Wind load on an irregular building (picture attached) 4

[GalileoG]

Hi all!

I could really use your help with this one.

I have a building (see attachment) with an irregular shape to it (both in height and floor plans.) I am designing as per the National Building Code (Canadian) and have not the slightest clue as to how approach this building when it comes to wind.

I am going to tell you how what I think the approach should be but would REALLY appreciate guidance on this matter.

When the wind travels in the direction "C", the building is a "high-rise building as per NBC" and should approach it in that manner. When the wind approaches in the direction "A", it is a low-rise building as per NBC" NOTE: the building is not cantilevered at this location, it is on grade as well.
Am I correct so far?

How about when the wind is coming from "D"? The lower roof is a "low-rise building" and the side of the building to the left of it as well, but not the building face directly above the lower roof.

Ugh so confusing! ;(

 

[asixth]

I'm not familiar with the Canadian codes, but if I were designing this building, for wind in direction A and C, I would be trying to transfer the wind load into the embankment by anchoring.

If the code classifies this building as a highrise, how does that differ your analysis and design? Are you required to take into account dynamic effects or are the pressure co-efficients altered? If the building is a highrise, I would be inclined to send it away for wind tunnel testing.

As for wind in directions B and D, I would calculate the wind pressure, the elavation area, distrubte the force to the floor diaphrams accordingly and ensure the lateral system has the capacity to transfer this to the foundations.

I would also be mindful that the embankment may add some additional topographic effects if the hill is large enough.

 

[ali07]

See commentary of NBCC 2005, it gives i think table I-16 for highrise building. Building should be highrise in all aspects, be conseravtive if there is a slight difference. Check deflection of building to max 1/500 of building height, it's max as per Canadian Code, but check 1/10 period when checking defelection and 1/50 when designing for diaphgram. Also check for earthquake loading.

 

[parrot77]

Sorry I cannot comment on the Canadian codes as i practice in Ireland. But on inspection perhaps the most important feature of the building with respect to wind loading will be significant uplift presssures on the cantilevered section. Signigicant negative pressures will build up on the underside og this 'canopy'

 

[asixth]

parrot77,

At first I thought this as well but according to Clansman's oringinal post, this building is not a cantilever.

 

[csd72]

Treat the small part in section D as a separate building. And then ignore it when analysing the main building as it will have neglible effect on the wind pressures.

Directions B and D would then be basically the same, take the worst of the 2 and apply it in both directions.

B is much worse than A, so ignore A and just take the wind load from B in both directions. This assumes that there are no major earth retaining forces, if there are then direction A may then be critical.

 

[GalileoG]

Thanks all! I really do appreciate it!

csd72,

Bearing in mind that under that cantilever is grade, wouldn't the "Cantilevered" portion in direction B and D act as a low-rise whereas the non-cantilevered portion act as a "high rise" if I were to assume they are independent structures?

Thanks again!

 

[csd72]

I would design the whole width using the worst of the 2 criteria.

 

[GalileoG]

Understood.

Thanks again to everyone.

*starts issuing stars*