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Precast connections with no bearing plate

Precast connections with no bearing plate

Precast connections with no bearing plate

(OP)
Hi,

I saw some connection designs using only welded rebar cage with no steel plate in the precast concrete parking garage.

These happened to the bearing connections like double tee-litewall, load bearing spandrel-exterior column and inverted beam-column.

I wonder if these details are common.

And, isn't there any potential problem?


Thanks for your comment in advance!

RE: Precast connections with no bearing plate

Concrete on concrete bearing connections aren't too uncommon in precast design. The biggest reason to use steel plates is you can weld them together for the required ties for structural integrity. If you can satisfy structural stability elsewhere then there's nothing inherently wrong structurally with concrete on concrete bearing. The other main issue though is any rotation or movement between the members can damage corners. Providing chamfers or armoring corners to prevent spalling would be one solution; more common would probably be a rubber or composite bearing pad.

Something lighter like a double tee I could see working without a bearing pad; however a inverted tee seems like it would be hard to prevent issues. Are you sure there's not a bearing pad in there?

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
https://www.facebook.com/AmericanConcrete/

RE: Precast connections with no bearing plate

(OP)
TME,
Basically, you mentioned everything I am concerned about.
You need to take care of many factors including 'structural' viewpoints.
So, can you accept this design if somebody wants to use it for inverted girder bearing connection
when you consider everything?

RE: Precast connections with no bearing plate

Would I accept it? Probably not. Could it be done successfully? Sure.

Being in the precast industry has taught me a few things; one is to be comfortable taking a precast design to 100% of structural rated capacity but avoid anything ever that could damage the appearance of the precast. Color variations on architectural concrete, cracks on exposed faces, spalling, holes, anything that looks damaged usually results in repairs and/or rejected precast.

Thus, I work very hard to avoid cracking or anything that can spall or break in an exposed area. For a parking garage I'd want a bearing pad on pretty much everything. The costs of these pads would be far outweighed with just one rejected or damaged precast element. I'd also make sure that everything was connected as required by ACI 318.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
https://www.facebook.com/AmericanConcrete/

RE: Precast connections with no bearing plate

(OP)

Thank you very much for your opinion, TME!

I am looking forward to other engineer's opinion.

Thanks!

RE: Precast connections with no bearing plate

You've already heard from an expert but, sometimes, one does value a consensus. To that end, I agree with TME completely.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

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