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RE: Drift Limits for Wind

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Be careful to differentiate between drift and deflection. There are no required "drift" limits. There are some guidelines predicated on servicability in the AISC in the AISC Design Guide 3 "Serviceability of Low Rise Buildings". And there are several guides for high rise buildings predicated on occupant comfort.

Regards,
Harold Sprague





From: "Gerard Madden, SE" <gmadden(--nospam--at)maddengine.com>
Reply-To: <seaint(--nospam--at)seaint.org>
To: <seaint(--nospam--at)seaint.org>
Subject: RE: Drift Limits for Wind
Date: Thu, 22 Sep 2005 13:09:50 -0700

Thanks to all and especially Violeta for giving a code reference (even
though IBC isn't the law of the land out here yet).

-gm

-----Original Message-----
From: Violeta Tihova [mailto:vtihova(--nospam--at)earthlink.net]
Sent: Thursday, September 22, 2005 11:45 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Drift Limits for Wind

IBC Table 1604.3 limits the deflection of exterior walls with brittle
finishes to l/240 for wind and seismic loads. Note that for cantilever
columns, l shall be twice the column length.

Violeta Tihova, P.E.
Silver State Code Consulting
1785 E. Sahara Ave. Ste. 157
Las Vegas, NV 89104
Ph: (702) 866-2633
F: (702) 893-2463


----- Original Message -----
From: "Scott Maxwell" <smaxwell(--nospam--at)engin.umich.edu>
To: <seaint(--nospam--at)seaint.org>
Sent: Wednesday, September 21, 2005 7:18 PM
Subject: Re: Drift Limits for Wind


> To elaborate on Paul's response, I would agree that "yes", you can
design
> to "to meet L/240 for wind and the Delta_M for seismic".   You can
design
> to what ever wind drift limit you want (at least as far as the code is
> concerned as I don't believe that there is any drift limits specified
in
> the code for wind).  Now, will you be "OK"?  Dunno.  Depends on what
the
> over all system (i.e. structural and non-structural items) can handle
> before problems occur.  As another poster suggested, to much drift
could
> cause problems in your stucco finish (i.e. cracking, deteriorating,
etc).
>
> But, the point is that the only CODE require drift limit is for
seismic
> (that I am aware of).  Of course, "standard of care" might dictate
some
> wind drift limits, but "standard of care" can be harder to interpret
than
> code requirements.  ;-)
>
> Scott
> Adrian, MI
>
>
> On Wed, 21 Sep 2005, Paul Feather wrote:
>
> > Yes, unless the finishes require something more stringent than
l/240.
> >
> >
> > Paul Feather PE, SE
> > www.SE-Solutions.net
> > pfeather(--nospam--at)SE-Solutions.net
> >   ----- Original Message -----
> >   From: Gerard Madden, SE
> >   To: seaint(--nospam--at)seaint.org
> >   Sent: Wednesday, September 21, 2005 4:13 PM
> >   Subject: Drift Limits for Wind
> >
> >
> >   I must be getting old cause I can't seem to find this, so I ask
all of
you to refresh my memory..
> >
> >
> >
> >   I have a simple storefront renovation project and I am using
cantilevered steel columns to resist the lateral wind load. The wind
force
governs over seismic by a factor of 2.
> >
> >
> >
> >   In UBC/CBC the Delta_M drift limit is 0.7*R*Delta_S .. Now that I
know
for sure is for seismic and is straight forward.
> >
> >
> >
> >   Since I have twice the load governed by wind, do I still need to
meet
this requirement?
> >
> >
> >
> >   I know technically there is no drift limit for 1 story steel
construction and this is basically a false tower/covered entrance
outside of
an existing building but I'd still like to meet the drift limit since
there
are several illuminated signage type things and stucco finish that I'd
rather not have bust all up under huge deflections.
> >
> >
> >
> >   Can I design it to meet L/240 for wind and the Delta_M for seismic
and
be okay?
> >
> >
> >
> >   TIA,
> >
> >
> >
> >   -gm
> >
>
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