orion
R.I.P.
We've been having somewhat of a structural design discussion under an adjacent thread (cedar strip) and one of the topics closely deals with something I'm working with currently. Given that I have not done much work with wood and the review I've been getting is coming primarily from a Forrest Products handbook and a bit from ANC-18, I'd like to see if someone here has a bit more clarification: When looking at the published values of wood structural properties, there does not seem to be much explanation of what these values are and where they come from. Specifically, I'm pretty sure I'm familiar with most of the testing equipment and procedures however what isn't clear is what do the published numbers represent? More directly to the point, are these values average, median, the lowest, representative of some percentage of a bell curve distribution, or what?
We know for instance that strength properties of wood coupons can vary by as much as forty percent, even when cut from the same part of the trunk, from the same tree and having undergone the same prep process of drying, cutting and finishing. As such, it would be nice to know where the published values came from.
If the characteristics were as consistent as we have for instance with metals, then the question is moot since variations will be relatively minute. For other materials, like composites, we know that the published values represent the minimums of a bell curve range so when someone specifies an "A" or "B" value, it's pretty clear what is being discussed and what the strength values represent.
However to date I have not been able to find the actual specification that is used to arrive at the published values for the wood products. No, I have not had the chance to read the full text of ANC-18 yet (no time to do so at present) so if it's there I would appreciate a page number. Otherwise, if anyone has inside information of the nature of these values, I'd sure appreciate it.
We know for instance that strength properties of wood coupons can vary by as much as forty percent, even when cut from the same part of the trunk, from the same tree and having undergone the same prep process of drying, cutting and finishing. As such, it would be nice to know where the published values came from.
If the characteristics were as consistent as we have for instance with metals, then the question is moot since variations will be relatively minute. For other materials, like composites, we know that the published values represent the minimums of a bell curve range so when someone specifies an "A" or "B" value, it's pretty clear what is being discussed and what the strength values represent.
However to date I have not been able to find the actual specification that is used to arrive at the published values for the wood products. No, I have not had the chance to read the full text of ANC-18 yet (no time to do so at present) so if it's there I would appreciate a page number. Otherwise, if anyone has inside information of the nature of these values, I'd sure appreciate it.
