2 way concrete slab expansion joints

[englisa]

I have project that has a below grade heated parking, with surface parking as well as structures above. The main floor which will act as both the main floor for the buildings as well as at grade surface parking is a 2 way structural slab. The overall dimensions of this slab are 120m x60m, and I am wondering if an expansion joint (really a contraction or control joint) would typically be recommended in this case.

I know for slabs exposed to temperature change we would definitely have one, but since this one will be fully within the building envelope I am questioning if this would really be required since it will not see the temperature swing as it will be a controlled environment, although I have been told a general rule of expansion joints at 45m - 90m no matter what in concrete.

Also if so, I guess this joint should be carried through the cast-in-place foundation walls?

Thank you!

 

[dik]

I'd break the 120m should have a joint. I'd put one at about 1/5 span or use a double column system.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[hokie66]

A joint in the middle of the transfer floor would be my first thought. A line of double columns. But that has to be considered/coordinated with whatever structures are above.

As well, you will have a restraint shrinkage issue in the ground floor slab all along the basement walls.

 

[dik]

Near the PI with low shear...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[englisa]

Thanks for the advice, could you explain a bit more about what you mean by the restraint shrinkage issue in the ground floor slab along the basement walls and near the PI?

 

[Enable]

I have repaired a number of parking garages where heat was turned off during the service life to save costs (all apartment buildings owned by a private corporation). Issues are not trivial when that happens, at least up in snow country. I'd never bank on heating being a permanent thing in a parking garage. FWIW, in my repair work I typically see expansion joints between roof decks and the superstructure.

 

[dik]

I generally look at any transition or change in shape to see if there is a potential for movement.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[hokie66]

englisa,

Restraint shrinkage causes tensile stress in the slab because it is restrained by the already cast walls below. Therefore, to adequately control cracking in the slab requires added reinforcement. Sometimes, this problem is addressed by slip joints, locked in later. As to PI, I don't know what dik is talking about in regard to a movement joint.

 

[Tomfh]

Professional Indemnity (PI) insurance for when the slabs lock to the walls and the slabs crack anyway?

 

[hokie66]

Tomfh,
Yes, that could be it.