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eng003 (Structural) (OP)
24 Sep 13 20:59
Looking at 2 story 8" cmu structure to have wood floor & roof trusses. Floor trusses likely be 24"+/- depth. Interested in opinions/reccomendations on detailing floor truss connection to wall i.e. top bearing, bottom bearing, hanger, ledger, pocket, moisture break, cmu bond beam verse cip beam...Also I recall reading limitations of wood framed diaphragms in combination with masonry walls? any thoughts on this...?
jayrod12 (Structural)
25 Sep 13 9:13
Make sure your floor sheathing connection along the walls parallel to your floor trusses can transfer your required diaphragm load. We generally do a bolted ledger (2x8 or so) and then spec the screwing pattern.

We don't do masonry walls with wood floors here (Manitoba) it's usually either CMU walls and hollowcore, or all framed as wood especially at 2 stories. However we are in a "non-seismic" zone.
BAretired (Structural)
25 Sep 13 14:03
Could be done either way, but top bearing would be my preference.

BA

jayrod12 (Structural)
25 Sep 13 15:07
And I agree with BA, Top chord bearing open wood web trusses is how we've gone typically on all jobs.
msquared48 (Structural)
25 Sep 13 19:17
I agree too. Makes the transfer of the diaphragm forces a lot cleaner, among other things.

Mike McCann
MMC Engineering

jittles (Structural)
25 Sep 13 19:19

Quote (eng003)

Also I recall reading limitations of wood framed diaphragms in combination with masonry walls? any thoughts on this...?

You may be thinking of the special requirements for out of plane attachment? This is covered in section 12.11 of ASCE 7-05.
eng003 (Structural) (OP)
25 Sep 13 20:34
Thanks all. Top chord bearing was my preference too; I agree it is easier to transfer the diaphragm forces and I haven't seen any deeper truss hangers to even do bottom bearing? Probably go with a 2x8 ledger attached with cast-in-place, expansion, or epoxied anchors any thoughts/reccomendations? Also, regardless of whether I can make the numbers work for say an 8"x16" or 8"x24" continuous cmu bond beam at floor level to take the diaphragm chord forces...looking for others rules of thumb for when they move to a cast-in-place beam instead. Thanks
jayrod12 (Structural)
26 Sep 13 9:05
If you can get the guys to do cast-in anchors then by all means do it. More than likely they won't want to. My next option would be epoxied anchors not a huge fan of expansion for some reason, I'm just not sold on them.

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