How hollow - pull test - stability tests - Wessolly - Brudi - Sterken - Coder

Eric Frei · 28th August 2007, 12:08 AM

Lots of PDf's and documents to read on tree stability testing.

Tree Consult

Also Sterken's PDF well worth the read attached, bit of an extract attached.

Quote:

The safety assessment of hollow trees has always fascinated
arborists, and the criteria to be employed have led in Europe to
severe public discussions in the professional scene.
Based on Mattheck & Breloer (1995), many tree-consultants state
that the necessary thickness of the residual wall should not be below
a t/R ratio of 0,3 to prevent shell-buckling, cross-sectional flattening
and hose pipe-kinking.
Wessolly & Erb (1998) on the other hand publish the opposite theory
by which often much lower thickness is calculated and accepted.
Their methods are based on the bending theory of the hollow beam.
A complete study was made on a 17,1m high eucalyptus tree
(Eucalyptus camaldulensis) in Spain. In accordance with the above
mentioned theory, which is also employed by Wessolly, the
necessary trunk diameter and residual wall thickness where
calculated for different tree-heights.
The results are contrasted throughout the present publication with
criteria regarding torsion, shear, stress peaks, cross-sectional
flattening and shell-buckling.
The above and the study of scientific literature suggest that the truth
lies somewhat in the middle instead of in both extremes.

Eric Frei · 13th January 2009, 05:36 PM

Cool, I loaded up the PDFs. Kenneth James.

Heavy reading though and I haven't really digested it.

Sean Freeman · 13th January 2009, 11:37 PM

The picture that Don Ross posted of the hydro-excavation on one side of a Jacaranda at New Farm is a terrible example of malpractice...it is NOT an example of root crown examination.

Who ever approved the work order for that should have been able to provide the high pressure lance operator with clear instructions on how the work was to be carried out....and they should have ensured that the works were proceeding in the correct manner, in accordance with the specifications given to the contractors.

Hydro-excavation contractors understand how to cut into highly compacted substrates and vaccum up the sludge they create, they do not understand the biological and physical function nor anatomy of tree roots.

That is a very embaressing picture for BCC.

Eric Frei · 14th January 2009, 09:17 PM

Thanks Sean, I missed that picture. I have now embedded it here. It should go over to this thread too, I'll copy these 2 post over to there.
New Farm Jacarandas

Sean Freeman · 28th January 2009, 01:09 AM

Some questions were asked early on in this thread about what impact the Static Integrated Assessment SIA (tree pulling) would have on the roots and soil of the tested tree.

Here is a brief and basic description of the technique that (I hope) will allay any fears about the consequences of carrying out such testing.

SIA is based on methods and research first published by G. Sinn and L. Wessolly back in 1989…it has never been held up as the single perfect method for all cases (in fact it has some strict limitations on how it can be applied) SIA was further refined and the approach refined in papers published by M. Erb and L. Wessolly in 1998.

It is an approach to assessing resistance to loading that is based on the behaviour of mechanical structures and systems used in engineering and the construction industry.

SIA incorporates two techniques;
1) Device supported approach
2) Visual assessment

The device supported approach is the tree pulling….its intention is to measure both the resistance to breaking and the resistance to tipping in the tested tree. It produces very exact data about the reaction of the tree to an artificially imposed load.

The tree has a line with a dynamometer attached (to measure the force applied)
o The change in the length of wood fibres in the outer parts of the stem are measured by an elastometer to 0.001mm over 250mm
o The change of angle of the stem base is measured by an inclinometer to 0.01 degrees

The test runs for approx 5mins, it is non-destructive and should be repeated with the elastometer and inclinometer placed in varying positions to ensure a comprehensive assessment is made.

The second step is the load analysis in the canopy….using a digital camera the canopy shape is drawn the spatial distribution is analysed in comparison to modeling of the wind distribution curve. The following are calculated…
o Centre of gravity of the tree
o Eccentricity of the crown
o Crown sail area
o The moment of wind load (at 32m/sec or force 12)

I do have some reservations about this second step…discussed below

The third step applies knowledge of the material properties of the green wood of the tree that is being tested. Extensive testing was carried out by Erb and Wessolly into the material properties of green wood of a great many of the commonly occurring tree species in northern Europe….this data is contained within the Stuttgart table of wood strength (Erb and Wessolly 1998) and forms the foundation of the calculations required to derive meaningful numerical values to the testing.

So what are the more significant problems with SIA?

• It cannot be used on forest grown trees with shared close canopies
• It is designed only to test whole tree, not individual limibs/unions
• It relies on modeling of drag coefficients through the canopy that are not currently able to represent dynamic resonance and dampening effects in actual trees.
• The baseline data for green wood strength properties does not currently include tropical species native to QLD
• The modeling is not capable of incorporating dynamic growth responses that are not static within the tree…this includes the pathogen host relationship.

Despite these limitations (that the original authors acknowledge) SIA has been used very effectively on individual trees of particular value to the community around them.

But to return to the original question relating to damage to the trees tested only one of the hundreds of trees tested has ever experienced root failure and this particular tree had its roots severed after the pull test.

The forces imparted to the tree are a fraction of the loading that even a minor storm would produce since all that is required is to produce a detectable reading in the two sensors related to a known load, to be able to extrapolate the results using the modelling.

Eric Frei · 26th November 2009, 09:03 PM

We also have some contentious issues to consider here.

Results of tree-pulling (SIM) a possible fraud?

Eric Frei · 10th December 2011, 10:37 AM

Very interesting paper on Root Strength and Tree Anchorage by Coder dated 2010 .... best I've read.

Eric Frei · 21st December 2011, 04:15 PM

PDF attached

Windthrow – a geotechnical engineer’s perspective by Assoc. Prof. Tim Newson 2007

13th January 2009, 11:37 PM	#3
Sean Freeman Monument Status Join Date: Feb 2007 Location: Townsville Nth Queensland & Gold Coast Sth Queensland Posts: 1,985	Re: How hollow - pull test - stability tests - Wessolly - Brudi The picture that Don Ross posted of the hydro-excavation on one side of a Jacaranda at New Farm is a terrible example of malpractice...it is NOT an example of root crown examination. Who ever approved the work order for that should have been able to provide the high pressure lance operator with clear instructions on how the work was to be carried out....and they should have ensured that the works were proceeding in the correct manner, in accordance with the specifications given to the contractors. Hydro-excavation contractors understand how to cut into highly compacted substrates and vaccum up the sludge they create, they do not understand the biological and physical function nor anatomy of tree roots. That is a very embaressing picture for BCC.

14th January 2009, 09:17 PM	#4
Eric Frei Admin - Razor sharp and independent 2 X Diploma Level 5 qualified arborist Join Date: Jan 2007 Location: Brisbane Posts: 12,814	Re: How hollow - pull test - stability tests - Wessolly - Brudi Thanks Sean, I missed that picture. I have now embedded it here. It should go over to this thread too, I'll copy these 2 post over to there. New Farm Jacarandas Attached Thumbnails __________________ Protect your rights to work - Join Australian Tree Association My businesses:- Qualified Brisbane Tree Lopping \| Stump Grinding Brisbane \| Brisbane - Gold Coast Consulting Arborist

28th January 2009, 01:09 AM	#5
Sean Freeman Monument Status Join Date: Feb 2007 Location: Townsville Nth Queensland & Gold Coast Sth Queensland Posts: 1,985	Re: How hollow - pull test - stability tests - Wessolly - Brudi Some questions were asked early on in this thread about what impact the Static Integrated Assessment SIA (tree pulling) would have on the roots and soil of the tested tree. Here is a brief and basic description of the technique that (I hope) will allay any fears about the consequences of carrying out such testing. SIA is based on methods and research first published by G. Sinn and L. Wessolly back in 1989…it has never been held up as the single perfect method for all cases (in fact it has some strict limitations on how it can be applied) SIA was further refined and the approach refined in papers published by M. Erb and L. Wessolly in 1998. It is an approach to assessing resistance to loading that is based on the behaviour of mechanical structures and systems used in engineering and the construction industry. SIA incorporates two techniques; 1) Device supported approach 2) Visual assessment The device supported approach is the tree pulling….its intention is to measure both the resistance to breaking and the resistance to tipping in the tested tree. It produces very exact data about the reaction of the tree to an artificially imposed load. The tree has a line with a dynamometer attached (to measure the force applied) o The change in the length of wood fibres in the outer parts of the stem are measured by an elastometer to 0.001mm over 250mm o The change of angle of the stem base is measured by an inclinometer to 0.01 degrees The test runs for approx 5mins, it is non-destructive and should be repeated with the elastometer and inclinometer placed in varying positions to ensure a comprehensive assessment is made. The second step is the load analysis in the canopy….using a digital camera the canopy shape is drawn the spatial distribution is analysed in comparison to modeling of the wind distribution curve. The following are calculated… o Centre of gravity of the tree o Eccentricity of the crown o Crown sail area o The moment of wind load (at 32m/sec or force 12) I do have some reservations about this second step…discussed below The third step applies knowledge of the material properties of the green wood of the tree that is being tested. Extensive testing was carried out by Erb and Wessolly into the material properties of green wood of a great many of the commonly occurring tree species in northern Europe….this data is contained within the Stuttgart table of wood strength (Erb and Wessolly 1998) and forms the foundation of the calculations required to derive meaningful numerical values to the testing. So what are the more significant problems with SIA? • It cannot be used on forest grown trees with shared close canopies • It is designed only to test whole tree, not individual limibs/unions • It relies on modeling of drag coefficients through the canopy that are not currently able to represent dynamic resonance and dampening effects in actual trees. • The baseline data for green wood strength properties does not currently include tropical species native to QLD • The modeling is not capable of incorporating dynamic growth responses that are not static within the tree…this includes the pathogen host relationship. Despite these limitations (that the original authors acknowledge) SIA has been used very effectively on individual trees of particular value to the community around them. But to return to the original question relating to damage to the trees tested only one of the hundreds of trees tested has ever experienced root failure and this particular tree had its roots severed after the pull test. The forces imparted to the tree are a fraction of the loading that even a minor storm would produce since all that is required is to produce a detectable reading in the two sensors related to a known load, to be able to extrapolate the results using the modelling. Attached Thumbnails

26th November 2009, 09:03 PM	#6
Eric Frei Admin - Razor sharp and independent 2 X Diploma Level 5 qualified arborist Join Date: Jan 2007 Location: Brisbane Posts: 12,814	Re: How hollow - pull test - stability tests - Wessolly - Brudi We also have some contentious issues to consider here. Results of tree-pulling (SIM) a possible fraud? __________________ Protect your rights to work - Join Australian Tree Association My businesses:- Qualified Brisbane Tree Lopping \| Stump Grinding Brisbane \| Brisbane - Gold Coast Consulting Arborist

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