|REPORT FOR MEASURING TECHNICAL EXAMINATION OF TREES||2012/1|
Short report on Metrological Trunk and Trunk Base on 02/03/2012 performed as a complement to the visual, mycological and arboricultural assessment.
Baumpflege Team Bodensee
Marcus Pietruschinski, 0179 792 4821
Tel. 07551 / 93 69 99
Fax 07551 / 93 69 89
The beech tree is over 100 years old and recently the fruiting body of a fungus was discovered between the roots. The fungus is a wood-degrading species and therefore an investigation was undertaken to assess the condition of the tree.
Both the acoustic tomography at the foot of the trunk (ARBOTOM) as well as the root diagnosis (ARBORADIX) showed no evidence of a risk of rupture or stability.
Wood identification and depending on a determination of the time of the next follow-up investigation, but not later than 5 years.
The measurement methodology of sound pulse tomography (ARBOTOM ®)
The acoustic tomography method on the trunk is designed to detect and locate possible internal damage or decay. The sensors are usually positioned on the inner and outer radius of maximum deviations (root flares / bumps) or directly to the stem. The first sensor of the measuring chain (usually # 1) is usually in the north direction, unless otherwise stated. The sensors measure the duration of sound pulses (= shock waves) through the wood (in microseconds). From these measurement values, an estimated speed of sound [m / s] is displayed in a coloured line graph. It is an estimate because neither the first nor the exact running track speeds are known. The numerical values of the colour scales correspond to the speed of sound in meters per second [m/s]. An interpretation of the lines and surfaces-tomograms is always possible only in relation to the respective colour scale.
Depending on the species, a computer program calculates a colour face image of the examined section (tomogram). Here, a possible error of principle in the reconstruction of the section of measurement of up to 10 to 30%. To determine more precise figures, measurements in combination with a RESISTOGRAPH is required.
Blue and green areas in the tomogram represent in-tact wood, or where the sound pulse ran quickly and directly. Red or purple areas represent areas of rotten, decayed, damaged or otherwise mechanically decoupled wood.
For tree stability, it is the outer residual wall thickness, well below 1/3 of the radius, or one half of the cross section is damaged, takes its section modulus element against bending sharply, even more, the torsional rigidity decreases. Every tree with lower residual wall thickness is not acutely vulnerable to breakage immediately.
Especially, older trees with reduced crown require lower residual wall thicknesses to be stable and secure.
If necessary, the ARBOTOM® software can be in different colours and number scaling for the running times to be calculated, and various estimated speeds shown: either in terms of an absolute scale (eg 0 .. 2500 m/s) or adjusted to minimum and the maximum of the measured values. On the corresponding tomogram, both scales differ little when the tree in question is intact and there is no damaged wood.
The ‘mechanics-graph’ shows three relative (0 to 100%) scaled curves of the moment of resistance of the cross section to bending by wind from different directions. The green curve is for the intact cross-section, and indicates how the cross-sectional shape of the local mechanical stresses adjusted (eg by wind). The red curve shows the relative resistance torque curve in the light of the tomogram graph and any possibly damaged state.
The blue curve shows the ratio of the green and red curves, so where the blue curve bulges outward most this indicates a weakening of the cross section through the possibly detected damage to the highest percentage reduction of the resistance moment. These considerations are usually used in order to optimise tree care measures if the crown is cut, for example, the most dangerous wind direction as symmetrically as possible, so that there is not yet an additional torsional load occur.
Acoustic pulse imaging for diagnosis root (ARBORADIXTM)
A mechanical pulse is sent into the ground via a steel rod and can find its way to the tree stem if a sufficiently thick (> 2 cm) and woody root is up to about 50 cm below the impact point. If there is no root below where the steel rod was hot (side effect radius 30cm, depending on the terrain), there will be no signal on the tree. The positions of the pulse is introduced into the ground to the root examination are displayed graphically. These measurements are made, depending on the possibility of on-site, usually in intervals of about 1m.
This technique has been applied since 2004 for root analysis and as yet there are no standardised benchmarks. Based on our experience,if a root is severely damaged, decayed or capped, then there is no pulse or (compared to intact roots) very slow pulses to the trunk. The ARBORADIX is a comparative analysis that requires the respective expert to interpret data and there is no numerical determination of stability.
The RESISTOGRAPH ® drills a shaft of 1.5mm thin needle under fast rotation in the wood. Data is recorded and either drawn on a printed readout or stored in memory for later download. Mechanical state depends mainly on the density of the wood at the site of needle tip (3mm). When the drill enters a zone of hard wood (eg: late-wood ring one year) or in a branch, the curve rises; when the drill comes in a soft zone (eg: earlywood ring one year) or a blight, the curve decreases. Although residual wall thicknesses and growth zones can be measured accurately, the RESISTOGRAPH® is only a point measurement. Any significant conclusion on the state of the entire cross-section must be done with caution. Significant inaccuracies can occur without tomographic imaging or further RESISTOGRAPH® measurements.