Internal Pressure - Two Sided Warehouse?

[BenAustralia]

I have a portal frame warehouse to design. 45m square. Framing spacing of 9m.

Only two sides of the warehouse have sides, the other two are completely open. One end wall and one side wall.

Can I develop internal pressures?

There is nothing referenced to this situation in the Australian Codes, so I'm not sure. I don't want to assume an internal pressure if it can't happen, big difference in sizings.

Thoughts?

 

[ron9876]

I think ASCE7 would say no but never made sense to me. If wind is at 45 degrees it seems to me there must be positive pressure on the interior and negative pressure on exterior.

 

[RFreund]

You say you have a portal frame but then one side wall and one end wall. Is this L-shaped?

I think you have windward and lee ward pressure, yes. But internal pressure is slightly different. Normally you assume the structure is like a large wall in that there is wind on the front face (windward) and 'suction' on the rear face (leeward) with some pressure that can get inside and push on the walls (internal). However once you get a large opening on the front face of the structure wind can enter through this opening (like a balloon effect). So now you have windward pressure on the front face, leeward pressure on the back face and also this what is essentially a windward pressure on the inside back face of your rear wall (internal).

EIT

http://www.HowToEngineer.com

 

[sturr]

Using ASCE 7-05, your building would need to be defined as "open" for there to be no internal pressure. This would require 80% of each wall to be open. You most likely have a "partially enclosed" building as defined by ASCE, this means higher internal pressures than a "closed" building. This will affect the roof pressure. With respect to the walls, I agree with RFreund.

 

[UcfSE]

I would look at the definitions for each enclosure case in your code and follow them. I've had some non-intuitive results myself on occasion, but then, that's how the numbers worked out.

 

[BAretired]

If, by internal pressure, you mean pressure on the interior surfaces, the answer is yes.

BA

 

[steellion]

You won't have an "internal" pressure, but each wall will have superimposed windward and leeward pressures to consider, similar to a screen wall.

 

[BenAustralia]

Internal pressure as defined by our standards.

Building is L shaped with a normal gable warehouse roof.

Wind hitting either of the walls first would result in standard roof, windward and side wall pressures. There is no leeward wall to have pressure on, only the inside face of the windward. Would this experience the same leeward suction as a normal building even though wind coming over the roof is met by an open space? I.e. Suction caused here has further to "travel" back to a surface.

As for wind entering the open sides first. Normal roof pressures. Windward pressure on the internal back wall. Probably no wall suction. Unsure on pressure pushing roof up from inside?

 

[BenAustralia]

Our standards basically have extensive coefficients for rectangular enclosed buildings, with allowance for dominant openings. Or it has free roofs and hoarding coefficients in the Appendix.

There is no case for open type buildings really.

Most of the coefficients come out fine. Its just the internal pressure (inside face of windward and inside face of roof) when wind hits a walled side first, and the internal roof pressure when it comes in the open side and hits the back wall first

 

[hokie66]

Ben,
Not looking at the Standard at the moment, but have you tried the Appendix section on canopies, awnings, etc? That may be appropriate for the internal pressures.

 

[BenAustralia]

Yeah, nothing that seems appropriate though.