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RE: PEMB's and lateral deflection

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Bruce and Jim,
I had this conversation with some PEMB manufacturers a while back. The authors of Design Guide 3 intended this for use for the PEMB industry. They do a lot of work for that industry. Some manufacturers will balk, but the recommendations of Design Guide 3 are reasonable. There are no building code wind drift limits since this is a serviceability issue and is not a safety issue.

We create a one page performance spec for PEMB. The MBMA had some commentary stated that you should calculate lateral drift and some owners don't like it when the lights sway. The practice for better PEMB manufacturers is to limit lateral drift to h/30 for a 10 year wind, and h/100 if you have masonry. That is not restrictive enough. Again what is reasonable is contained in Design Guide 3.

You will have to put it in your specification. Don't just reference DG 3. It is not a manditory code. You can make it manditory by specifying the recommendations in DG 3 as "required", but that creates a layer of ambiguity. I specify the maximum lateral drift and under a given loading that is to occur. DG 3 uses a 10 year wind for servicability. I also specify the maximum girt and purlin deflections.

Regards,
Harold Sprague




From: "Bruce Holcomb" <bholcomb(--nospam--at)brpae.com>
Reply-To: <seaint(--nospam--at)seaint.org>
To: <seaint(--nospam--at)seaint.org>
Subject: RE: PEMB's and lateral deflection
Date: Thu, 7 Apr 2005 09:07:04 -0500

In addition to Code prescribed deflection limits, we use AISC Design
Guide 3 - Serviceability and AISC Engineering Journal, First Quarter,
1993 for serviceability limits, but neither of these is directly for
metal building systems.  The Metal Building Manufacturers Association
(MBMA) has their own manual which (if I remember correctly) has
recommended deflection and sidesway limits.  I no longer have a copy, so
I can't quote it.  But you can order one from MBMA.

Any current metal building systems designer out there who can elaborate?


Bruce D. Holcomb, PE, SE
Structural Engineer & Vice President
Butler, Rosenbury & Partners


-----Original Message-----
From: Jim Wilson [mailto:wilsonengineers(--nospam--at)yahoo.com]
Sent: Thursday, April 07, 2005 8:53 AM
To: seaint(--nospam--at)seaint.org
Subject: PEMB's and lateral deflection

Are there any official industry position statements or
articles on coordinating maximum lateral deflection of
PEMB's with rigid masonry facades?  I am looking for a
little more "oomph" to add into a letter to a future
building owner.

James Wilson, P.E.
Stroudsburg, PA

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