Edge Column PEMB

[Joe117]

Is there any way to do a 50' span pre-engineered metal building foundation having the main frame columns supported on the edge (next to 1.5" sheet ledge) of the slab if the footing does not extend past the slab? Wouldn't be able to count much of the footing area that extends underneath the building slab for allowable bearing pressure because of eccentricity? Or am I going crazy?

 

[dik]

I've done many small PEMBs supported on a stiffened slab edge; is that similar?

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[HTURKAK]

The simplest reasonable foundation for this case, DOWN TURNED SLAB.

The figure ( copy and paste ) from Metal Building Systems ( by Alexander NEWMAN )

 

[Joe117]

So there’s never a good place to add HVAC equipment to a PEMB if there wasn’t cooling to start with? Guess a packaged unit on the ground is the only answer?

 

[dik]

With PEMBs, there's never a good place to add almost anything, if it wasn't there to start with. On one project, they did a redesign for adding sprinklers.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Joe117]

How did they do that? Busted out concrete to put a new frame up to hold sprinklers? I'm guessing the CM/GC/builder was very understanding..

 

[dik]

They were added to the PEMB... they didn't think it was necessary to add them to the slab. It was just the added weight that prompted the re-design. I didn't do a re-design of the foundations for the added sprinklers.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Ron247]

For clearspans 60' and less, or modular PEMBS that have interior columsn 60' or less, you can generally get a turned down slab to work as shown by HTURKAK. Turn-downs don't do well over 60' columns span. The work real good on 40' and less. Once you design for uplift, soil bearing is generally ok unless you have crane loads on the column.

The grade beam is like part of your foundation in the turn-down scenario. The foundation is more of a T-shape.

 

[phamENG]

I'm confused - are you asking about foundation design, or adding HVAC? Or are the two related in an as yet unstated way?

Ron247 is dead on with the foundation. Unless it's being used for crane operations or it has a 60psf+ snow load, uplift will control the size of the footings. It comes down to detailing the steel in the stiffer portions of the slab (turndowns, etc.) to resist it.

I've seen a few RTU additions to PEMBs - they cut a hole in the roof, put 4 pipe columns up from the slab with a platform, and patched the roof around it. PEMB didn't take the new loading. It's usually best to assume they have zero residual capacity.

 

[dik]

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik