I have been working on a basic software calculator that will take known data points and yield results for several popular risk formulas. I currently have the Bartlett modified formula for strength, and Mattheckâ™s t/R formula.
What other methods or formula do you use? What should be included as part of a structural analysis, in your opinion?
Russ Carlson, RCA
The Wessolly formulae would suggest that t/R is overly conservative without a consideration of wind load and lever arm length.
You could also do Mattheck's "critivcal root plate" ratios and H/D ratios.
The critical root plate is already in a module for root assessment. The H/D would be a good one to add.
In a post in another threat you mentioned this. However, in that context- root loss- the H/D does not mean much. It applies to the probability of breakage in poorly tapered stem, and has little (nothing?) to do with root stability. While an argument might be made that the right taper in the trunk reflects a better developed root system, that is not what Mattheck has reported, and there is no data for North American trees.
Russ Carlson, RCA
[This message was edited by Russ Carlson on Tuesday June 24, 2003 at 10:23 PM.]
BTW are there North Americvan data for t/R? The Bartlett formula is a strength loss formula but I believe Mattheck arrived at his "critical" t/R by observing failed trees.
OK, the strange character set is back along with the missing formatting icons.
I looked at the "Pauli" book which introduces the H/D concept. It is quite unclear about uprooting vs trunk fracture. In fact it uses neither term. It uses "failure" and "fall over." The "archery model" graphics seem to include the roots.
Recall that Mattheck's theories rest on the Axiom of Uniform Stress which suggests to Claus that the tree should be a chain of equally strong links. A good H/D ratio would suggest, I think< that both trunk and root system are well formed.
It does apply to a tree without decay or root disturbanc
I have a Google translated paper from the German original on the Karlsruhe website but I have to reformat it before I can check it out. Claus had submitted H/D papers to ARnoldia (that one was never published) and Arboricultural Journal. Anybody know if the AJ piece was published? MAybe we shouls inquire at UKTC.
What Mattheck is short on mentioning is that AoUS applies to a stabilized tree. Unfortunately, once the tree gorws wood in place, it stays there until it literally rots. And sometimes trees donâ™t respond too quickly or to well to events. So we canâ™t always know if the current condition has been stabilized by AoUS. Thatâ™s a big assumption to make.
I can accept H/D ratios for trunk stability in general, but I think there are too many variables yet to draw conclusions about the root system from it. How many times have we looked at a tree that looks fine, but we know it had a trench cut 8 feet away three years ago, with no sign on the surface. To say it works for natural trees, but maybe not in the landscape makes it useless to me for predicting root stability.
Bear, DE USA
The limitation you describe for "tipping" or "overturning" stability, that is no damage subsequent to natural growth which created the observed H/D ratio, is equally limiting in aeessing trunk resistance to fracture. Mattheck clearly says it is applicable to "undecayed" trees.
H/D is one potentially useful tool in the kit. Usefullness is quite related to the other tools it is used with, most importantly the judgment of judgment of the assessor.
You are quite correct that there may be a lag between any observed conditions and the stimuli they are related to. An example is using Mattheck's "trunk fracture monent" approach to estimating wind load. If a trunk is hollow has the tree adjusted to applied loads with adaptive growth? or it it vulnerable? The associated formulae and questions are in detail in my paper the the Proceedings of the Tree Structure and Biomechanics Conference.
|Powered by Social Strata|