Snow-creep forces on masts

Abstract

Since 1975, the Norwegian Geotechnical Institute has performed field investigations of snow-creep forces on masts at the research site in Grasdalen, Stryn mountains in Norway. Two poles, with diameters of 419 and 219 mm, respectively, were erected at the site together with a retaining structure. On both poles, strain gauges were mounted in pairs every 0.5 m to find the axial stresses and the moments in different sections. In the middle section of the retaining structure, the beams and supporters were instrumented to obtain measurements of the strains and stresses. Snow glide was controlled by glide shoes mounted at the rock surface above the structures.During the winter, snow profiles were made systematically; these included measurements of snow depth, density and temperature, and observations of snow type and moisture content. By relating the measured stresses and moments in the structures to the snow depth, it was possible to find the snow-pressure distribution. A comparison of the snow pressures with the “Body force index” (product of snow depthh,densityρand acceleration due to gravityg), show a close relationship for the wall element. For the pole elements, the snow temperature during the winter is an added factor of high importance and the highest pressures on these elements occur in winters with long periods of 0°C isothermal snowpack.

Snow forces on forest plants due to creep and glide

“…Larsen's (1998) measurements show very small glide rates (which seems to be different from conditions in the Alps); therefore his equation does not include a parameter for snow gliding.…”

“…However, to consider the end-effect forces on small obstacles it is necessary, as stated above, to include a correction factor. Larsen (1998) Larsen (1998) has measured snow pressure on two masts at a research site in Grasdalen (Norway) and formulated an equation to calculate the pressure q [N m À1 ] on obstacles with different diameters:…”

“…The method from Larsen (1998) was not taken into account. The reason is that the equation was designed for conditions in Norway and does not specifically consider the situation in the Alps.…”