huangyhg

general information on 100+ year old wood
have a situation that i've not really encountered before. i'm looking at an extremely old, and big, barn (approx 125 years old) that thru neglect & poor decisions (stupid contractor alterations) is unstable. the situation i find is that the wood & timbers in this structure are plainly "as hard as a rock". anyone encountered this wood condition before and how did you handle (design stresses, connection repairs, cutting the stuff, etc.)?

petrified?
normally for wood with unknown properties, you can take samples of the wood and test it in a lab for max. tensile strength, or perhaps a beam flexural test....don't know what astm is out there that would apply. but with the test you could then apply a safety factor, perhaps 2, to get an allowable stress to use or correllate with other current types of wood.
i know that the allowable stresses given for wood in the nds specifications use a sf between 1.6 and 2.
thanks for the response but i have a local university that i normally take wood samples to for these type tests and plan to do that. really curious if anyone has seen this condition (really hard - simulated petrified) in existing wood structures before & how did they handle.
i've not seen the hard-as-a-rock type of wood you describe. older woods generally are more dense, but rock-like? hmmm. the only thing i can think of is sometime back i heard a speaker talk about the use of hardwoods from the pacific rim. these woods had stiffnesses and strengths that were much higher than "typical" wood.
another thought....sometimes wood forms are used (with the grain showing) in concrete construction that gives the "look" of wood - are you sure its wood and not concrete?
nope - not concrete. it's wood for sure. i have looked at numerous "older" wood structures and never encountered this condition before. the barn is located in central u.s. (kansas) so don't think the hard wood theory would prevail.
it is prbably because of the drying process it went through right after construction. my guess it may be oak lumber.
jimzpe:
given the time frame and location (can you be more specific on location? there is a lot of difference across kansas.) i would say the wood is cottonwood. it was greensawed on or close to location, and nailed up green. cottonwood takes a nail good when green, but when dryed is damn hard. if you must nail to it, either use tempered cement nails, or predrill slightly undersize. and a big hammer.
100 years ago, the only trees in kansas were along streams, or had just been planted by settlers. heck, it was so desolate they cut fence posts from limestone rock.
another two posibilities could be walnut and locust. locust is extremely hard when dry and can be found along streams and fence rows in western, ok and kansas.

__________________
借用达朗贝尔的名言：前进吧，你会得到信心!
[url="http://www.dimcax.com"]几何尺寸与公差标准[/url]