Snow Loading On Snow Loading On The Territory Of The Territory Of BulgariaBulgaria

E. Moraliiski, Cv. Dimitrov

BackBack--ground of the ground of the ProblemProblem

ENV 1991 – NLIBTE (01.07.1989)196450 years (EUROCOD 1)Determined indirectly:

m=h.ρ

50 stations1000 – 1200 m

BackBack--ground of the ground of the ProblemProblem

Basic problem of in climatic ensuring -to suffer minimum losses

Concrete caseType of building and its functionPeriod of exploitationFulfill the building standard

Probable characteristics (SL)Package of maps

1:5 ; 1:10 ; 1:20 ; 1:25 ; 1:50 years

Annual Maximum of Annual Maximum of Snow Cover DepthSnow Cover Depth

Territory of country (Area - occur):A (1000-1200): January – February

Varna 76%Obraztzov Chiflik 69%Sofia 60%

B (mountain regions): March – AprilPeak Cherny Vrah 50% - 3

Individual method of approach (SL)

Average annual maximum Average annual maximum depth of snow cover (cm)depth of snow cover (cm)

Station 1931-1970 1971-2000Vidin 37 30

Gabrovo 41 43Veliko

Tarnovo 39 31

Ruse 32 32Varna 14 9Burgas 17 10Plovdiv 22 22

Kustendil 40 27

Annual Maximum of Annual Maximum of Snow Cover DepthSnow Cover Depth

Individual method of approach (SL)Data

193 stations1961 – 2000 (map)

Period (h, P%)30 years (1971 - 2000)

Approximation II type Fisher-Tippet:

( )ϕβ

h x e x a≤ = − −( / )

Annual Maximum of Annual Maximum of Snow Cover DepthSnow Cover Depth

Values of maximum snow cover depth are calculated by

T – number of years (period)X - depth of snow cover

MSCD values that likely to occur (5,10,25,50)integral distribution curve

( )ϕ xT

= −⎛⎝⎜

⎞⎠⎟

⋅1 1 100

The Annual Maximum of Snow Cover The Annual Maximum of Snow Cover Depth (cm) with different integral Depth (cm) with different integral probability, (1)probability, (1)--1931/70, (2)1931/70, (2)-- 71/200071/2000

Station Period 1:5 1:10 1:25 1:50

1 69 90 130 170Gabrovo 2 55 68 90 1101 45 57 76 95Veliko

Tarnovo 2 45 56 76 951 43 60 95 132Ruse 2 45 61 90 1181 25 38 64 97Varna 2 14 19 28 371 28 42 71 105Burgas 2 19 28 5 651 26 33 47 58Plovdiv 2 20 27 35 42

The Density of Snow The Density of Snow CoverCover

0

50

100

150

200

250

300

0 0.1 0.2 0.3 0.4 0.5 0.6

r, gr/cm3

h, c

m

Dependence on (altitude, h)50 stationsArea A (1000,1200) constant density210 kg/m3

Area B max(3,4) the dependence is taken into account (fig)Maximum values in B area during spring can exceed 600 kg/m3

The Density of Snow The Density of Snow CoverCover

ASD – appendix E of PREN 1991-1-3, dependence on snow type – driven snow, old (compact) snow and slush (1-4) KN/m2

Area B (3,4) measured 2 m, up to 4.5 KN/m2

Water content – duration SL with respective intensity

Continued snow loadingof short duration snow loading

Areas with enormous SL (map)

The snow cover Depth h (The snow cover Depth h (cmcm) ) and density rand density r (g/cm(g/cm33))

Month X XI XII I II III IV

PetrohanAv. 18 0.14 19 0.17 28 0.21 44 0.25 58 0.28 63 0.31 34 0.30Max. 29 0.28 75 0.39 74 0.61 162 0.51 182 0.48 178 0.67 100 0.55

BorovetzAv. 14 0.20 20 0.16 17 0.20 29 0.19 35 0.22 35 0.26 26 0.25Max. 16 0.22 53 0.47 48 0.40 76 0.36 100 0.46 71 0.53 93 0.62

Peak Cherny VrahAv. 38 0.30 74 0.33 95 0.36 127 0.37 150 0.40 130 0.44Max. 90 0.46 82 0.59 170 0.53 233 0.50 223 0.54 260 0.60

The Density of Snow The Density of Snow CoverCover

Recommended by EUROCOD 1:Specify (2, 50 years, extraordinary situation)

Bulgaria (h>1200m)

Specify areas with enormous snow-blowingBulgaria (NE, mountain areas)

ISO/FDIS 4355 – coefficient of exposure (V,T)prEN 1991-1-3 (map - GIS)

Reduced to sea level values (Italy, Denmark, etc)Actually values (Norway, Poland, etc)

The Density of Snow The Density of Snow CoverCover

Characteristic value SL (DN, altitude):Nonlinear dependence (most country)Linear (Switzerland, France, etc)In Bulgaria – dependence has importance for B area

Dividing into district – free choice of gradation –standardizeEUROCOD 1 – rain before snow be melted completely SL↑Bulgarian’s Bleak sea cost – different district (0)Acceptance of EUROCOD 1 → Bulgaria (SL↑, 2 – 4 times)

In BG – 2005 was accepted SL (1:25)

Average maximum annual Average maximum annual mass of snow covermass of snow cover

Station Snow Mass (kg/m2)Vidin 65.0

Pleven 65.9Shumen 64.5Varna 21.8Burgas 35.9Sadovo 53.1Sofia 49.6

Blagoevgrad 34.9

Dividing of Bulgaria’s Dividing of Bulgaria’s Territory Into Snow Territory Into Snow Loading DistrictsLoading Districts

Dividing of the territory on SL districts:Area A (1000-1200 m)Area B: small number of stations, ρ(h,altitude)Drawing the iso-lines over sides of a mountains:

Local gradient (respective mountain, slope exposure)No data – G gradient (exposure of the mountain slope)

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