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RE: Diaphragm

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Gerald:
Thanks. Even though Qatar is not in a seismically active area, the
height of precast walls ( thickness 1 foot ) are 57 foot. I am planning
to consider the weight of walls for the seismic load even though in the
overall structure wind load will be dominating.
I'll try to look to "TILT-UP EARTHQUAKE FAILURES" to understand more
about such aspects. 
Regards
Ashraf

-----Original Message-----
From: Gerard Madden, SE [mailto:gmadden(--nospam--at)maddengine.com] 
Sent: Sunday, May 28, 2006 8:40 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: Diaphragm

If you are not in a seismically active area, then the walls being
concrete
are not as much a concern. As you know, earthquake forces are dependant
on the mass of the structure, so concrete being dense/heavy when
compared
to a perimeter curtain wall or light framed construction (there by not
being
tied into a 2nd floor)is what I meant. A one story concrete wall in a
high
active zone can reach 0.3-0.9g very easily for the wall anchorage and
sub-diaphragm
design. With a 30 foot tall wall, those are large forces.

If you want to understand about diaphragm behavior and wall anchorage
sub-diaphragms,
I would suggest the you Google "TILT-UP EARTHQUAKE FAILURES" or
something
like that and you can see how this is the most critical aspect in one
story
concrete structural design in earthquake country.

However, if you're structure is governed by wind design, the diaphragm
still
needs to behave in the same fashion.

-gn

>-- Original Message --
>Subject: RE: Diaphragm
>Date: Sun, 28 May 2006 07:13:25 +0300
>From: "Ashraf, Mohammed (Qatar)" <mohammed.ashraf(--nospam--at)worleyparsons.com>
>To: <seaint(--nospam--at)seaint.org>
>Reply-To: <seaint(--nospam--at)seaint.org>
>
>
>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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>>
>>
>>
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