• To: "seaoc list" <seaint(--nospam--at)seaint.org>
• From: "T. Eric Gillham PE" <teric(--nospam--at)gk2guam.com>
• Date: Wed, 20 Jun 2001 08:47:31 +1000
```Bill:

I would check the ledger for the load case that you are describing -
combined tension (from roof uplift) and shear (from wall suction), but I can
see your point that it seems a bit conservative from a C&C point of view.

However, as I see it that is a possible loading condition, and should be
checked.

It would seem that the tributary area of the angle, both from the roof and
the walls, would be the governing factor, along with the designation of
MWFRS vs. C&C, which in my mind is tributary area controlled anyway.

If you have already designed the angle for 1) roof uplift and the
corresponding trib area and 2) wall suction and the corresponding trib area,
and these were done separately, then to do them together results in a larger
trib area (roof+wall), which through some rational engineering judgement,
would result in lower coefficients used to compute the wind pressure on the
roof and wall.

Not sure if this makes sense, but in general it is how I would approach it.

Regards,

T. Eric Gillham PE

-----Original Message-----
From: Bill Polhemus [mailto:bill(--nospam--at)polhemus.cc]
Sent: Tuesday, June 19, 2001 9:36 PM
To: SEAINT

I'd like some opinions.

I'm putting the finishing touches on a little Mathcad template that I'm
using to verify the designs of ledger angles used as collector elements for
roof diaphragm shear transfer to the wall. I compute all the various load
combinations that I can think of including wind load, and come up with a
load on each fastener depending on spacing.

It occurs to me, that there is the possibility of simultaneous tension and
shear on the fastener if you consider the wind load acting outward on
opposite walls, but since this is a fastener (a "component") I'm not sure
how I would compute this. Such a load is transferred into the fastener by
simultaneous loading of the roof and wall, and that's really not the
philosophy behind "components and cladding." The C&C loads are not given a
"sense" (plus or minus) as they are for MWFRS.

I'd like to know how any of you handle this in your calculations (yes, I'm
making calculations EVEN THOUGH I don't have to submit them to the Code
official! Imagine that!)

Regards.

William L. Polhemus, Jr., P.E.
Polhemus Engineering Company
Katy, Texas
Phone 281-492-2251
Fax 281-492-8203

*
*   This email was sent to you via Structural Engineers
*   Association of Southern California (SEAOSC) server. To
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
*   send to the list is public domain and may be re-posted
*   site at: http://www.seaint.org

*
*   This email was sent to you via Structural Engineers
*   Association of Southern California (SEAOSC) server. To
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
*   send to the list is public domain and may be re-posted