Steel Deck In Large Floors Below Ground ? Your Experience 5

[IJR]

Friends

I wonder if anyone of you has designed/used composite steel-concrete decks for large floors below ground. We usually use concrete moment frames/walls and solid floor slabs on the concern that thinner concrete in steel decks will not provide good rigidity and diaphragm action, and that connection to walls could cause leakages.

Please share your experiences. Thank you in advance.

respects
ijr

 

[HTURKAK]

You have allready well explained the reason for solid slab..

( ...connection to walls could cause leakages ) ??

Will you pls . be more specific? What is the depth of the underground str.? detail of perimeter wall? a sketch would help..

 

[KootK]

1) This has been done successfully in the past even if it's not ideal from a structural / durability perspective.

2) The axial stresses in the slab resulting from the basement walls wanting to push inwards tend to still wind up being comfortably low.

3) As you've identified, diaphragm strength and stiffness may require more attention that one might normally give those things with a beefy CIP slab. That, particularly at the main floor slab which usually winds up being a heavily loaded transfer slab from a lateral design perspective. Backstay effect and all that. You'll want discrete collector elements flying around, carefully designed to do their jobs.

4) Your subterranean decks will tie into the interior faces of your basement with an edge angle etc and, thus, ought not cause any waterproofing difficulties.

5) I don't super love steel in vehicular parking situations for corrosion reasons but, again, it's certainly been done before.

 

[canwesteng]

Point loads from wheels might be hard to resist with slab on deck, if it's a thin slab... assuming the underground is parking, could well not be.

 

[le99]

The steel structure in a high hunidity environment is more of a concern than rigidity.

 

[JLNJ]

If you have point loads (such as those from vehicles) you probably should just consider the deck sacrificial rather than composite.

 

[KootK]

The humidity thing has me thinking but there's a whole AISC design guide dedicated to steel framed parking decks (above grade). There must be some way to handle the cars reasonably.

 

[canwesteng]

DG 18 is recommending concrete on form deck, not composite deck. It doesn't have a lot of meat for design info, but it would be the same way you design any other slab, neglecting the deck below.

 

[KootK]

This is an old thread where we discussed similar things for a non-parking subterraneous basement: Link

 

[KootK]

This is/was SDI's position statement on composite deck in parking structures. It's been superseded but I couldn't determine by what exactly. Perhaps, it's been superseded by retracting their support for the concept altogether. Certainly, paragraph #3 creates a daunting impression.

 

[IJR]

KootK

my additional thanks for your amazing support.