A method for measuring the forces acting on a tree trunk using strain gauges

Area of Science:

• Arboriculture
• Biomechanical Engineering
• Environmental Science

Background:

• Wind exerts dynamic forces on trees, influencing their stability and growth.
• Accurate measurement of wind force magnitude, distribution, and direction is crucial for ecological and structural studies.

Purpose of the Study:

• To develop and validate a method for simultaneously measuring wind force (F), centroid (C), and direction (D) on tree trunks.
• To overcome challenges of sensor alignment and material irregularities in field measurements.

Main Methods:

• Utilized four strain gauges attached to the tree trunk.
• Estimated force (F) and centroid (C) from bending moments at two stem positions.
• Estimated force direction (D) using sensor outputs at different radial positions.
• Developed a novel calibration method to determine strain gauge position and elasticity after attachment.

Main Results:

• Achieved estimation errors of less than 2% for both distributed and circumferential tensile loads.
• Demonstrated precise estimation of F, C, and D even with uneven wood surfaces and non-ideal strain gauge alignment.
• Validated the method on wood poles and conifer saplings under various loading conditions.

Conclusions:

• The developed method provides accurate and reliable field measurements of wind forces on trees.
• This technique is advantageous for ecological research, forestry, and structural assessments of trees under wind loads.