In order for a structure to be sound and secure, the foundation, roof, and walls must be strong and wind resistant. When building a structure it is important to calculate wind load to ensure that the structure can withstand high winds, especially if the building is located in an area known for inclement weather. The main wind force resisting system of a building is a vital component. While wind load calculations can be difficult to figure out because the wind is unpredictable, some standard calculations can give you a good idea of what a building can withstand. Wind loading analysis is an essential part of the building process. If wind loading analysis is not done correctly the resulting effects could include collapsed windows and doors, ripped off roofing, and more. Contact BuildingsGuide for quotes on safe and durable prefabricated steel buildings.
Types of Wind Load Forces on Buildings:
- Shear Load – Wind pressure that is horizontal and could make a building tilt.
- Lateral Load – A pulling and pushing horizontal pressure that can cause a building to move off its foundation.
- Uplift Load – Pressures from wind flow that cause lifting effects.
To assist in your wind loading analysis, use the following wind load calc to get the necessary wind load calculations. Accurate wind load calculations will that a safe, durable structure is assembled.
Wind Loading Analysis - Main Wind-Force Resisting System, per ASCE 7-05 Code [wind loads on structures 2005] for Enclosed or Partially Enclosed Buildings
Using Method 2: Analytical Procedure (Section 6.5) for Low-Rise Buildings
|Wind Speed, V =||mph (Wind Map, Figure 6-1)|
|Bldg. Classification =||[?]||(Table 1-1 Occupancy Cat.)|
|Exposure Category =||(Sect. 6.5.6)|
|Ridge Height, hr =||ft. (hr >= he)|
|Eave Height, he =||ft. (he <= hr)|
|Building Width =||ft. (Normal to Building Ridge)|
|Building Length =||ft. (Parallel to Building Ridge)|
|Roof Type =||(Gable or Monoslope)|
|Topo. Factor, Kzt =||(Sect. 6.5.7 & Figure 6-4)|
|Direct. Factor, Kd =||(Table 6-4)|
|Enclosed? (Y/N)||(Sect. 6.2 & Figure 6-5)|
Resulting Parameters and Coefficients:
Occupancy Category of Buildings and Other Structures for Flood, Wind, Snow, Earthquake, and Ice Loads
Nature of Occupancy
|Buildings and structures that represent a low hazard to human life in the event of failure including, but not limited to:
- Agriculture facilities
|Buildings and other structures except those listed in Categories I, III and IV||II|
| Buildings and other structures that represent a substantial hazard to human life in the event of failure including, but not limited to:
- Buildings and other structures where more than 300 people congregate in one areaBuildings and other structures, not includes in Occupancy Category IV, with potential to cause substantial economic impact and/or mass disruption of day-to-day civilian life in event of failure, including, but not limited to:
- Power generating stations, water treatment facilities, sewage treatment facilities, and telecommunication centers
| Buildings and other structures designated as essential facilities including, but not limited to:
- Hospitals and health care facilities having surgery or emergency treatment facilities
Surface Roughness Categories for the purpose of assigning Exposure Category are defined as follows:
Surface Roughness "B":
Urban and suburban areas, wooded areas or other terrain with numerous closely spaced obstructions having the size of single family dwellings or larger.
Surface Roughness "C":
Open terrain with scattered obstructions having heights generally < 30 ft. This category includes flat open country, grass lands, and all water surfaces in hurricane prone regions.
Surface Roughness "D":
Flat, unobstructed areas and water surfaces outside hurricane prone regions. This category includes smooth mud flats, salt flats, and unbroken ice.
Exposure Categories are defined as follows:
Exposure B shall apply where the ground surface roughness condition, as defined by Surface Roughness B, prevails in the upwind direction for a distance of at least 2600 ft. or 20 times the building height, whichever is greater.
Exception: For buildings whose mean roof height <= 30 ft., the upwind
distance may be reduced to 1500 ft.
Exposure C shall apply for all cases where exposures B and D do not apply.
Exposure D shall apply where the ground surface roughness, as defined by Surface Roughness D, prevails in the upwind diection for a distance >= 5,000 ft. or 20 times the building height, whichever is greater. Exposure D shall extend into downwind areas of Surface Roughness B or C for a distance of 600 ft. or 20 times the height of the building, whichever is greater.
Kzt = (1+K1*K2*K3)^2 (Eq. 6-3), where:
H = height of hill or escarpment relative to the upwind terrain, in feet.
Lh = Distance upwind of crest to where the difference in ground elevation is half the height of hill or escarpment, in feet.
K1 = factor to account for shape of topographic feature and maximum speed-up effect.
K2 = factor to account for reduction in speed-up with distance upwind or downwind of crest.
K3 = factor to account for reduction in speed-up with height above local terrain.
x = distance (upwind or downwind) from the crest to the building site, in feet.
z = height above local ground level, in feet.
The effect of wind speed-up shall not be required to be considered (Kzt = 1.0) when H/Lh < 0.2, or H < 15' for Exposures 'C' and 'D', or H < 60' for Exposure 'B'.
|Main Wind-Force Resisting System||0.85|
|Components and Cladding||0.85|
Note: this factor shall only be applied when used in conjunction with load combinations specified in Sect. 2.3 and 2.4. Otherwise, use Kd = 1.0.
- An enclosed building is a building that does not comply with the requirements
for open or partially enclosed buildings.
- An open building is a structure having all walls at least 80% open.
- A partially enclosed building complies with both of the following conditions:
- the total area of openings in a wall that receives positive external pressure exceeds the sum of the areas of the openings in the balance of the building envelope (walls and roof) by more than 10%; and
- the total area of openings in a wall that receives positive external pressure exceeds 4 sq ft or 1% of the area of that wall, whichever is smaller, and the % of openings in balance of the building envelope does not exceed 20%.
For buildings with roof angle > 10 degrees: h = (hr+he)/2
For buildings with roof angle <= 10 degrees: h = he
- The building mean roof height, h, must be <= 60 ft.
- The building mean roof height, h, does not exceed the least horizontal dimension, L or B.
|Roof Angle,θ||Building Surface (Zone)|
|Partially enclosed buildings||+0.55, -0.55|
|dings +0.55, -0.55
|Per Sect. 188.8.131.52, for a partially enclosed building containing a single, unpartitioned large volume, the GCpi coefficients shall be multiplied by the following reduction factor, Ri:
Ri = 1.0 or Ri = 0.5*(1+(1/(1+Vi/(22800*Aog))^0.5)) <= 1.0
|Exposure Category||α||zg (ft)|
|Category||Non-Hurricane Prone Regions
and Hurricane Prone Regions
with V = 85-100 mph and Alaska
| Hurricane Prone Regions
with V > 100 mph
- U.S. Atlantic Ocean and Gulf of Mexico coasts where the basic wind speed is > 90 mph.
- Hawaii, Puerto Rico, Guam, Virgin Islands, and American Samoa.
Disclaimer: This wind load calculator software and the resulting wind load calculations are not intended to be used for the design of actual structures, but only for schematic (preliminary) understanding of structural design principals. For the design of an actual structure, a competent professional should be consulted who can assist with calculating wind loads on structures and design schematics.
‘Calculations courtesy of Alex Tomanovich, PE ’