bolted Joints•Bearing Compression•Inducing Composite Action
•Design Guides•White Papers•Code Approvals•Examples•Manufacturers WANT to make these screws easy to use/buy
•The Screws offer AXIAL; more than SHEAR
•“Moment Capacity” if not “Moment Connections”
The screws can work well in Compression, as well as in Tension
Truss Repair
The Miracle Working Screw SFS WTS
Cost more to repair, than to build it wrong, the first time. Way More.
Steel Plated Timber Trusses can so Easily go Awry
Scissors Trusses
• Lots of Axial Tension/Compression Changing Hands at Eaves•“The Crux’ Connection – the Vertical is Critical
Clasping King Posts
Scissors as Wall Framing – Innately Stable
Connection Reinforcement
Mechanically-Induced Composite Action(Joe Miller, “Doctor Slip”)Not as Good as Glue, but less messy and more reliable
Curved Timbers – Repair and Reinforce
Great Custom Glue-Laminated Curves, But ….
Nothing Beats a Post
Or Ten Posts
Disorienting Anachronism - Material and Technique
My First CLT Sighting – Austria; late 20th Century
Gordon Pierce, Home of Austrian CLT
Walnut Creek, California - 2007
CLT as Expressed Shear Wall
Expressed StructureBenson Woodworking
CLT INSTALLATIONStaging Area is a Very Big DealSteady Crew and Crane GuySmall and Steady CrewPlanned Gaps at Butt JointsShipping Container EconomicsEasily Modified – But Still Heavy
Disentangling Systems from Structure
Not All Progress is Good Progress
REALLY? Really
Questions?
This concludes The American Institute of Architects Continuing Education Systems Course
R.L. “Ben” Brungraber, Ph.D., P.E.
Speaker email address
This presentation was developed by a third party and is not funded by WoodWorks or the softwood lumber check-off.