Creating a Continuous Wood Beam by Sistering

• Jul 14, 2006

• #2

RARWOOD

Structural

Jun 17, 2004

519

US

Are you asking how to join double 3 x 10's togther with splices between the supports so they act as a composite sections? If so I don't know of a reliable way to do that. I would be interested in learning more if anyone out there knows of a design method.


I am assuming you want to create an 80' long continous beam with supports every 20'. Why not use treated Southern Pine glulams 6 3/4" x 9 5/8" with no camber spanning 20'? You might even be able to use 40' long glulams. I think though that at 40' that small of glulam might be too flexible out of plane to produce and handle.

With the Southern Pine you could use 26F-V4 material with 2600 Fb. top and bottom.

O

 

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• Jul 18, 2006

• Thread starter
• #3

Corey7320

Structural

Jun 23, 2006

41

I did think of a glulam but none of the manufacturers that i talked to can recommend that glulams be used in a marine environment. Also you'd still need some way to join them continuously. I have also considered sistering three members rather than two and varying splice points so you'd always have 2/3 the strength of the composite member at any required splice. There is also i product i've seen, but don't know the technical name of, that resembles the plates they use for connections on prefab trusses. The product has teeth punched in both directions so you can press two pieces of wood together and transfer shear. I can't find any info online to see what its intended use is though.

 

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• Jul 18, 2006

• #4

SlideRuleEra

Structural

Jun 2, 2003

5,527

US

I gave you the suggestions on using three members in this crossposted thread507-159988

So, rather than continuing there, take a look at page 47 of the TECO Catalog for the spike connectors you mentioned, might work for your application. Here is the link

http://www.clevelandsteel.com/divisions/construction/PDF/Entire_Catalog_print.pdf

Also see the TECO Design Manual at

http://www.clevelandsteel.com/divisions/construction/PDF/Design_Man_Teco_print.pdf

http://www.SlideRuleEra.net

 

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• Jul 21, 2006

• #5

boo1

Mechanical

Oct 31, 2001

2,129

US

SRE is my mentor

 

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• Jul 26, 2006

• Thread starter
• #6

Corey7320

Structural

Jun 23, 2006

41

Based on comments here and some additional reading, i have decided to use a built up section using four 2x12's and varying splice points so the section always has 3 out of 4 2x12's continuous. Also the built up section will have a more consistent treatment throughout the section since larger members get minimal treatment in the center of the section. The 2x12's are also a better grade of wood. I will use stainless screws for building up the member. Does any one know if the treatments used for wood react with certain fastener materials?

 

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• Jul 26, 2006

• #7

SlideRuleEra

Structural

Jun 2, 2003

5,527

US

Hot-Dipped Galvanized and Stainless Steel hardware/fasteners are acceptable for use with commercially available wood preservative treatments such as
ACQ, CA, Borate Compounds, CCA, and Oil Based Preservatives (like as Creosote).

http://www.SlideRuleEra.net

 

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