© 2006 Heron Publishing—Victoria, Canada
A finite element model for investigating effects of aerial architecture on tree oscillations
Damien Sellier (1, 2), Thierry Fourcaud (1, 3, 4) and Patrick Lac (1)
1. UMR LRBB, Domaine de l’Hermitage, 69 route d’Arcachon, F-33612 Cestas Cedex, France / 2. UR EPHYSE INRA, B81 F-33883 Villenave d’Ornon Cedex, France / 3. UMR AMAP, CIRAD, TA40/PS2, Boulevard de la Lironde, F-34398 Montpellier Cedex 5, France / 4. Corresponding author (fourcaud@cirad.fr) / Received June 10, 2005; accepted September 30, 2005; published online March 1, 2006
Summary
A finite element model was developed to study the influence of aerial architecture on the structural dynamics of trees. The
model combines a complete description of the axes of the aerial architecture of the plant with numerical techniques suitable
for dynamic nonlinear analyses. Trees were modeled on the basis of morphological measurements that were previously made on
three 4-year-old Pinus pinaster Ait. saplings originating from even-aged stands. Calculated and measured oscillations were compared to evaluate model behavior.
The computations allowed the characteristics of the fundamental mode of vibration to be estimated with satisfactory accuracy.
Inclusion of a topological description of the aerial system in a mechanical model provided insight into the effect of tree
architecture on tree dynamic behavior. Simplifications of the branching pattern in the model led to overestimations of the
natural swaying frequency of saplings by 10 to 20%. Inadequate values of stem and root anchorage stiffness resulted in errors
of 10 to 20%. Modeling results indicated that aerodynamic drag of needles is responsible for 80% of the damping in the studied
trees. Additionally, damping of stem movement is reduced by one half when branch oscillations are not considered. It appears
that the efficiency of the dissipative mechanisms depends directly on crown topology.
Keywords:
damping, dynamics, numerical analysis, oscillation frequencies, tree biomechanics.
