Item: How reliable are design avalanche loads? A systematic approach to estimate their uncertainty
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Title: How reliable are design avalanche loads? A systematic approach to estimate their uncertainty
Proceedings: International Snow Science Workshop Proceedings 2018, Innsbruck, Austria
Authors:
- Mark Schaer [ WSL Institute for Snow and Avalanche Research SLF, 7260 Davos Dorf, Switzerland ]
- Katharina Fischer [ Matrisk GmbH, 8910 Affoltern am Albis, Switzerland ]
- Stefan Margreth [ WSL Institute for Snow and Avalanche Research SLF, 7260 Davos Dorf, Switzerland ]
Date: 2018-10-07
Abstract: The assessment of avalanche loads depends partly on well-founded facts such as observed avalanches, but the avalanche expert generally also has to make many assumptions that are difficult to base on objective evidence. This is particularly true for avalanche tracks with complex release zones and for the assessment of avalanches with a long return period, where little empirical data is available. However, an engineer requires precise load values for example for the design of a snow shed. We present a study where we analysed a well documented avalanche track in Davos that has a snow shed at the bottom. To estimate the uncertainty of the avalanche loads on the snow shed, we varied the decisive input parameters to perform numerical avalanche simulations systematically and asked three experts to estimate the probability of each parameter value. Several thousand avalanche-dynamic simulations with the software RAMMS were performed to cover all possible parameter combinations and the avalanche load on the snow shed was computed for each run. Using the probabilities that were estimated for the input parameters, we calculated the probability distribution for the avalanche load and the probability for the load exceeding the bearing capacity of the structural system of the snow shed. The main conclusions are: (a) Although the involved experts have all a long experience and a similar professional background, their estimations varied by a factor of 2.8 for the maximum load related to a 300-year return period. (b) For the snow shed, we got a failure probability in the order of 1E-3 per winter. This number is compatible with the low number of documented snow shed collapses, but below the requirements of European building codes which require an annual failure probability of 1E-5 or lower, depending on the consequence class.
Language of Article: English
Presenters:
Keywords: avalanche loads, avalanche dynamic simulations, snow shed, probabilistic approach, failure probability, building codes.
Page Number(s): 181-185
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Digital Abstract Not Available
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