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Re: Shot Pin Boundary Nailing

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Don - There are potentially two issues of concern with this system. 

First, mixing shot pins with a nailed, panelized roof results in a diaphragm
that may have no available test results for its shear capacity. Shot pins in
steel are likely far more stiff and deform differently than nails in wood,
so you may not have a diaphragm that performs reliably once it begins to
yield. You should consider adding a wood nailer to the top of the TS ledger
to create a diaphragm that complies with ICC-ES Reports or diaphragm
configurations in 2306 of the IBC. 

Second, the steel plates embedded in masonry walls are invariably going to
be misaligned with eachother unless you can find a perfect mason. So when
the TS is held up to be welded to the plates, there will likely be gaps
between the TS and the plates due to the misalignment and it will be
difficult to fillet or flare bevel across those gaps. 

In the 1992 Landers earthquake, a modern big box had a similar embedded
plate detail that contributed to its partial collapse. In essence, the
ledgers were not properly welded to the embeds in the wall due to the gaps
between the ledger and the embeds.  For photos, see page 4 of the Commercial
Property Owner's Guide to Earthquake Safety in the 1998 edition. That pic is
now on the cover of the 2006 edition. FYI, Fred

From: <bruckmandesign(--nospam--at)>
Subject: Shot Pin Boundary Nailing
To: seaint(--nospam--at)

I just received drawings for a one story big box retail store with a hybrid
roof of Vulcraft joists and panelized roofing.

At one area, the engineer has specified a boundary nailing of 2 lines of
shot pins @ 2 1/2" o.c. into a TS8x2 which is then field welded to a 12" x
12" steel plate w/ (4)3/4" ABs into masonry. (Strangely, there is no callout
for the shank diameter of the shot).

First, although I've not built such a system before so I can't say I'm any
kind of expert in hybrid diaphragms, I've never seen such a detail, and it
just intuitively sounds wierd.  Is this common?  Seems like a difficult way
to achieve a diaphragm transfer to me. 

Anyone used such a BN connection?


Fred Turner, Staff Structural Engineer, California Seismic Safety
Commission, a public policy advisory agency, Turner(--nospam--at), 1755
Creekside Oaks Dr. #100 Sacramento, CA 95833 Phone: 916-263-5506 Ext. 227 or
916-263-0582 Fax: 916-263-0594  

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