Dr Ken James
Research Consultant -Trees, stability and winds
Ken James and Associates
Tuesday 9th April | 11:30am
Dynamic concepts of Trees’ Wind Resistance and Mass Damping
Dr Ken James is a research engineer and over 25 years has studied how trees withstand wind storms. Specializing in dynamic loading, his research at Melbourne University reveals that trees are flexible structures and branches sway to provide a damping effect that minimises wind loads.
Dr James has presented at International Arboricultural conferences in Hong Kong, USA, England, Spain, Italy, Holland, Germany, New Zealand, and Australia. He won the L.C. Chadwick Research Award for Arboricultural Research, awarded by the ISA in 2011. Additionally, he has helped develop new instruments to monitor tree stability in winds.
In this presentation, we discuss the dynamic interplay of trees and their branches as they navigate the winds. Dr. James' original research over the last 25 years has significantly advanced our comprehension of how mature urban trees withstand the forces of nature. Trees are flexible structures and the swaying and twisting of branches that collectively form the tree canopy is a complex dynamic system yet to be fully evaluated.
As the winds blow, each branch sways independently, contributing to the overall dynamic motion of the tree. The masses of these branches, in their complex movements, combine and counteract, creating a remarkable dampening effect. This effect minimizes the maximum forces transmitted to the trunk, subsequently reducing the stress on the root plate and soil, ultimately enhancing the tree's survival.
Referred to as "mass damping," this phenomenon is a dynamic force that dissipates energy, effectively reducing maximum loading. It is crucial to note that this damping effect is only present when branches are in motion, absent in still air conditions. This dynamic understanding challenges conventional static assessments used in tree care, urging a shift towards evaluating trees based on their dynamic responses to wind loading.
This presentation navigates the dynamic wind loads experienced by trees, introducing novel concepts such as mass damping that may revolutionize current approaches to tree wind load assessment. Beyond theoretical implications, these dynamic effects may also prompt a re-evaluation of existing pruning practices, particularly those targeting mature urban trees.
Join us on this journey as we unravel the dynamic symphony of trees, reshaping our perspective on their resilience in the face of windstorms.