The VTA Method, lets talk

[Tony Croft aka hamadryad]

When you say

 

"From my perspective much of the criticism of the supporting evidence for tR or some of the other areas of Claus Mattheck's research of don't lead me to devalue VTA or its underlying principles....it does make me suitably dubious about anyone that lays claims to have magic numbers in relation to tree strength or tree "safety".

 

I assume you dont mean Claus as somone? or do you mean like the equation for determining the breaking load of a stem to determin maximum load to pipes or structures etc giving a magic number?

 

as this isnt a magic number but a real number for MAXIMUM force deliverable

[sean freeman]

Magic numbers is a description Claus used when talking about the mathematical relationship between the numbers derived from the fractometer and the material properties of the standing, living tree the last time I was lucky enough to hear him speak back in 2004.

 

Again I think it is a potential trap that over simplification leads you into every time.

[Tony Croft aka hamadryad]

Magic numbers is a description Claus used when talking about the mathematical relationship between the numbers derived from the fractometer and the material properties of the standing, living tree the last time I was lucky enough to hear him speak back in 2004.

 

Again I think it is a potential trap that over simplification leads you into every time.

 

the magic numbers derived from the fracto are just a measure of the residual strength of the part of the wood tested, be that within a decayed/barrier zone, or the sound solid region.

 

numbers that tell us if the wood has normal properties (within a given range) or abnormal, I.E in the case of soft rot and embrittlement. hazard being stifness but not strength.

 

without those numbers we cant evaluate the wood strengths, from the "normal" to the abnormal/hazard value

[sean freeman]

the magic numbers derived from the fracto are just a measure of the residual strength of the part of the wood tested

 

Yes.....I know of an extracted core sample, cut and pulled out of the stem rupturing vascular connection disrupting cell turgour and arguably creating cell laminar shear failures in the process.

 

numbers that tell us if the wood has normal properties (within a given range) or abnormal

 

...and the material properties that these values are being compared to are derived how?

 

Hama, other researchers are very very careful to explain the limitations of applying statistical value sets to individual trees...ie Wessolly et al...the maths matters, just how far you can push the modelling before the values become meanigless matters.

[Tony Croft aka hamadryad]

Yes.....I know of an extracted core sample, cut and pulled out of the stem rupturing vascular connection disrupting cell turgour and arguably creating cell laminar shear failures in the process.

 

 

 

...and the material properties that these values are being compared to are derived how?

 

Hama, other researchers are very very careful to explain the limitations of applying statistical value sets to individual trees...ie Wessolly et al...the maths matters, just how far you can push the modelling before the values become meanigless matters.

 

Hang on!

 

take a core sample from the tree and you have in your hand a VERY real piece of evidence, that will tell you ALL the properties of that section, the viability of barrier zones, the level of decay the volume of the decayed region. I would also assume that the fractometer is a reliable strength test meter!

 

Tables are given at the Back of the updated VTA handbook for various tree species wood strengths!

 

one only has to take a few healthy cores and test them from various trees to ascertain those tables and thier relation to trees within YOUR local stock.

[sean freeman]

Hama, its fine to assume that the compressive and tensile properties of a core sample reveal something more than the properties of that core sample.

 

Tables of material properties of living wood are very difficult to produce empirically without creating enormous caveats and limitations on how the values can be extrapolated hence the importance of Stuttgart table of wood strength (Wessolly and Erb 1998).

[Tony Croft aka hamadryad]

Hama, its fine to assume that the compressive and tensile properties of a core sample reveal something more than the properties of that core sample.

 

Tables of material properties of living wood are very difficult to produce empirically without creating enormous caveats and limitations on how the values can be extrapolated hence the importance of Stuttgart table of wood strength (Wessolly and Erb 1998).

 

So clauses tables are not robust?

 

do you have a link to info on the ones you mention?

[arb culture]

There's a lot of issues in this thread which are going to get lost and confused. Perhaps it would be better to stick to one theory at a time?

 

In response to the core sample question - there is a very real danger that when extracting a core sample you will damage the sample in the process of extraction. Next time you take a core sample have a look at the direction of grain at both ends of the sample, often the sample is twisted - this shows that there is at least some damage to the sample.

 

The precise strength and stiffness of a sample can be greatly influenced by the way in which the sample was obtained.

 

I'm not criticising Mattheck though - his theories and observations are based on sound engineering physics and experimentation. His simplification can be deceptive though. Many of his statements are considerably more complex and insightful than a lot of people at first understand.

 

He also seems to get misquoted quite a lot, as he has been in this thread in few places.

[sean freeman]

There's a lot of issues in this thread which are going to get lost and confused. Perhaps it would be better to stick to one theory at a time?

 

Fair point...I have really only been referring to t/R ratio unease. Perhaps something of a derail from the threads real intention and focus VTA debate....sorry

 

do you have a link to info on the ones you mention?

 

The Stuttgart table of wood strength is published by Wessolly and Erb and forms a major foundation of their SIA approach can be viewed (in part) pages 6 and 7 here http://www2.tree-consult.org/images/pdf/eng/brudi_trees_and_statics.pdf along with a description of how those values were derived.

[arb culture]

Fair point...I have really only been referring to t/R ratio unease. Perhaps something of a derail from the threads real intention and focus VTA debate....sorry. QUOTE]

 

Ooops I did it too.

 

Back to VTA - It's really good.

 

Out of interest, for those people who criticise it, what alternative methods would you use?