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RE: Diaphragm

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Daryl:
The client documents say 10 foot spacing and we are using standing seam
metal roof.
Thanks for the feedback. I'll look to this matter.
Regards
Ashraf 

-----Original Message-----
From: Daryl Richardson [mailto:h.d.richardson(--nospam--at)shaw.ca] 
Sent: Monday, May 29, 2006 5:03 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Diaphragm

Ashraf,

        Ten feet seems a rather long spacing between joists.  Will your 
metal deck span ten feet and carry the required live load?  I usually
find 
six feet, to seven-and-one-half feet, the maximum practical span for
metal 
decking; but perhaps our required live load (1 kPa, or 21 psf) is larger

than yours.  Or perhaps I missed something in an earlier post that
indicated 
some other decking material.

Regards,

H. Daryl Richardson

----- Original Message ----- 
From: "Ashraf, Mohammed (Qatar)" <mohammed.ashraf(--nospam--at)worleyparsons.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Monday, May 29, 2006 6:51 AM
Subject: RE: Diaphragm


Gary:
I've joists spaced at 10 foot and span of joists is about 74 foot.
Joists are supported on steel girders and girders are supported on
concrete columns spaced at 30 foot spacing. Hence I think flat bar
spacing will be a better choice. What do you say?. Is this called as
bridging?.
Thanks and regards
Ashraf


-----Original Message-----
From: Gary L. Hodgson and Assoc. [mailto:ghodgson(--nospam--at)bellnet.ca]
Sent: Monday, May 29, 2006 3:05 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Diaphragm

Ashraf,
You can install X-bracing angles under the steel joists from col to
column; or you can install flat bar bracing on top of
the joists, under the deck.  This pretty well has to be field welded and

needs to be pulled tight--details to work out
with the erector. The angle braces are usually bolted with connection
plates at the columns.  Count on some of the
angles not being correct and they will need to be field-welded--this
depends on the quality of the fabricator and his
detailer.
Gary

Ashraf, Mohammed (Qatar) wrote:
> 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
>>>
>>>
>>>
>>>
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