huangyhg

concrete slab on metal deck cracking. any insight?
we have a client who's elevated slab on metal deck and bar joists is cracking. thankfully it was not our design. it appears to be shrinkage cracks but i cannot find much information on control joint locations for elevated slabs. any help or direction to authoritative source would be appreciated. ken
where are the cracks and how big are they?
if they're not very large and are over beams and girders at column lines, then they're not unusual. assuming that it was screeded level, the slab's thinnest there. we tried everything at my old job and we could never get rid of these. they only caused major problems when we used sheet vinyl flooring. even tiny cracks cause little poofed up areas that we called ant trails in that kind of flooring.
i have not seen the slab yet. just doing a little back ground before i meet with the client at the site. ken
if the cracks are over a structural
normally you don't use control joints in elevated slabs.
need to know more. thickness of slab, reinforcing in slab, type of metal deck, spacing of joists, whether cracks are in any sort of pattern or random, width of cracks.
there was an article written titled "let it crack"
written by j. thomas ryan, pe.
could not find the direct link. i have pdf on disk, be glad to email it to you, or post it somewhere.
here is some info to back up you assessment.
thanks ironmon. the links were spot on. we are aci
i would add one caveat: get the owner's agreement and buy in before you just "let it crack". it has been my experience that owners most often expect to have an "uncracked" slab in new buildings.
i agree that in commercial buildings the crack can be filled and be covered with finished floor material although if it a hard material, a working crack sometimes can mirror thru.
it is a trade off between adding more steel or accepting cracks. get the owner's direction on what he wants.
visited the site today. most cracks appear to be due to negative moment over the beams where the joists butt. a few other random (shrinkage) cracks. contractor did a poor job locating his construction joints and selecting the direction of placement. i think he is ready for some help on the next one. thanks for the help. ken
in years past i have discussed this very issue with the metal deck manfgs. i was told it was not necessary to provide control joints. think about it, theres a solid layer of metal reinfg below the concrete slab (the deck) and typically the mesh will run thru the joinst anyway.

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