Wind Loads on Long Wall of Steel Building

Question

Wind Loads on Long Wall of Steel Building

Jared.S16 (Student)

(OP)

1 Jun 23 14:25

I am an engineering student focusing on structural engineering. For a design project this year, my group and I designed a very standard rectangular structural steel building (12 meters high, wide flange columns along the perimeter, one row of columns in the center, open web steel joists, braced bays, etc.). I have attached a sketch for reference. One thing that I had a hard time wrapping my head around was the fact that the wind acting on the long wall was assumed to be perfectly distributed to the short walls (i.e., each short wall takes half the wind load).

If I was to design a rectangular building in which the long wall was much longer than the short wall, would I assume that the entire wind load acting on the surface of the long wall would be evenly distributed to the short walls as well? I have attached a sketch for reference. I know that in wood construction, you can design partition walls that are perpendicular to the long wall as shear walls to take the wind load. In large structural steel buildings, they are often open-concept with no interior partitions or frames. How would you handle wind loads acting on the long wall in this type of situation?

I appreciate any responses even though this may seem basic to some.

Thank you.

https://files.engineering.com/getfile.aspx?folder=64b14139-1b74-4e36-9d23-0

driftLimiter (Structural) · Answer 1 · 2023-06-01 15:45:50

Generally for these types of structures the short direction frames are all lateral resisting elements. The wall elements between them typically span horizontally, so that distributed lateral pressure on the wall ends up being a distributed load up the column. The roof systems are composed of diaphragms generally in the form of horizontal bracing elements, these elements may be in every bay, or often a select few bays.

So the TL:DR answer is that for steel buildings of this type, the frames are generally laterally resisting and shear walls not not used anywhere.

Can check out AISC Design Guide #7 as well as Design Guide #25. These documents have a very nice overview of typical load paths, details, etc.

Jared.S16 (Student) · Answer 2 · 2023-06-01 17:53:34

That makes sense. So essentially, I would design each column in the long wall to resist its own tributary width of lateral wind pressure, and provided that the columns can withstand the moments applied due to the wind - then these "frames" in the short direction (consisting of the exterior column, the open web steel joist, and the interior column) would then act as a lateral resisting element?

In terms of designing a proper diaphragm for the open web steel joists, this is something that is typically done by the open web steel joists manufacturer, correct?

Thank you.

driftLimiter (Structural) · Answer 3 · 2023-06-01 18:26:42

Most likely the 'main frame' would have a girder that is wide flange so that with the columns it makes a moment resisting frame. It is possible to use a girder trusses in a moment frame but this approach has lost relevance and is generally not the preferred approach.

The frames don't just magically become a lateral resisting element, the entire frame including connections must be properly designed to resist the loading.

The design of a proper diaphragm is not in the scope of steel joist manufacturers and would need to be designed by the EOR (or another specialty engineer).

Typically they are composed of horizontal bracing, but a properly selected and fastened bare metal deck can also become a quite competent diaphragm.

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Wind Loads on Long Wall of Steel Building