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Evaluation
of the Load-bearing Capacity of
Temporary Anchor Points in Living Trees Hyland
R. Johns Grant # 06-HJ-05
Andreas Detter, Brudi & Partner TreeConsult
Failure of temporary anchor points in a tree
is one of the major risks faced by practical arborists. Yet,
little is known about required minimum diameters of limbs and
branches when subjected to loads generated from climbing and
dismantling trees. The research project is set out to perform
on-site winching tests to fracture branches and limbs of different
diameters. The following mechanical properties can be determined:
stiffness, elastic limit and modulus of rupture. The results
shall be complemented with tests under lab conditions on specimens
cut from live limbs.
The study will aid to specify the strength
of branches and limbs that serve as anchor points during tree
climbing and rigging operations. This may also be of interest
to other applications within the arboricultural industry, such
as snow and ice damages, summer branch drop, crown support systems,
leisure structures like canopy walks, challenge courses, tree
houses.
TREE Fund Grant Programs
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Evaluation
of Current Rigging and Dismantling Practices used in Arboriculture
HSE Research Project No. T/6266
Brudi & Partner TreeConsult and Treevolution, UK, with P.
Howard, ArBO, and C. Cowell, Treepartner
In the scope of this research project the British
Health and Safety Executive (HSE) requests to determine best
practice in: -
- carrying out risk assessments prior to dismantling
- planning and organising rigging operations
- selecting measures to prevent accidents
- choosing appropriate work equipment
- assessing the factors of safety in rigging scenarios
Therefore, the contractors will evaluate
and define rigging techniques. They shall collect information
on the working load limit of equippment used, the strength of
temporary anchor points and loads generated from rigging operations.
The results are intended to serve as a source of information
for the prospective guide to safe rigging practice. The project
terminates October 2007. The final report will be published
online shortly after at the
HSE publications website.
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Kinematics
and Dynamics of Tree Dismantling Operations Simulated under
Lab Conditions
Feasibility Study for Prospective Research Projects
Brudi & Partner TreeConsult in cooperation with Prof. Dr.
K. Schneider, University of the Federal Army Neubiberg, Dr.
N. Praxl, DeMotu, P. Howard and O. Campaña, ArBO.
Motion capture and high resolution strain gauge
techniques were applied to evaluate: -
- the kinematics of a section rigged off a vertical trunk
- peak loads generated from dismantling operations
- the dissipation of energy in rigging system and tree
- stem bending and sway caused by snubbing off a log
- kinematics of the climber's body positioned at the stem
Two different notch configurations were
tested against each other. Shock loads generated in the rigging
system were measured and compared to kinematic calculations.
Strain in the stems marginal fibres was used to determine factors
of safety against stem fracture. A kinematic simulation was
derived from the climber's reaction to the log's impact on the
stem to indicate causes for potential harm.
The results are currently being prepared for publication.
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Longitudinal prestresses in
Tilia cordata and Acer pseudoplatanus
Thesis Submitted at the University of Aberdeen
Erk Brudi, Brudi & Partner TreeConsult
Growth stresses occur during cell maturation
and can be considered in a technical sense as prestresses,
increasing the strength of green wood. Prestresses occur in
all three planes causing a tensional longitudinal prestress
and compressive tangential and radial stresses in a tree´s
trunk. In this paper the longitudinal prestress of 10 A. pseudoplatanus
grown in a forest situation at Aberdeen, Scotland and 36 T.
cordata grown as avenue trees in Munich was investigated.
The prestresses measurements were carried out by using the
sawing method and the single hole method for T. cordata (Archer,
1987) and using the single hole method only for A. pseudoplatanus.
The mean E-Modulus for T. cordata was 4947 N/mm² and
for A. pseudoplatanus. 6522 N/mm². The compressive strength
tests carried out with Instron machines were 19,7 N/mm²
for T. cordata and 25,6 N/mm² for A. pseudoplatanus.
The highest increase of prestress was recorded in the first
20 mm drilling/ cutting depth. For T. cordata prestress was
determined with a mean value of 8,3 N/mm² and 3,6 N/mm²
for A. pseudoplatanus. Therefore longitudinal prestresses
increase the breaking safety of T. cordata to 40-50% in average.
In the stiffer A. pseudoplatanus the prestress leads to an
increase of the braking safety of 10-20% only.
See summary
for further details
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