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Silva Fennica 1926-1997
Acta Forestalia Fennica

Articles containing the keyword 'windspeed'

Category : Article

article id 5505, category Article
Heli Peltola, Jorma Aho, Alpo Hassinen, Seppo Kellomäki, Matti Lemettinen. (1993). Swaying of trees as caused by wind: analysis of field measurements. Silva Fennica vol. 27 no. 2 article id 5505.
Keywords: Pinus sylvestris; wind; windspeed; wind loads; dynamic load; bending
Abstract | View details | Full text in PDF | Author Info

Measurements of wind and subsequent swaying of two Scots pines (Pinus sylvestris L.) were made at stand edge conditions. The horizontal windspeed was measured ten meters outside of the stand edge for four heights using cup anemometers. The compass directions were determined using a directional vane placed above the canopy. Tree swaying was measured by accelerometers at xy-coordinates. The shape of the wind profile at the stand edge varied to some degree depending on windspeed, but the form was a logarithmic one. Swaying of trees increased along with increasing windspeed. Furthermore, swaying was more or less irregular in relation to xy-coordinates, but it occurred, however, mainly perpendicularly to the direction of mean windspeed. The maximum bending of trees to the direction of mean windspeed varied also only little for various gusting windspeeds (average windspeed of 20 seconds) and dynamic wind loads. The maximum bending of trees was also in most cases less or equal to those predicted on the basis of static wind loads, when the mean windspeed for static load is taken as equal to the gusting windspeed.

The PDF includes an abstract in Finnish.

  • Peltola, E-mail: hp@mm.unknown (email)
  • Aho, E-mail: ja@mm.unknown
  • Hassinen, E-mail: ah@mm.unknown
  • Kellomäki, E-mail: sk@mm.unknown
  • Lemettinen, E-mail: ml@mm.unknown
article id 5504, category Article
Heli Peltola, Seppo Kellomäki. (1993). A mechanistic model for calculating windthrow and stem breakage of Scots pines at stand age. Silva Fennica vol. 27 no. 2 article id 5504.
Keywords: Pinus sylvestris; wind; stems; breakage; windspeed; breaking stress; bending models
Abstract | View details | Full text in PDF | Author Info

A model for the mechanism of windfall and stem breakage was constructed for single Scots pine (Pinus sylvestris L.) at the stand edge. The total turning moment arising from the wind drag and from the bending of stem and crown was calculated along with the breaking stress of the stem. Similarly, the support given by the root -soil plate anchorage was calculated. Windspeed variation within the crown and the vertical distribution of stem and crown weight were taken into account. Model computations showed that trees having a large height to diameter ratio were subjected to greater risk of falling down or breaking than trees with a small height to diameter ratio. The windspeed required to blow down a tree or break the stem of a tree decreased if the height to diameter ratio or the crown to stem ratio of trees increased.
The PDF includes an abstract in Finnish.

  • Peltola, E-mail: hp@mm.unknown (email)
  • Kellomäki, E-mail: sk@mm.unknown

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