High Wind Loads in Arctic

[gmf]

I am designing a small but important building for a small community in Canada's arctic. I am aware that the winds in the area are quite heavy. To begin the design, I obtained climatic data from the meteorological service in Canada as per the national building code (data was not provided in the climatic tables available with the building code). The results returned an hourly wind pressure for 1 in 50 probability of occurrence of 1.23 kPa. The building is on a hill, so an adjustment factor of 1.3 should be used for wind speed up over a hill (based on hill geometry and the requirement of the building code commentary). I also have a set of old structural drawings (1987) for the original building we are replacing, which shows that they used a reference wind pressure of 2.2 kPa for a 210 km/h wind speed. It should also be known that the original building’s roof had blown off at one point in its life.

My question is an opinion/judgement question: What reference wind pressure should be used? The higher one because it is shown on a set of old structural drawings, or the lower which is based on current building code requirements and climatic data?

 

[racookpe1978]

The older one has been "proved" with time, it is more reliable because it has been tested under real world conditions - by definition.

The older one sets a more strict requirement, which will require more material or thicker material, and thus will be more expensive.

The newer criteria smells to all holy heaven as based on theory and assumptions and probabilities of assumed conditions if certain theories are assumed correct part of the time. Maybe they are right.

 

[JStephen]

My thinking- for a small remote structure, the major costs will be mobilization, freight, labor- and a little extra material cost would be much less significant- whereas the cost of a rebuild would be significant- so go for the more conservative design.

 

[TXStructural]

Take JStephen's advice.
Code loads are minimum design loads. ("Minimum Design Loads for Buildings and Other Structures")
Do not be afraid to design for higher loads. Engineering judgement includes deciding how to design a structure which will serve the intended purpose and provide good service to the owner.

 

[BAretired]

If the roof blew off using a wind pressure of 2.2 kPa, you might want to consider using a q[sub]50[/sub] value even higher than that.

I worked on the DEW line in 1955. One site that I visited had tremendously high winds but they were quite local due to an unusual configuration of the nearby mountains. When it blew, the wind went through that site like a freight train. In the winter time, it was impossible to stand up when the wind was blowing. Visibility was virtually zero because of blowing snow. Ropes were installed between buildings to prevent people getting lost going from one to the other. The natives named the place "Blow River".

BA