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Collar Joint Question

Collar Joint Question

Collar Joint Question

(OP)
I'm working on a parapet that's 48" high.  It's 3 wythes thick with the inner two wythes acting compositely.  The outer wythe is a veneer separated by a cavity.

ACI 530-02 and UBC say a 2" min collar joint for 5' height for the 2 grouted wythes.  I don't think we can go much less than that.  Also, the #4's @ 32 o.c. need at least 1-1/2 practically.  The architect wants 3/4" so he can put in headers.  With a 2" collar the headers don't span.  And says he can cut out around the vert. #4's to provide grout space around them.

Thanks for any suggestions.

RE: Collar Joint Question

how thick are your wythe's?  does a 48" tall parapet really need composite behavior?  Can one wythe be thick enough to get some rebar in it without using composite action?

RE: Collar Joint Question

A 4" thick brick wythe cannot be effectively reinforced, considering the small "d" dimension.

A 6" block could easily be reinforced and still provide the cavity with a thinner wall section than the doule brick plus cavity, plus veneer.

Dick

RE: Collar Joint Question

(OP)
The bricks are 3-5/8" wide.  So the two inner wythes with a two inch collar joint between them net out 9-1/4."

I suggested cmu before as you mentioned, Dick, but the archtiect said no.  He wants a parapet of only clay brick.  

Thanks very much for the comments.

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