slab on grade

[MelStud]

How does the height of the building affects the foundation type? I have a 26' pre-engineered building, but I am not sure if it can be supported on a slab-on-grade, or if it is better for it to be supporting on footings. Does this depend entirely on the loads/reactions?

 

[jayrod12]

You need to resist the uplift load from the building. This takes a lot of concrete in some cases.

 

[KootK]

Even for downward loads, you're not likely to end up truly supporting the building on the slab on grade. Three common systems are:

1) Grade beams and piles.

2) Piers and shallow footings.

3) Slab on grade with a perimeter turned down thickening that acts as a shallow footing, perhaps with some local load sharing to the slab on grade.

#3 may be what you're thinking of. In all cases, it depends on loads and settlement potential among other things.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[CANPRO]

a while back, kootk suggested a book for the design of pre-eng building foundations. "Foundation and Anchor Design for Metal Building Systems" by Alexander Newman. I purchased the book and can confirm that it is an excellent reference. It covers various foundation types and items to consider in selecting a foundation. Reactions obviously play a role in the selection and design, but the foundation type can also be affected by the end-use of the building, soil type and contractor/customer preference (among other things).

 

[Trillers]

I have designed quite a few PEMB buildings in our region which is a high wind-speed (175+ MPH) region.

Except for a couple of low profile (less than 12' at roof apex) and short (less than 24' longitudinally) buildings we have always designed footings tied into the slab on grade.

Otherwise we would be required to have some fairly thick slabs with adequate reinforcement to withstand uplift and slab cracking from uplift.

Design an integrated footing/slab system - trust me - you will sleep better at night.