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Re: Diaphragm

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If the roof diaphragm is at "different levels" you need to resist the
wind loads at each location where the roof changes levels.

Stan Scholl, P.E.
Laguna Beach, CA

On Sun, 28 May 2006 07:13:25 +0300 "Ashraf, Mohammed \(Qatar\)"
<mohammed.ashraf(--nospam--at)worleyparsons.com> writes:
> Thanks for all for your help.
> Gerald:
> I've precast concrete walls all around and building is almost one 
> storey
> but at different levels and I would like to know why you have
> specifically asked about the perimeter wall system?
> Qatar is not considered as seismically active and wind loads are
> dominating.
> The seismic loads we are taking is just 0.01W as per client 
> documents. 
> I am not familiar with sub diaphragm and could you further explain 
> about
> that. 
> The client document says we've to use standing seam metal roof such 
> as
> Bemo.
> That's the reason why we are using standing seam metal roof.
> Regards
> Ashraf
> 
> -----Original Message-----
> From: Gerard Madden, SE [mailto:gmadden(--nospam--at)maddengine.com] 
> Sent: Sunday, May 28, 2006 3:10 AM
> To: seaint(--nospam--at)seaint.org
> Subject: RE: Diaphragm
> 
> There is nothing wrong with a flexible diaphragm. You just need to 
> make
> sure the load can get there and you are accounting for this 
> behavior
> (load
> based on tributary or simple beam analogy).
> 
> Like others have said, you can use horizontal braces to stiffen it 
> up
> too
> but if your metal deck is like Verco or something and not Standing 
> seam
> metal roofing, then you may not need to do this.
> 
> Does the building have mostly concrete perimeter walls? Is it one 
> story?
> If yes to both, your primary problem will be wall anchorage and
> sub-diaphragm
> system (I'm assuming Qatar is at least moderately seismically 
> active).
> 
> -gm
> 
> >-- Original Message --
> >Subject: RE: Diaphragm
> >Date: Sat, 27 May 2006 10:01:53 +0300
> >From: "Ashraf, Mohammed (Qatar)" 
> <mohammed.ashraf(--nospam--at)worleyparsons.com>
> >To: <seaint(--nospam--at)seaint.org>
> >Cc: <seaint-ad(--nospam--at)seaint.org>
> >Reply-To: <seaint(--nospam--at)seaint.org>
> >
> >
> >Thanks GM. I am using IBC 2003 code.
> >A brief description of building is given below for your info.
> >The building is of 107x60 m in plan size and maximum 17m height 
> with
> >roofs at different levels.
> >The columns are of concrete and most of the beams are of steel. 
> Roof is
> >of steel deck type. I have about 7 braced frame in the x-direction
> (107m
> >is in x-direction). The span of frames vary from 10 to 22m. In the
> >y-direction there are 7 columns @ a spacing of 10m. Only 3 bays 
> are
> >braced. The height of braced bay is 8m and span is 10m.
> >The maximum size of diaphragm comes around 60x22m. 
> >What can I do to make this system more rigid?. Since I am using 
> Open
> Web
> >Joists to support metal deck, does bridging help me to make the 
> system
> >more rigid?.
> >Thanks and regards
> >Ashraf
> >
> >-----Original Message-----
> >From: Gerard Madden, SE [mailto:gmadden(--nospam--at)maddengine.com] 
> >Sent: Saturday, May 27, 2006 9:43 AM
> >To: seaint(--nospam--at)seaint.org
> >Subject: RE: Diaphragm
> >
> >Most likely not. I'm assuming the walls are concrete or steel 
> braced
> >frame.
> >Unless the metal deck has concrete fill, it will be considered 
> flexible
> >diaphragm. See the UBC/IBC for the definition of Rigid Diaphragms 
> and
> >Flexible
> >Diaphragms. The deflection of the diaphragm would need to be less 
> 2.5
> >times
> >the deflection of the vertical resisting elements of the lateral 
> system
> >to consider it rigid and at best your would have a partially rigid
> >diaphragm
> >but with those plan dimensions, you would need several interior 
> lines
> of
> >lateral resistance and you must also be careful to make sure that 
> your
> >diaphragm
> >span ratios are not too great to violate whatever code your 
> structure
> >falls
> >under.
> >
> >-gm
> > 
> >>-- Original Message --
> >>Subject: Diaphragm
> >>Date: Sat, 27 May 2006 09:14:22 +0300
> >>From: "Ashraf, Mohammed (Qatar)" 
> <mohammed.ashraf(--nospam--at)worleyparsons.com>
> >>To: <seaint-ad(--nospam--at)seaint.org>
> >>Cc: <seaint(--nospam--at)seaint.org>
> >>Reply-To: <seaint(--nospam--at)seaint.org>
> >>
> >>
> >>
> >>"This email is to be read subject to the disclaimer at the end of 
> this
> >message
> >>or attached to this message."
> >>
> >>Hello all,
> >>
> >>I have building of 107mx60m in plan size and maximum height of 
> 17m.
> >>
> >>The roof is of seamless metal deck from Bemo USA or other 
> manufacture.
> >>
> >>The metal deck is supported by open web joists. The maximum span 
> of
> >>joists is 22m.
> >>
> >>Can I take this deck as rigid diaphtragm?.
> >>
> >>Thanks in advance,
> >>
> >>Ashraf
> >>
> >>
> >>
> >>
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