RFI - Interior Slab for uplift resistance
RFI - Interior Slab for uplift resistance
(OP)
Would any of you have access to this paper "Uplift resistance of interior footings of low-rise buildings"
Or any other research that shows the contribution of a slab-on-grade to uplift resistance?
Imagine an interior column of a single story large warehouse type building. The columns have individual spread footings, soil above them and a slab-on-grade. How do you calculate the effective area of the slab for uplift resistance?
Do you calculate how much the slab can "cantilever" from the column in each direction based on the reinforcing provided? The compare this moment capacity to the moment produced by the self weight of the slab?
Or any other research that shows the contribution of a slab-on-grade to uplift resistance?
Imagine an interior column of a single story large warehouse type building. The columns have individual spread footings, soil above them and a slab-on-grade. How do you calculate the effective area of the slab for uplift resistance?
Do you calculate how much the slab can "cantilever" from the column in each direction based on the reinforcing provided? The compare this moment capacity to the moment produced by the self weight of the slab?






RE: RFI - Interior Slab for uplift resistance
If uplift is critical, I would prefer to drop the footing to engage the weight of soil or alternatively to use piles with pullout resistance. There is always the possibility that the slab could be removed at some time in the future.
BA
RE: RFI - Interior Slab for uplift resistance
RE: RFI - Interior Slab for uplift resistance
RE: RFI - Interior Slab for uplift resistance
RE: RFI - Interior Slab for uplift resistance
JWB
RE: RFI - Interior Slab for uplift resistance
I just add extra concrete and consider the soil where appropriate. Some of these structures go without slabs for a time as their owners run out of money, or other delays. I would just consider the slab and the sucking force as part of the factor of safety.
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: RFI - Interior Slab for uplift resistance
Be safe and just the extra concrete and just let the contractor b***h about it. In the end, it will probably end up being a small portion of concrete.
RE: RFI - Interior Slab for uplift resistance
ANY FOOL CAN DESIGN A STRUCTURE. IT TAKES AN ENGINEER TO DESIGN A CONNECTION."
RE: RFI - Interior Slab for uplift resistance
ANY FOOL CAN DESIGN A STRUCTURE. IT TAKES AN ENGINEER TO DESIGN A CONNECTION."
RE: RFI - Interior Slab for uplift resistance
Does that paper have a formulation based on testing? Do you have that paper and if so, would you mind sharing the design information pertaining to it?
RE: RFI - Interior Slab for uplift resistance
RE: RFI - Interior Slab for uplift resistance
And not to start another thread since this issue has been beat to death, but trying to get this equation to balance: W < 0.6D, it makes me feel a bit more comfortable using every ounce of dead load I can get my hands on (being liberal)...
RE: RFI - Interior Slab for uplift resistance
This only considers ultimate failure, not strain compatibility. In my scenario, the concrete would fail, but keep the structure from failing.
RE: RFI - Interior Slab for uplift resistance
They do have a formula for designing the uplift force of a footing without joints or shrinkage cracking. The formula is based on testing but is really a best fit of the data, with a large variation.
Ps=0.6 x Ks^0.2 x H^1.4 x b^0.56 x fr
Ps, is the uplift force on the slab at the first crack load (N); K, is the modulus of soil (N/mm3); h is the slab thickness (mm); B is the width of square footing (mm); and f, (=0.6 x fc'^0.5 (recommended this is factored down due to this be a non-structural element)) is the modulus of rupture (MPa). The ks values has very little bearing on the equation thus they suggest the use of 100 000 kN/m3 thus ks= 0.1. hopefully I copied this all correctly.
This is based on footing below the slab not integrated with the slab. When integrated with the slab you can take advantage of this as well as the strength will increase by the footing depth at the column location.
ANY FOOL CAN DESIGN A STRUCTURE. IT TAKES AN ENGINEER TO DESIGN A CONNECTION."