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Show Bending moment M = P h2u/ 2 = 1900 kg- m Stress cr = M/ W = 240 kg/ cm2 ( VII): Run out distance s = 380 m Local observations [ ll]; Although the telephone poles standing in the avalanche path remained intact for the most part ( the breaking stress of about 400 kg/ cm2 was not reached,) debris from the destroyed structures was carried as much as 350 m onto the valley plain. b) Break of the suspension tower on the 50 kv transmission line between Davos and Filizur in January 1951 [ l5]. Constructed according to plans MC ( 9706/ 82); tower height 19 m. Angle between the avalanche's direction of action and the transmission cable Ys ~ 30°. Natural new snow height h = 1 m; y0 = 200 kg/ m3. Release zone gradient 30%; gradient in the zone of destruction 20%. Eq. ( Ill, b): Yu = 6 kg/ m3, hu = 33 m ( III ): v = 56.5 m/ sec The snow pressure of the powder avalanche acted upon the entire tower height. Thrust on the four steel tubes of 10 cm diameter, taking into consideration the velocity distribution according to Equation ( IV): P = 4(- d/ 4) ( Y v2/ 2g) = 300 kg/ m Moment from the snow pressure M = 50,000 kg- m Moment in the longitudinal direction of the avalanche M . cosP = 44,000 kg- m Verification from the construction: The tower constructed with a factor of safety of about 2.5 for normal stresses, showed a mathematical breaking moment of about 20,000 kg- m, referred to the mast footings. The breaking load was exceeded by the thrust of the avalanche by about a factor of two. c) Avalanche accident at Zuoz 1951 [ l5] h = 1.23 m; Y 0 = 282 kg/ m3, + m = 24<> In the release zone • 0 = 29°, at the valley floor ty u = 10° ascending ( average value) Mixed surface and powder avalanche: Eq. ( Ill, 10) ( III, 9) ( V ) Y = 15 kg/ m3 h* = 23 m hu= 24.5 m 53 |
