Old Wood Framing 2

[SperlingPE]

What do you do to determine engineering values for old wood framing?
Early 20th century wood framing.
Wood floor/roof joists that are actual size (2x12 is 2"x12").
Wood headers/beams.

Will not be doing any on site load testing.
Probably will not do any lab testing of individual pieces.

I have some history of the building and what it was used for.
Nothing in writing concerning the history of the building.
There are no drawings available.

 

[JAE]

For older wood I know my "older" mentors who worked in the 1927 to 1970 range used to use 1000 psi when they didn't know.

I usually stay close to Fb = 800 psi depending on how the wood visually looks to me and if there is visible sagging or moisture exposure.
If the wood looks crappy (a technical term) then I may go to 500.



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[SperlingPE]

Thanks for the information

Wood looks very good.
Building was a farm implement factory.

 

[KootK]

Colleagues of mine have commissioned lumber graders to come out to projects and evaluate. I'm in Canada though. Everybody has a high school buddy who grades lumber now...

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Triangled]

The old wood can be from old growth forests, quite dense, full-sized, tight ringed and strong. I'd feel quite comfortable with JAE's numbers above. If you need more you might get a copy of old codes/wood books. Generally speaking, reflecting on major value changes since the 80s I'd be expecting to see values showing Fv tending to be conservative, Fb is what it is, Ft unconservative.

 

[dcarr82775]

I use Fb values from a 1960's era NDS that is in the office. For DF the lowest is about 1,200psi extending to upwards of 2,000psi for the really good stuff. I have used 1,500psi several times. If you know the history you could back out some presumptive loading (warehouse maybe?) and see what the stresses are.

For some truly gorgeous lumber we have used 2,000psi for bending. They were rough sawn 3x14's 22-ft long, and some were being removed others re-used. The contractor was just throwing some of them away. We grabbed bout 30 of them for a co-workers project. Then he moved so I imagine they are rotting under a tarp somewhere.

 

[JAE]

dcarr - I'd say those numbers are probably pretty good for the lumber used in that day. The concern I always have is that between 1960 and today the wood has possibly experienced long term drying (embrittlement) and in some cases exposure to moisture so I'm not sure I'd be comfortable using numbers as high as the "original" values. But as you say - if you have "really good stuff" perhaps I'm being a bit too conservative.

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[woodman88]

You can get (a free download) the 1944 NDS and 1922 design values here

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.