Some questions about the pulling tests and VTA

[Peter Sterken]

The article is attached here as a pdf-file

The abstract is: Current methods such as the Visual Tree Assessment (VTA) of Mattheck and the pulling tests of Wessolly (SIM) and others will be analysed here. A number of authors have asserted since 1998 that their “generalised tipping curve” (GTC) would predict the uprooting of trees by extrapolating small values of stembase tilt angle under a static pull, and that 100% of the maximum or critical uprooting moment (Mcrit) would be reached at 2.5º. However, evidence elucidated from literature and pulling tests strongly suggest that a very different tipping curve (similar to a curve published in 1965 by a comparatively unknown researcher) has been used instead for the pulling tests, where 1º = 100% Mcrit. That curve will be called the SIM curve herein. A number of related researchers report contradictory findings, by showing either uprooted trees that had obeyed the GTC (0.25º) or trees that had perfectly obeyed the SIM curve (1º) which is confusing. This paper also analyses highly-cited and influential proclamations regarding the GTC and the “dynamic” versus “quasi-static” WLA, that may have, quite simply, sprouted from unconscious research bias.

An analysis of the “generalised tipping curve” of the SIM pulling tests, the “dynamic” SIM wind load analysis and VTA_Peter Sterken.pdf

[Peter Sterken]

The (second version, as the first had somo paragraphs repeated) article is attached here as a pdf-file 🙂

An analysis of the “generalised tipping curve” of the SIM pulling tests, the “dynamic” SIM wind load analysis and VTA_Peter Sterken.pdf

[Khriss]

Well, after viewing last weeks storm damage, i dont see it as much help. Abt half would have passed VTA, but fell. Other half were proper compromised and fell anyway. K

[daltontrees]

On 26/02/2022 at 09:09, Peter Sterken said:

The (second version, as the first had somo paragraphs repeated) article is attached here as a pdf-file 🙂

An analysis of the “generalised tipping curve” of the SIM pulling tests, the “dynamic” SIM wind load analysis and VTA_Peter Sterken.pdf 588.43 kB · 7 downloads

That's goign to take a week to digest.

 

I agree about fallacious reasoning, there's some really dubious ideas that have been embedded in arboriculture that never did pass the test in the first place but have been pushed by their proponents. Dangerous.

[Peter Sterken]

15 hours ago, daltontrees said:

That's goign to take a week to digest.

 

I agree about fallacious reasoning, there's some really dubious ideas that have been embedded in arboriculture that never did pass the test in the first place but have been pushed by their proponents. Dangerous.

I'm glad to hear that, finally 😁

[Peter Sterken]

On 26/02/2022 at 10:40, Khriss said:

Well, after viewing last weeks storm damage, i dont see it as much help. Abt half would have passed VTA, but fell. Other half were proper compromised and fell anyway. K

I think that none of the tree assessment methods work and that their predictive value is close to zero

[Dan Maynard]

I'm old enough to have been studying engineering at university when finite element analysis was quite new. It was drummed into us then that it can be very deceiving because it will give answers which look very good and conclusive even though the whole thing will never be more accurate than your starting assumptions.

 

I don't know much about the GTC MIS theory so have much more reading to do, but on the face of it I am struggling to get past the basic starting point that measuring the strain under load (inclination) tells you much about the stress without knowing the stiffness of the system.

 

I also followed a link to the paper on forks, that is going to take some consideration. Definitely seen a lot of failed forks with included bark, so does that just mean I've seen the result of a failure of natural bracing? Still means that included bark forks are a risky feature.

 

And finally I'd like to add sail area to the list of unproven concepts. Wind loading and turbulence around trees is extremely dynamic, you can see that by the way different parts of the tree are travelling in different directions at the same time, recently climbing ash in 50mph gusts was informative. And all these trees with ivy that are still standing say to me that it's not so simple.