Load Transfer Mechanism of Pre-eng. Frame into foundation

[Baffled Engineer]

I have a 120'x80' pre-engineered frame building. The moment frames are 80' long at 20' o/c. I am designing the foundation for this building and what was proposed for the foundation was a slab-on-grade with perimeter thickening (the estimated cost of the building was based on this foundation type and cannot be easily changed).

My question is how to transfer the lateral reactions of the frame which is about 50 kips factored outward thrust.

I was initially planning on using hairpins to transfer the lateral forces into the reinforced slab-on-grade and make the reactions from each end cancel each other. However, there is a full depth drain in the middle of the building running perpendicular to the frames from building end to end which makes the slab-on-grade somewhat discontinuous. There is a thickening and reinforcing around the drain but I'm not sure if it's typical to design this to transfer the tensile forces.

I was also considering transferring the lateral reactions using the interface friction between the slab and the soil, but unfortunately a vapour barrier is required beneath the slab which I believe will make the interface friction small and negligible, or the friction may possibly rip the vapour barrier and negate its effectiveness.

I would appreciate what your thoughts are on this and how to deal with the lateral load transfer in an economical way.

Thanks.

 

[BAretired]

An 80' long tie beam is probably the most economical solution, but it has to jog around the drain. This requires a U-shaped section at the drain location which is capable of resisting the moment from the 50k thrust.

BA

 

[jayrod12]

I've also used Dywidag rods as tension ties at a depth below the trench drain. This gave them the ability to enclose the building prior to pouring the slab.

 

[WARose]

If you can't get a tie beam to work, you may have to have column footings deep enough so the passive pressure can take it out. The footings handle the OT (through bearing pressure) as well.