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BOCA 1999 Snow Drift Loads: Lower RoofsSECTION 1608.0 SNOW LOADS Drift on Lower Roofs 1608.6
25 psf See ASCE 7-98 Section 7.7 ("Leeward Drifts")
Exposure category (Section 1609.4) 2 height between higher and lower roof, h 20 ft
Exposure of Roof (Table 1608.3) 2 277 ft
Building Category (Table 1608.3.3.1) 2 17.3 pcf1.0 ft
See ASCE 7-98 section 7.3 5.3 ft(Eq. 7-1) 5.3 ft
Ce = 1.0 Table 1608.3.1Ct = 1.0 Table 1608.3.2I = 1.0 Table 1608.3.3 Drift Width, W 21.3 ftPf = 17.5 psf 91.7 psf
Engineer: John Smith Date: 4/22/2023Project: Department of Environmental Protection Consolidated Office BuildingLocation: VirginiaContact: Bill JonesCompany: AAA ArchitectsDrift Location: Lower roof
Comments: None
Ground Snow Load (Figure 1608.2), Pg
length of the upper roof, lu
Snow Density, gFlat Roof Snow load (Section 1608.3), Pf height of balanced snow load, hb
calculated drift height, hd(calc)
Pf = 0.7*Ce*Ct*I*Pg drift height, hd
Maximum Drift Snow Load, Pd
lu
Pd+Pf
Pfhhb
hd
W
Wind
BOCA 1999 Snow Drift Loads: Roof ProjectionsSECTION 1608.0 SNOW LOADS Drift on Roof Projections 1608.6.1
30 psf See ASCE 7-98 Section 7.8 ("Windward Drifts")
Exposure category (Section 1609.4) 2 height of roof projection, h 4 ft
Exposure of Roof (Table 1608.3) 2 228 ft
Building Category (Table 1608.3.3.1) 2 17.9 pcf1.2 ft
See ASCE 7-98 section 7.3 3.8 ft(Eq. 7-1) 2.8 ft
Ce = 1.0 Table 1608.3.1Ct = 1.0 Table 1608.3.2I = 1.0 Table 1608.3.3 Drift Width, W 20.8 ftPf = 21.0 psf 50.6 psf
Engineer: John Smith Date: 4/22/2023Project: Department of Environmental Protection Consolidated Office BuildingLocation: VirginiaContact: Bill JonesCompany: AAA ArchitectsDrift Location: Upper Roof: Short Direction
Comments: None
Ground Snow Load (Figure 1608.2), Pg
length of windward roof, lu
Snow Density, gFlat Roof Snow load (Section 1608.3), Pf height of balanced snow load, hb
calculated drift height, hd(calc)
Pf = 0.7*Ce*Ct*I*Pg drift height, hd
Maximum Drift Snow Load, Pd
lu
Pd+Pf
Pfhhb
hd
W
Wind
IBC 2000 Snow Drift Loads: Lower RoofsSECTION 1608 SNOW LOADS Drift on Lower Roofs 1608.7
44.6 psf See ASCE 7-98 Section 7.7 ("Leeward Drifts")
Terrain category (Section 1609.4) 2 height between higher and lower roof, h 8 ft
Exposure of Roof (Table 1608.3.1) 2 275 ft
Building Category (Table 1604.5) 4 19.8 pcf1.3 ft
See ASCE 7-98 section 7.3 6.1 ft(Eq. 7-1) 6.1 ft
Ce = 1.0 Table 1608.3.1Ct = 1.0 Table 1608.3.2
0.8 Table 1604.5 Drift Width, W 24.4 ftPf = 25.0 psf 120.8 psf
Engineer: John Smith Date: 4/22/2023Project: Department of Environmental Protection Consolidated Office BuildingLocation: VirginiaContact: Bill JonesCompany: AAA ArchitectsDrift Location: Lower roof:west side
Comments: None
Ground Snow Load (Figure 1608.2), Pg
length of the upper roof, lu
Snow Density, gFlat Roof Snow load (Section 1608.3), Pf height of balanced snow load, hb
calculated drift height, hd(calc)
Pf = 0.7*Ce*Ct*I*Pg drift height, hd
Is =
Maximum Drift Snow Load, Pd
lu
Pd+Pf
Pfhhb
hd
W
Wind
IBC 2000 Snow Drift Loads: Roof ProjectionsSECTION 1608 SNOW LOADS Drift on Roof Projections 1608.8
44.6 psf See ASCE 7-98 Section 7.8 ("Windward Drifts")
Terrain category (Section 1609.4) 2 height of roof projection, h 5 ft
Exposure of Roof (Table 1608.3.1) 2 300 ft
Building Category (Table 1604.5) 4 19.8 pcf1.3 ft
See ASCE 7-98 section 7.3 4.7 ft(Eq. 7-1) 3.7 ft
Ce = 1.0 Table 1608.3.1Ct = 1.0 Table 1608.3.2I = 0.8 Table 1604.5 Drift Width, W 24.1 ftPf = 25.0 psf 74.0 psf
Engineer: John Smith Date: 4/22/2023Project: Department of Environmental Protection Consolidated Office BuildingLocation: VirginiaContact: Bill JonesCompany: AAA ArchitectsDrift Location: Lower roof:west side
Comments: None
Ground Snow Load (Figure 1608.2), Pg
length of windward roof, lu
Snow Density, gFlat Roof Snow load (Section 1608.3), Pf height of balanced snow load, hb
calculated drift height, hd(calc)
Pf = 0.7*Ce*Ct*I*Pg drift height, hd
Maximum Drift Snow Load, Pd
lu
Pd+Pf
Pfhhb
hd
W
Wind
ASCE 7-98 Snow Drift Loads: Lower Roofs7.0 SNOW LOADS 7.7 Drifts on Lower Roofs
25 psf "Leeward Drifts"
Terrain category (Section 6.5.6) 2 height between higher and lower roof, h 8 ft
Exposure of Roof (Table 7-2) 2 275 ft
Building Category (Table 1-1) 4 17.3 pcf1.2 ft5.3 ft
(Eq. 7-1) 5.3 ft
Ce = 1.0 Table 7-2Ct = 1.0 Table 7-3
1.2 Table 7-4 Drift Width, W 21.2 ftPf = 21.0 psf 91.4 psf
Engineer: John Smith Date: 4/22/2023Project: Department of Environmental Protection Consolidated Office BuildingLocation: VirginiaContact: Bill JonesCompany: AAA ArchitectsDrift Location: Lower roof:west side
Comments: None
Ground Snow Load (Figure 7-1), Pg
length of the upper roof, lu
Snow Density, gFlat Roof Snow load (Section 7.3), Pf height of balanced snow load, hb
calculated drift height, hd(calc)
Pf = 0.7*Ce*Ct*I*Pg drift height, hd
Is =
Maximum Drift Snow Load, Pd
lu
Pd+Pf
Pfhhb
hd
W
Wind
ASCE 7-98 Snow Drift Loads: Roof Projections7.0 SNOW LOADS 7.8 Roof Projections
25 psf "Windward Drifts"
Terrain category (Section 6.5.6) 2 height of roof projection, h 6 ft
Exposure of Roof (Table 7-2) 2 277 ft
Building Category (Table 1-1) 1 17.3 pcf0.8 ft4.0 ft
(Eq. 7-1) 4.0 ft
Ce = 1.0 Table 7-2Ct = 1.0 Table 7-3I = 0.8 Table 7-4 Drift Width, W 16.0 ftPf = 14.0 psf 68.8 psf
Engineer: John Smith Date: 4/22/2023Project: Department of Environmental Protection Consolidated Office BuildingLocation: VirginiaContact: Bill JonesCompany: AAA ArchitectsDrift Location: Lower roof:west side
Comments: None
Ground Snow Load (Figure 7-1), Pg
length of windward roof, lu
Snow Density, gFlat Roof Snow load (Section 7.3), Pf height of balanced snow load, hb
calculated drift height, hd(calc)
Pf = 0.7*Ce*Ct*I*Pg drift height, hd
Maximum Drift Snow Load, Pd
lu
Pd+Pf
Pfhhb
hd
W
Wind
BOCAExposure category Table 1608.3.1
1 A2 B Fully Partially Sheltered3 C Exposure Category 1 2 34 D A 1 NA 1.1 1.35 Special B 2 0.9 1 1.2
C 3 0.9 1 1.1Exposure of Roof D 4 0.8 0.9 1
1 Fully Exposed Special 5 0.7 0.8 NA2 Partially Exposed3 Sheltered
Table 1608.3.3Building Category 2
1 I I 1 0.82 II II 2 13 III III 3 1.14 IV IV 4 1.2
IBCTerrain category Table 1608.3.1
1 A2 B Fully Partially Sheltered3 C Exposure Category 1 2 34 D A 1 NA 1.1 1.35 Special B 2 0.9 1 1.2
C 3 0.9 1 1.1Exposure of Roof D 4 0.8 0.9 1
1 Fully Exposed Special 5 0.7 0.8 NA2 Partially Exposed3 Sheltered
Table 1608.3.3Building Category
1 I I 1 12 II II 2 1.13 III III 3 1.24 IV IV 4 0.8
ASCE 7Terrain category Table 1608.3.1
1 A2 B Fully Partially Sheltered3 C Exposure Category 1 2 34 D A 1 NA 1.1 1.35 Special B 2 0.9 1 1.2
C 3 0.9 1 1.1Exposure of Roof D 4 0.8 0.9 1
1 Fully Exposed Special 5 0.7 0.8 NA2 Partially Exposed3 Sheltered
Table 1608.3.3Building Category
1 I I 1 0.82 II II 2 13 III III 3 1.14 IV IV 4 1.2
