Steel deck with thick concrete topping
Steel deck with thick concrete topping
(OP)
I encountered a special situation. It is a c.i.p. cooling tower basin bottom slab (I posted a thread a few days ago about the cooling tower) supported by wide flange steel beams. The depth of the slab is 12”, in which I use 3” deck. Now I found the typical composite beam section tables do not cover the sections with this thick of concrete topping. Any suggestions to deal with this?
Thanks in advance!






RE: Steel deck with thick concrete topping
DaveAtkins
RE: Steel deck with thick concrete topping
RE: Steel deck with thick concrete topping
RE: Steel deck with thick concrete topping
Maybe this is a place for good old fashioned formwork.
RE: Steel deck with thick concrete topping
RE: Steel deck with thick concrete topping
Regards,
Lutfi
www.cdeco.com
RE: Steel deck with thick concrete topping
RE: Steel deck with thick concrete topping
Bermuda allows galvanized rebars only. I do not design for galvanized bars. I know some DOTs use epoxy coated bars. I heard that they are not all that successful in fighting corrosion. I do not have first hand knowledge of this.
I agree about reduced bonding due to zinc finish. However, I am sure that you can account for the bond reduction.
Regards,
Lutfi
www.cdeco.com
RE: Steel deck with thick concrete topping
RE: Steel deck with thick concrete topping
The bond between concrete and galvanized rebar takes more time to come up to strength (compared to plain rebar). However required lap splice length for both galvanized and plain rebar is the same (See ACI-315, Paragraph 2.7.1) see this page 5 of this link
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Totally agree with Lutfi about the corrosive nature of cooling tower water. Suggest that you take every precaution that he has recommended - for all the steel in your project.
www.SlideRuleEra.net
RE: Steel deck with thick concrete topping
RE: Steel deck with thick concrete topping
I like the idea of designing the beams as noncomposite. If this unshored or shored? If it's unshored, then your beams will be honkers for the wet concrete weight anyway so I'm not so sure you'll save that much by going composite. Not knowing your structure, this is obviously just a speculation.
Like some of the others, I'd be a bit concerned about corrosion. I've done this several times and went CIP concrete every single time, even for steel jobs.
DBD
RE: Steel deck with thick concrete topping
Any blemish, scratch or other damage to the coating will corrode at an accelerated rate to the point that brittle fracture becomes a danger. Because of this some states states will not allow the use of epoxy-coated bars."
The office I just left (going back to school yet again!) stopped using epoxy coated rebar in all parking garages for this very reason.
DBD