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RE: DSA Mech. Roof Equip., (Again)

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I guess I missed Doug Mayer's response the first time around. Anyway, got it this time- thanks for the info. Doug.

Larry Hauer S.E.


From: "Doug Mayer" <doug.mayer(--nospam--at)taylorteter.com>
Reply-To: <seaint(--nospam--at)seaint.org>
To: <seaint(--nospam--at)seaint.org>
Subject: RE: DSA Mech. Roof Equip., (Again)
Date: Mon, 15 Jan 2007 11:32:48 -0800

Larry,

Weird...I responded to your post, but I guess it didn't go through. Anyway, here is my response again.

I am betting the DSA reviewer is looking at the paragraph in section 1632A.2 that states:

"A continuous load path of sufficient strength and stiffness between the component and the supporting structure shall be verified. Local elements of the supporting structure shall be verified for the component loads where they control the design of the elements or connections."

However, the reviewer probably forgot to read the end of that paragraph which says that "...modifications to Rp due to anchorage conditions need not be considered." So, I would agree with you that the existing roof framing does not need to be checked for loadings based on the modified Rp.

If the reviewer still insists, ask him/her to specify the code section that explicitly states this requirement. If they cannot do that, they are required to yield to your engineering judgment. If they do not yield, ask to see their supervisor and make your case to them. However, if the existing roof members can absorb the increased loading, you might consider just doing it instead of ruffling some feathers. Hope that helps.

Doug Mayer, SE
Structural Engineer

TaylorTeter
Partnership

7535 North Palm Ave., Suite 201
Fresno, CA 93711

(559) 437-0887 Ph.
(559) 438-7554 Fax
doug.mayer(--nospam--at)taylorteter.com
 

-----Original Message-----
From: Larry Hauer [mailto:lrhauer(--nospam--at)hotmail.com]
Sent: Monday, January 15, 2007 11:19 AM
To: seaint(--nospam--at)seaint.org
Subject: DSA Mech. Roof Equip., (Again)

I didn't get any responses to the below message I sent out last Friday, so I
thought I would try again.

I am dessigning the support of two pieces of roof top mechanincal units
added to
an existing California school building, (DSA job). The equipment has
vibration
isolators and is to be supported by a braced steel framed platform with the
top
of the platform about 1'-6" above the exsitng roof. The platform will be
supported by tube steel stub columns welded to the exsting roof WF beams.

Per Table 16A-O of the '01 CBC, the a-p and R-p values I am using are per
Item
3-C with an a-p of 2.5 and R-p of 3.0 EXCEPT that footnote #14 requires an
R-p
of 1.5, (resulting in very large horizontal forces). The DSA plan checker
says
that this force must be used for the design of the entire system, including
the
existing roof framing. I contend that it is only the attachments and
anchorage
based on footnote #5 of the same table.

Anyone out there dealt with DSA on this issue before?

Thanks in advance,

Larry Hauer, S.E.

_________________________________________________________________
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_________________________________________________________________
The MSN Entertainment Guide to Golden Globes is here. Get all the scoop. http://tv.msn.com/tv/globes2007/?icid=nctagline2


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