Column Bracing

[SteelPE]

I asked this question a few months ago and came up with a solution that suited my needs, but now I have the same question but asked slightly differently.

I have been asked to look at a metal building that needs new siding and roofing. This is due to a small change in use of the building that will require the building to be heated. The idea/plan I have from the architect has them changing the metal siding and screw down roofing to insulated metal panel (yes, they plan on using metal panel on the roof).

The question I have is in regards to column bracing. In a new metal building that utilizes insulated metal panel, does the metal building manufacturer assume the perimeter girt/insulated metal panel systems brace the columns against weak axis buckling?

 

[straub46]

I used to work for one of the larger metal building companies. They will consider the IMP/girt to brace the outside flange of the column, and will add discrete flange braces (think rafter fly braces) to the girts to brace the inside flange as needed by design. The wall panel being IMP vs standard metal siding made no difference in how the system was considered to brace the columns.

I think there's a requirement in AISI that requires fasteners to be spaces less than 12" on center (I can't remember the exact number, you'll want to check that) in order for panel to be considered effective in bracing the girt. You'll want to verify that the IMP connections to the girt will be that close together.

Go Bucks!

 

[SteelPE]

I think there's a requirement in AISI that requires fasteners to be spaces less than 12" on center (I can't remember the exact number, you'll want to check that) in order for panel to be considered effective in bracing the girt. You'll want to verify that the IMP connections to the girt will be that close together.

I thought the 12" spacing was for an empirical design method for the girt systems. In any event, they typically only use size joint attachments for these system.... and with the male/female ends of the panels, each panel is only connected to the perimeter girts on one side only.

I have the question into someone I know who used to program their software to see what he thinks.

Those braces on the interior flange I would call flange bracing and I always thought there were there to prevent LTB of the column section.

 

[straub46]

This is the 12" provision I was talking about, in order to use the code prescribed R value

Correct on the flange braces, but I would think you'd need the panel to be appropriately attached to the girts to get any real stability out of the system.

Go Bucks!

 

[SteelPE]

This is the 12" provision I was talking about, in order to use the code prescribed R value

Yes, this is the "empirical" method I was talking about. From what I recall, this method was based upon real world testing. I typically use the unbraced length charts that can be found in the AISI manual and avoid this method all together (because insulated metal panel doesn't comply with the criterial to use the R factors).