Evaluation algorithm improvement in the DynaRoot / DynaTree software
Due to recent findings, we decided to implement a stricter evaluation procedure.
The new algorithm only takes the measurement points that are exhibiting the highest inclination (as indicated in the image above). For this reason, the function fitted to the data will match the critical, high inclination points better. This will result in a lower safety factor (SF).
In the past we have verified DynaRoot / DynaTree measurements by comparing them to Pulling Test results. This showed a good correlation and gave us confidence in the system. We have also received feedback confirming this correlation from our users. However seeing the recent uprooting, we are forced to implement changes to the algorithm.
Please note that the previously measured safety factors will become around 40% lower than before with the new algorithm. We understand that it is a serious change but we need to stand on the side of safety. Thank you for your understanding.
Wind direction dependency in Dynamic root testing
The encircled Eucalyptus sp. tree was tested over several days at high wind velocity during February 2022 with DynaRoot dynamic root testing system. The tree is approximately 17 meters tall and has a diamater of 44 cm at breast height. The measurements were conducted in the United Kingdoms by Mr. James Chambers, Tim Moya Asssociates.
Eucalyptus sp.
Inclinometer
Anemometer
Location
The image on the left shows the satellite image of the surrounding area of the measured tree. The red cross indicates the tree in question, while the yellow cross indicates the location of the wind anemometer. It is clearly visible that the tree is protected from the wind from the south, southwest and southeast by several large buildings, while completely exposed to the wind in any other direction.
Measurements
Date
max. wind speed (km/h)
wind direction (degree)
Safety Factor
correlation
Oct. 27
84
340
0.94
0.95
Feb. 18/1
113
208
3.96
0.94
Feb. 18/2
119
260
0.96
0.95
Feb. 18/3
53
243
1.24
0.72
Feb. 19/1
72
259
1.1
0.82
Feb. 19/2
68
221
2.89
0.76
Feb. 20
72
215
2.89
0.72
Feb. 20/1
94
281
0.92
0.85
Feb. 20/2
50
307
0.84
0.68
The table above shows the measured speed and the direction of the wind, with the corresponding Safety Factor calculated by the software. The results show that from protected directions (S,SW,SE) the Safety Factor is significantly higher. From unprotected directions (West ~ 260°, NW ~ 340°) the Safety Factor is below 1 which is deemed unsafe by the software. On the right the arrows indicate some of the wind directions.
The graph shows that after the change in wind direction (red line) the inclination measured on the tree became significantly higher.
Conclusions
Ultimately as the gathered data shows, the results of DynaRoot is highly influenced by wind direction. It is extremely important to always take the wind direction into consideration when evaluating DynaTree measurements. When a high Safety Factor is due to the tree being shielded from the wind (by other trees, buildings), it is recommended to repeat the measurement in unobstructed wind.
Pulling test: The effect of cut roots on safety factor
A brief case study by Tibor Horvath with Fakopp Pulling Test
Conditions
The measured tree stood in a suburban garden and has been marked for removal.
The removal has been turned into a series of 6 pulling tests. First we measured the tree in its original state, then before every additional pulling test some of roots have been cut.
For the calculation of the safety factors, the wind speed of 33 m/s (cc. 120 km/h) has been used.
The purpose of the experiment was to reveal the effect of cut roots on the safety factor.
Safety factor measurements
Intact: 1.19
Excavated: 0.86
1 root cut: 0.61
4 roots: 0.33
7 roots: 0.27
All 11 roots: 0.14
Results
Ludwig sensor test of a Platanus occidentalis
A Platanus occidentalis tree has been selected for examination in a botanical garden (Sopron, Hungary). First the measurement has been conducted with 12 regular sensors and then with an additional 12 Ludwig sensors.
The first measurement using 12 regular sensors shows a decayed area in the middle (about 40%).
The second measurement with additional Ludwig sensors shows a decayed area in the middle (about 32%), and also a strengthened area on the side near sensors 9-12.
The tree suffered a freeze injury several years ago. This is exactly the part where the strengthened wood has been found.
