Strength of Wood

[wesdor]

I don't normally visit this part of the site - you guys are way beyond my abilities.

However, I ran into some friends at lunch today.  They are just finishing building a timber frame barn (and are very happy with it).

The beams in the barn are something along the size of 10 x 14 and are made of yellow pine.  The builders told them the yellow pine would be stronger than oak.  We all agree that the builders knew what they were doing, but wonder if anyone can explain why yellow pine would be stronger than the same size oak?

We are guessing it has something to do with the weight of oak vs. pine, but that is just a wild guess.

Thanks for helping educate me.

[beenthere]

The way the design tables are put together, the southern pines can be identified and grouped much easier for the design values (per a certain stress grade). Whereas the oaks cannot be so easily identified as to a specific oak, so all the oaks have to be thrown together. Then the design value for the weakest oak species in the group has to be used.

That is a possibility, but don't know for sure what the builders were talking about. They could, or could not, have any idea what the design values are....so could be seat of the pants, or what they are used to using in buildings.

[ARKANSAWYER]

  In bending red oak and SYP are very close in a green state.  When dry the oak almost doubles in strength in bending.  In compression oak is alot higher then pine.  There is the added weight of oak over pine but it is not really a factor in figuring the support load.   SYP is better then Doug fir and hemlock  and about twice as strong as white pine.  But oak is very hard and and strong.  The problem is getting good size timber clean enough to have good strength.  I work with both alot and like to work green white oak.  But dry pine is easy to cut and fit.

[jim king]

Here are the US Forest service Service reports on the two groups.

http://www2.fpl.fs.fed.us/piper/query/startQuery/357520a5-f92a-4ac6-9a2e-0b9a8166c3ac


http://www2.fpl.fs.fed.us/piper/query/startQuery/357520a5-f92a-4ac6-9a2e-0b9a8166c3ac

This should really confuse the subject.

[Chris Burchfield]

I tried to access it. Looks like you have to be a member.

[SwampDonkey]

Chapter 4 of the "Wood Handbook" might be of some use.

I think you can Google it and have a link come up. If nothing else, maybe a fellow can pick up some information.

[jim king]

wesdor:

I just clicked on the links and they open to the first page.  Just type in the common name and click on submit.

No need for the scientific name or country.