timber decking

[craigory28]

Does anyone know of a way to get diapragm (w/o using plywood)capability out of timber decking which is running perpendicular to the supports?

 

[dougantholz]

Craigory,
There are a couple of issues that you might consider...first, is this an existing building in which you aren't changing the lateral force on it...I would say that by emperical methods the floor already works as a diaphragm, unless you have evidence the floor is not distributing the loads properly.
Second, you could analyze the decking as small, fixed-fixed beams where the load is distributed over the large number of framing members that make up the deck. This works analytically as long as you have at least two screws into each member.
Try that, or a source you might try is "Structural Renovation of Buildings: Methods, Details, & Design Examples"
by Alexander Newman
This is a pretty good source, we have it in our office and use it quite a bit to evaluate old (100 yrs) buildings for renovation work.

 

[JAE]

Not perpendicular... but check out UBC 1997, Section 2315.3 for diagonally sheathed lumber diaphragms. (UBC 1994 - Section 2314.2)

 

[boo1]

I use diagonal bracing (2x8,10 ect) under the deck to generate the required stiffness. You could also install the decking on an angle.