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.

ben@ftet.com

Speaker email address

This presentation was developed by a third party and is not funded by WoodWorks or the softwood lumber check-off.