Wind Load on Saudi Arabia according to U B C 1997 Design Wind Pressure in psf (P) P = Ce Cq qs Iw a. qs Wind stagnation pressure in psf at height of 33' (10 meter) above the ground . qs = 0.00256 V2 Where V = Wind speed in mph
Basic Wind Speed Pressure qs
mph mps psf kg/m2
70 31 12.6 61.5
80 36 16.4 80.1
90 40 20.8 101.6
100 45 25.6 125.0
110 49 31 151.4
120 54 36.9 180.2
130 58 43.3 211.4
By / Eng Khalid Omar Hanafy
[email protected]
b. Iw Importance factor x Essential facilities and hazardous facilities are designed to withstand higher forces by setting Iw = 1.15, which is approximately equivalent to a 100 year recurrence interval. x Otherwise, Iw = 1.0
C. Ce Combined height, exposure, gust coefficient Wind pressure increases with building height: x For the Windward wall , UBC uses stepped pressure diagram x For leeward wall, pressure taken as constant over the full wall height and is calculated using the mean roof height for CE determination.
Height Above Average Level of Adjoining Ground feet
meters
0 - 15 20 25 30 40 60 80 100 120 160 200 300 400
0 - 4.6 6.1 7.6 9.1 12.2 18.3 24.4 30.5 36.6 48.8 61.0 91.4 121.9
Exposure D
Exposure C
Exposure B
1.39 1.45 1.5 1.54 1.62 1.73 1.81 1.88 1.93 2.02 2.1 2.23 2.34
1.06 1.13 1.19 1.23 1.31 1.43 1.53 1.61 1.67 1.79 1.87 2.05 2.19
0.62 0.67 0.72 0.76 0.84 0.95 1.04 1.13 1.2 1.31 1.42 1.63 1.8
B - Urban, suburban, closely spaced obstruction the size of single - family residences. C - Open country and grasslands that are generally flat. D - Unobstructed flat terrain facing a large body of water extending inland 1/4 mile or ten times building height, whichever is greater.
By / Eng Khalid Omar Hanafy
[email protected]
C. Cq Pressure Coefficient Description Walls
Roofs
Cq Factor
Windward wall
0.8 inward
Leeward wall
0.5 outward
Wind perpendicular to ridge Leeward roof or flat roof
0.7 outward
Windward roof
0.7 outward
less than 2:12 (16.7%)
0.9 outward or 0.3 inward
Slope 2:12 (16.7%) to less than 9:12 (75%)
0.4 inward
Slope 9:12 (75%) to 12:12 (100%)
0.7 inward
Slope > 12:12 (100%)
0.7 outward
Using Etabs 2000,SAP 2000 to generate Wind load
Define > Static load Cases
Add wind case and select UBC 97 then click modify lateral load Select to manually add wind Coefficient (Cq) on shell and dummy element Height of wind affection Wind speed in jeddah Wind speed in jeddah B for urban . Importance factor
By / Eng Khalid Omar Hanafy
[email protected]
