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RE: Diaphragm

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Gary,
Thanks. You are right and I am not comfortable with the diaphragm action
of metal roofs. I am planning to use open web joists to support the
standing seam metal roof as shown in the client documents. But if I want
to put X-bracings in the roof, how can I provide it?.
Regards
Ashraf
-----Original Message-----
From: Gary L. Hodgson and Assoc. [mailto:ghodgson(--nospam--at)bellnet.ca] 
Sent: Monday, May 29, 2006 2:39 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Diaphragm

Ashraf,
For a building that size, I would put in X-bracing in the roof.  The 
CISC has stated that for large buildings,
diaphragm action is not reliable.  However some eminent engineer 
(Galambos?) has disagreed with that.
Gary

Ashraf, Mohammed (Qatar) wrote:
> 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
>>
>>
>>
>>
>> *** WORLEYPARSONS GROUP NOTICE ***
>> "This email is confidential.  If you are not the intended recipient,
>> you must not disclose  or  use the  information  contained in it. If
>> you have received this email in error,  please notify us immediately
>> by return email and delete the email and any attachments. Any
personal
>> views/ opinions expressed by the writer may not necessarily reflect
>>
>> the views/ opinions of the company."
>>     
>
>
>
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