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RE: Drift Limits for Wind

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Yes, thanks Violetta for setting me straight.  Darn code buggers...always
slipping something new in.  <grin>  Keeps an engineer on one's toes!

Scott
Adrian, MI


On Thu, 22 Sep 2005, Gerard Madden, SE wrote:

> 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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