SIA- the tree pulling test/theory

[treemeup]

Oh, but I must be near the top of the list!

I'll be checking in on this one every now and then, might even comment if I'm feeling brave

[mrtree]

I have been looking for reading materials on this test

 

Checkout

 

Neville Faye's Treework Environmental Practice Website, it has a number of seminars that are summarized. This is a good place to get some very basics about tree pulling.

 

Brudi & Partner website has some articles (Tree Consult) that are well worth reading

 

The book Tree Structure and MEchanics Conference Proceedings: How Trees Stand Up and Fall Down has a number of articles that should be read including Trees and Statics: Nondestructive Failure Analysis

 

This is where I would start learning about tree pulling and statics and then move into the literature citations for more indepth understanding of specific topics.

[mrtree]

There is a "myth" going around that tree pulling test will tell you the safety of the tree and the results are the end of the story. I think there is a great misunderstanding of the use and limitations of the theory.

 

Firstly there are two things the test calculates, tipping safety and breaking safety. These values are not for the tree but rather for the points tested under the conditions layed out in the calculations of safety. Thus the test does not tell us about the strength of crotches, summer limb drop, etc. Further the test does not tell us if the tree will ever fail but rather the safety values under the conditons layed out in the calculations. Thus the wind speed (and thus pressure) used for calulations is an important factor, we do not calculate safety for greater winds speeds and obviously the safety if greater for wind speeds below that speed used for calulations.

 

Pulling test requires that the tree evaluator do a tree risk assessment prior to pulling and identify the areas that require testing. Thus the experienced assessor must find the thinnest shell wall or areas of least solid green wood that are to be tested. I think this is one of the big problems with the application of the test. The test is done by a rather small and select group that believes they have the secret engineering knowledge while many "working" arborist believe they have the understanding of the biological side of the tree.

 

The test is costly and most tree assessors (and tree owners) will need to decide if there is worthwhile information to be gained by a pull test for a specific tree. This in itself demands that the assessor believes that other methods of risk assessment do not, or cannot, give the information necessary and here lies one of the other reasons that there is great friction within the academic tree risk assessment world.

 

Even with a breakage safety and tipping safety calculation the job is not done. What is the disposition of the tree? Is it based on the test alone or do societal values come into play, are there changes to the landscape that will affect the tree, etc. The assessor might take all factors into account and make a decision or they might pass the information along and allow a "supervisor" etc. to make the decision.

[mrtree]

The book Tree Structure and MEchanics Conference Proceedings: How Trees Stand Up and Fall Down available from ISA

 

Trees and Statics: Nondestructive Failure Analysis available here Publications | Urban Forest Innovations

[Tony Croft aka hamadryad]

There is a "myth" going around that tree pulling test will tell you the safety of the tree and the results are the end of the story. I think there is a great misunderstanding of the use and limitations of the theory.

 

 

The test is costly and most tree assessors (and tree owners) will need to decide if there is worthwhile information to be gained by a pull test for a specific tree. This in itself demands that the assessor believes that other methods of risk assessment do not, or cannot, give the information necessary and here lies one of the other reasons that there is great friction within the academic tree risk assessment world.

 

 

I do not believe there to be anything in the test that is of value going on what ive just heard, and having to be VERY careful with my training budget and vacation allowance I think this one will be so far down the list of priorities as to almost never be looked into further... I haven't had the opportunity to ask nev fay why he is such a believer in the test, and my respect for HIM and nobody else involved makes me give it any time at all.

 

It needs time and dedication devoted to this, obviously and right now my time is being consumed in researching the biology of deadwood for my baby/project.

 

but I shall be back at this no doubt, it plagues me, vexes me so!

[mrtree]

It needs time and dedication devoted to this, obviously and right now my time is being consumed in researching the biology of deadwood for my baby/project

 

I think you and many others have to wonder if there tree risk assessments would benefit from this technique and in your case I would definitely suggest your book is more important than you learning about SIA.

 

Just so you know I do not use SIA, I do use SIM, and I have never had a need for SIA as the disposition of most trees I deal with is decided by those that are not going to spend thousands on consultants (for one tree)

[Tony Croft aka hamadryad]

I now have in my possession two AA arb journals,volumes 31 no 3 and 4, i've had a quick scan and that's all i needed.

 

Suffice to say that SIA is not for me, I need a reliable system, and as for the argument that two or three test failures versus none published for the VTA system speaks volumes.

 

The SIA method is very limited in application, VTA is not, VTA is widely practised THE WORLD over by thousands of people so by volume alone the number of assessment is FAR greater in VTA than in SIA so a couple of failures is VERY relevent in SIA, and as far as I am concerned I like to think of claus crying out "see you crazy ba######ds!

 

Im definatley staying well in the VTA side of the fence!

[Paul Barton]

Not knowing much of SIA (I haven't taken the time to read the links, sorry) are VTA and SIA at odds with eachother?

 

Does it make sense to take sides if they approach tree assessment from different angles with different objectives?

 

It seems to me these discussions can quickly turn in to one vs the other e.g. the previous discussions about Thermal imaging and other technologies.

[mrtree]

Suffice to say that SIA is not for me, I need a reliable system, and as for the argument that two or three test failures versus none published for the VTA system speaks volumes.

 

I think this is not quite fair. Any time a tree is removed because a homeowner, judge, municipality etc. does not believe a VTA, that is a failure. Any time a tree is condemned at t/r of <30 that is a failure of the test. Any time a tree fails after being assessed by VTA that is a failure.

 

There is a whole pile of information on the failures of VTA, specifically the problems of t/r. That does not make the system a total lose but it does point to the needs to be trained and educates about VTA and other systems.

[Tony Croft aka hamadryad]

I think this is not quite fair. Any time a tree is removed because a homeowner, judge, municipality etc. does not believe a VTA, that is a failure. Any time a tree is condemned at t/r of <30 that is a failure of the test. Any time a tree fails after being assessed by VTA that is a failure.

 

There is a whole pile of information on the failures of VTA, specifically the problems of t/r. That does not make the system a total lose but it does point to the needs to be trained and educates about VTA and other systems.

 

 

Im not taking sides, im not kind of bloke, what I am doing is making an informed decision and voting with my feet.

 

We are all entitled to that, IMO VTA is based on sound principals, contains a set of dependable principals based on very sound mechanical evaluations. I did a little test and asked my complete inocent brother what he thought of the two basic ideas within five minutes he said "but thats not making any sense to me" and felt far better about the VTA T/R principal than of the SIA one, which cleary indicates that a tree that is in its own example more hollow is safer than one that is less so!

 

its all about the shear.:001_smile: