Swaying of Trees as Caused by Wind: Analysis of Field Measurements

1993

41 Lit. Ang.

Unselbständiges Werk

2767

200040916

Measurements of wind and subsequent swaying of two Scots pines (Pinus sylvestris) 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 xycoordinates. 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. These maximum bendings of trees were also in most cases less or equal to those predicted on the basis of static wind loads, when the mean windspeed for static wind load is taken as equal to the gusting windspeed.