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Rowville, Australia

James K.R.,ENSPEC Pty Ltd | Dahle G.A.,West Virginia University | Grabosky J.,Rutgers University | Kane B.,University of Massachusetts Amherst | Detter A.,Brudi and Partner
Arboriculture and Urban Forestry | Year: 2014

Tree biomechanics studies using dynamic methods of analysis are reviewed. The emphasis in this review is on the biomechanics of open-grown trees typically found in urban areas, rather than trees in forests or plantations. The distinction is not based on species but on their form, because open-grown trees usually grow with considerable branch mass and the dynamic response in winds may be different to other tree forms. Methods of dynamic analysis applied to trees are reviewed. Simple tree models have been developed to understand tree dynamic responses, but these largely ignore the dynamics of branches. More complex models and finite element analyses are developing a multimodal approach to represent the dynamics of branches on trees. Results indicate that material properties play only a limited role in tree dynamics and it is the form and morphology of the tree and branches that can influence the dynamics of trees. © 2014 International Society of Arboriculture. Source


Kane B.,University of Massachusetts Amherst | Modarres-Sadeghi Y.,University of Massachusetts Amherst | James K.R.,ENSPEC Pty Ltd | Reiland M.,University of Massachusetts Amherst
Trees - Structure and Function | Year: 2014

Key message: Our manuscript provides novel information about the sway response of large, open-grown trees, for which there are very few data. Our results contrast previous studies on conifers. Open-grown trees in residential settings, which often assume a decurrent form, provide many benefits but also pose a risk to people and property if they fail. Reliable mechanistic models to predict failure of such trees are uncommon. Parameters to describe dynamic oscillations such as natural frequency (f n) and damping ratio (ζ) are important components of mechanistic models, but few data exist for large, open-grown trees. Attributes of crown architecture and tree size as well as f n and ζ were measured on eight large, open-grown sugar maples (Acer saccharum) growing in Belchertown, MA, USA. Although previous work has not demonstrated this correlation, f n was directly proportional to the cumulative diameter of primary branches. Similarly, previous work has not established reliable predictive models for ζ, which was directly proportional to crown width of sugar maples. Predicting f n from the cumulative diameter of primary branches is consistent with the multi-modal dynamic response of trees. Predicting ζ from crown width appeared to be due to aerodynamic damping, consistent with previous studies on broad-leaf trees. © 2013 Springer-Verlag Berlin Heidelberg. Source


James K.R.,ENSPEC Pty Ltd | Hallam C.,ENSPEC Pty Ltd
Arboricultural Journal | Year: 2013

The stability of trees in storms and high winds was assessed with newly developed tilt instruments that measure the structural properties of tree root plates and their anchorage strength in the ground. Tree root plates flex slightly in the ground when strong winds blow and the tilt instruments measure this flexure continuously. Tilt accuracy of 0.01° was measured at 20 samples per second, which is sufficient to record the dynamic response of the tree in high winds. The instrument has battery power for up to 20 days recording and is simply connected to a computer via a USB cable. Five Norfolk Island pines (Araucaria heterophylla) at Burnie, Tasmania were monitored during a period of high winds. Each tree had one tilt sensor attached to the trunk at ground level and another approximately 3 m above the ground. Tilt data during high winds for the five trees are presented. Tree 5 recorded maximum tilt of 0.40°, which was higher than nearby trees (0.10-0.15°) but is still within acceptable limits that are considered stable. The results indicate that Tree 5 has re-established a root system after previous construction damage and has now stabilised. It is planned to remove the supporting cables and use the tilt sensors annually to monitor the stability of trees. © 2013 Taylor & Francis and Aboricultural Association. Source


James K.,ENSPEC Pty Ltd | Hallam C.,ENSPEC Pty Ltd | Spencer C.,ENSPEC Pty Ltd
Biosystems Engineering | Year: 2013

Tree stability in winds was evaluated by measuring the tilt of the root plate using newly developed instruments that attached to the trunk at ground level. During periods of high winds, tilt sensors recorded data on the dynamic flexure of a tree's root plate which was used to assess the anchorage strength of the tree in the ground. The root plate tilt of 250 trees at 30 sites in Victoria, Australia was measured under natural wind conditions from November 2010 to August 2012. The maximum root plate tilt values recorded were 0.90° on an Eucalyptus obliqua and 0.88° on an Eucalyptus rubida. These data were recorded during strong winds on 11 June 2011 for E. rubida and on 5 September 2012 for both trees. The majority of trees (96%) recorded tilt values below 0.50°, even in high winds. No trees failed during this study and 11 trees (4%) recorded maximum tilt values above 0.50°. Static pull tests on 10 trees were conducted to determine root plate tilt under controlled loading and to obtain tilt values for comparison to wind induced tilt data. Tilt data of tree root plates in winds is discussed in relation to anchorage strength in the ground and tree stability. No trees in this study failed even though several strong winds occurred during which tree failures were reported in nearby localities. Further work is needed to measure tilt values during tree failure in wind, in order to establish the limits of tilt that will define tree stability. © 2013 IAgrE. Source

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