Isolation Joint in Pre-Engineered Building w/ Hairpins

[rharting]

All,

i'm working on a small pre-engineered building foundation design where we are using hairpins to tie the concrete piers (in the NE so exterior foundations are 4' down) into the slab to assist in resisting the horizontal thrust. In addition, I was planning on tying the perimeter foundation walls to the sog as well with reinforcement. For ease of construction (it's a small warehouse), the foundation walls will be poured up to the finished floor and then the slab will use the wall as a pour strop.

Our typical details call for isolation/expansion joints between the slab and the foundation wall/pier, however in this instance I'm not sure it will do anything. Since the piers and foundation walls will be at the finished floor elevation, there will already be a construction joint between them (therefore crack control is not required). Since we are tying everything together, differential movement between the slab and the piers shouldn't really exist. It seems to me that the isolation joint would only do harm in this instance.

Any thoughts?

Thanks in advance.

 

[msquared48]

I generally use a monopour for small pre-engineered metal buildings (slab and footings poured as one unit), with the control joints set off the mainframe gridlines so they do not impact the hairpins.

Mike McCann
MMC Engineering