Uplift on Foundation for PEMB
Uplift on Foundation for PEMB
(OP)
I am doing the foundation design for a Pre-Engineered Building and as any of you know that has done this type of work, the shear/thrust and uplift are always killers. Before, I used to just increase the size (perimeter and/or thickness) of the pad footing until I exceeded the uplift reaction (after taking the 40% reduction, of course).
However, I'm starting to wonder why I never considered part of the wall footing that is tying into the pad footing. At first I thought maybe I could consider the portion of the wall footing from bay to bay (so if I have 20' col spacing, i would using 20' of wall footing) but that seems like too much. Is there any sort of rule-of-thumb to go by as to how much of that wall footing (and for that matter the grade wall also) you can consider to counteract the uplift?
Thank you in advance for the help.
However, I'm starting to wonder why I never considered part of the wall footing that is tying into the pad footing. At first I thought maybe I could consider the portion of the wall footing from bay to bay (so if I have 20' col spacing, i would using 20' of wall footing) but that seems like too much. Is there any sort of rule-of-thumb to go by as to how much of that wall footing (and for that matter the grade wall also) you can consider to counteract the uplift?
Thank you in advance for the help.






RE: Uplift on Foundation for PEMB
In some cases in Florida, I have used 5-8' of slab on grade weight (16' diameter max) in interior column locations as well, and weight of soil resting above the footing and slab on grade.
RE: Uplift on Foundation for PEMB
RE: Uplift on Foundation for PEMB
I have also considered using the shear capacity of the soil above and next to the footing.
RE: Uplift on Foundation for PEMB
RE: Uplift on Foundation for PEMB
I wouldn't use the entire 20' length of wall footing weight to counteract uplift, but I would take advantage of it. Maybe 5 feet in each direction, plus soil/slab-on-grade weight over the footings. It's whatever you feel comfortable with and can rationalize with sound engineering, realizing that it's unlikely the building footings are going to actually pull out of the ground and fly away.
RE: Uplift on Foundation for PEMB