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I am working on a retrofit of a three story URM building. In detailing
the connection of a new moment frame to the existing lintel element,
frame placed within the open storefront of the building, I am concerned
about the effectivenes of any shear transfer connection I make.

The existing lintel is presently being opened up so I will ultimately
have more info about what is there but for now...

I can see a 13" wide 3/8" thick horizontal steel plate under the lintel
with rivets. I am assuming this plate is the bottom flange of a built up
member buried within the thickness of the 13" thick urm above.

I need to be sure that in plane loads from the wall above are going to
transfer to this built up member if I  make connection between the new
frame and existing 3/8" steel plate. Once this area is opened up I can
access the capabilities of the existing assembly but for now I am
interested in what others have come up against for this type of
connection.

Secondly, I am making all my diaphragm to wall connections from below,
the existing straight sheathing and hardwood flooring will remain
intact. When installing new continuous blocking, tension ties and shear
bolting, I am questioning the neccesity of providing new boundary
nailing. Per the UCBC, the limitation of the shear connection capacity
to the shear capacity of the diaphragm provides a connection strength
that causes shear yielding in the diaphragm. Will any new boundary
nailing compromise the shear yeilding mechanism of the diaphragm? Any
new boundary nailing of existing sub floor to blocks would be done from
below with a35's screwed into underside of sub floor.

Any comments would be appreciated.

Mark D. Baker
Baker Engineering