Defense structures in avalanche starting zones - SLF

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$N e w s l e t t e r N a t u r g e f a h r e n Schneeverfrachtung - SLF$

Technical Guideline for Defense Structures in Avalanche Starting Zones FOEN / WSL 2007 48 4.5 End-effect loads With finite width of the supporting surface in the contour line, incremental end-effect loads occur by virtue of the fact that the snow can flow laterally around the surface, so that a lateral restraining effect occurs. The end-effect loads are dependent not only on the factors determining the snow pressure on an infinitely wide surface, but also on the dimensions, shape and surface roughness of the grate, and even more so on the glide factor. The basic snow pressure distribution is shown in Fig. 17. For practical calculations, the end-effect force is substituted by an equivalent, constant, force per meter run S'R acting over the length Δl (see Section 5.5.2.4). The influence factor η relating to the pressure transfer to a supporting structure or a slender element can be defined as the ratio of the effective snow pressure including end-effect loads to the snow pressure excluding end-effect loads. Fig. 17 > Snow pressure distribution on a supporting surface of finite width. Assumption for calculation Actual distribution
4 > Overview of snow pressure effects 49 4.6 Snow pressure on slender elements of a supporting structure 4.6.1 Snow pressure on supports The supports of rigid supporting structures and snow nets are subject to downslope forces due to snow masses attached to the underside of the structure (Fig. 18). The magnitude of the transverse load is strongly dependent on the influence factor η of the support. With heavy snow glide, the influence factor increases. The snow pressure on the supports can be assumed as a uniformly distributed line load q'S: support diameter = η ⋅ S' ⋅ ⋅ sin α [kN/m'] (15) support length q'S N q's snow pressure on support represented by a line load. The direction of q's is normal to the axis of the support. The load impinges along the axis of the support [kN/m']. η influence factor of the support. S'N snow pressure component in the line of slope per meter run of the supporting surface [kN/m'], equation (11). - diameter and length of support [m]. α Angle between the support axis and the surface of the ground [°]. Fig. 18 > Snow pressure q'S on the support of a snow net. Swivel support q' q' q'SS S Length Length Length of of of support support support α S' S' S'NN N Net Diameter of support
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Defense structures in avalanche starting zones - SLF

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