Heavy Timber Decking 2

[nsinma]

I'm looking for allowable unit shear values (for diaphragms)for 3" and 4" tongue & groove decking supported on beams spaced at 6' o.c. There is no plywood topping. Any references would be helpful. Thanks

 

[RARWOOD]

There are no published diaphragm values that I am aware of for T&G timber decking. I heard estimates of 25 #/' to 75#/'. In addition to the low value of deck diaphragms another problem is accurately predicting the deflection.

In the past Oregon State did some testing of using adhesive applied to the tongue and groove of decking to develop diaphragm action. The research was done for Potlatch Corp. for use with Lock-Deck.

Potlatch has since sold their deck line to Disdero Lumber. For more information on glued diaphragms you could contact Disdero, Filler King or any other supplier of laminated deck.

One of the problems you will face in specifing this type of system is that all the past research was based on the use of 3M 5230 adhesive. 5230 is no longer available.

Based on my experience because of the cost of adhesive and the labor cost to apply it, overlaying the deck with plywood or OSB is more econmic.

 

[Taro]

The 2001 NDS wind & seismic supplement gives allowable diaphragm loads for 1" & 2" straight lumber diaphragms. See

http://www.awc.org/pdf/2001WindSeismicSupp.pdf.

You could conservatively use these values for your situation or you could try to calculate capacities by hand.

 

[samdamon]

"Western Woods Use Book" put out by WWPA has allowable shear values for planked diaphragms in Section 10 (Table 10.1 in 4th edition). The values are not for T & G though.

 

[JAE]

Taro - your link didn't work.

 

[jheidt2543]

Taro and JAE, the link works fine if you lop off the "; You" that got attached some how. Here is the correct version

http://www.awc.org/pdf/2001WindSeismicSupp.pdf

 

[RARWOOD]

SamDamon's reply got me thinking a little more about this topic. The WWPA "Western Wood Handbook" is an excellent reference. I aslo found a reference soure that covers glued decking diaphragms. It is "Wood Technology in the Design of Structures" Robert J. Hoyle, Jr. P.E. & Frank E. Woeste, P.E. Fifth Edition Iowa State University Press. I only have copies of the section which deals with Lumber Diaphragms.

A lot of my knowledge on this topic is due to the fact I worked for the Western Wood Products Association for seven years. I added to that knowledge by keeping in touch with their technical department since 1994. If you have further questions on this topic it would be well worth your time to call WWPA.

 

[boo1]

consider looking at WCD 2 - Tongue and Groove Roof Decking

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http://www.awc.org/pdf/wcd2.pdf>