Monolithic Concete and Slab Foundations
Monolithic Concete and Slab Foundations
(OP)
I have seen a lot of metal building designed with a footing integral with concrete slab (monolithic). Most metal buildings that are designed for southeast locations have a large uplift on the foundation due to wind. I usually design the footing heavy enough the handle the uplift without taken into account any effects due to the slab. I have found that some engineers use a portion of the slab as well as a perimeter grade beam to resist uplift and use a hairpin to resist the horizontal forces. Does anyone know of any published literature other than a book called "Metal building Systems" that Clearly states the design assumption and amount of slab that can be used to resist uplift.






RE: Monolithic Concete and Slab Foundations
RE: Monolithic Concete and Slab Foundations
RE: Monolithic Concete and Slab Foundations
RE: Monolithic Concete and Slab Foundations
RE: Monolithic Concete and Slab Foundations
You may only consider the concrete between the columns as contributing if the concrete is integrally tied and also tied or keyed to the footing.
RE: Monolithic Concete and Slab Foundations
The column should be supported by a footing at some depth. In northern regions the frost depth is the minimum. The plan of the footing is projected up at 60 degrees. The weight of the soil, concrete, etc. enclosed by the 60 degrees is effective in resisting the uplift. The submerged unit weight should be used and factored down to determine the resistance in accordance with your building code. This applies to cohesionless soils only. It follows that the deeper the footing the more mass you will be able to use to resist the uplift.
The hairpins usually wrapping around the column anchor bolts going into the slab are designed to resist the kick-out (horizontal forces) of the frame. The length required is a function of the slab friction with the soil, steel in tension, development length, mass of slab to be mobilized, etc.
There are publications available for designing foundations for uplift and horizontal load. The foundation design type depends on the magnitude of uplift vs horizontal. I use to have some tables with standard designs, now where did I put them....