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Re: cold formed braced frame

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I hear you. I am dealing with a structure that has been manufactured and
delivered prior to permit issuance and prior to my involvement. I was
retained to clean up the mess and am trying to get the structure to comply.
This is the price one pays for living in an agricultural community but hey,
no traffic, good schools etc...

It is a light, light, light greenhouse structure. Roof dead load of 1.2 psf.
The k-braced frames are taking 729# pre omega.

2213.8.5 provides the exception to 2213.8.4.2 and also specifies designing
braces for omega.

Thanks again for your input, it has been valuable and is greatly
appreciated.

Regards,

Mark

----- Original Message -----
From: <Rick.Drake(--nospam--at)Fluor.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Thursday, May 31, 2001 3:37 PM
Subject: Re: cold formed braced frame


>
> I wouldn't use a K-braced frame under any circumstances in Seismic Zones 3
> or 4.  See UBC Section 2213.8.4.2.  The concern is brace buckling leading
> to column buckling leading to collapse.
>
> Rick Drake, SE
> Fluor Daniel, Aliso Viejo, CA
>
> ****************************
>
>
>
>
>                     "Mark Baker"
>                     <shake4bake@eart      To:     <seaint(--nospam--at)seaint.org>
>                     hlink.net>
>                     05/31/01 01:59        cc:
>                     PM
>                     Please respond        Subject:     Re: cold formed
braced frame
>                     to seaint

>
.
>
>
>
>
>
> In other words, applying omega established for hot rolled sections would
> still be mixing apples and oranges....
>
> I'll let you know what bumping up my seismic forces by 2.2 results in. I
> think I'll be o.k. but won't know for sure until I run the numbers.
>
> Am I leaping to far to say you would not apply omega level force to a
> k-braced frame of light gauge material?
>
> Mark
>
> ----- Original Message -----
> From: <Rick.Drake(--nospam--at)Fluor.com>
> To: <seaint(--nospam--at)seaint.org>
> Cc: <seaint(--nospam--at)seaint.org>
> Sent: Thursday, May 31, 2001 12:14 PM
> Subject: Re: cold formed braced frame
>
>
> >
> > Mark:
> >
> > A few additional thoughts before you go much further.
> >
> > Omega is a measure of the "pushover strength" of the structure as a
> whole.
> > In other words, how much load can it take beyond the prescribed base
> shear
> > force. I would expect that omega values for cold-formed steel to be very
> > low, nowhere near those assigned to structural steel structures.
> >
> > Regards,
> >
> > Rick Drake, SE
> > Fluor Daniel, Aliso Viejo, CA
> >
> > *****************************
> >
> >
> >
> >
> >                     "Mark Baker"
> >                     <shake4bake@eart      To:     <seaint(--nospam--at)seaint.org>
> >                     hlink.net>
> >                     05/31/01 09:56        cc:
> >                     AM
> >                     Please respond        Subject:     Re: cold formed
> braced frame
> >                     to seaint
> >
> .
> >
> >
> >
> >
> >
> > Thank you Rick, you have confirmed my reluctance to try applying special
> > seismic provisions of chapter 22 to this structure.
> >
> > There seems to be no connection between any special seismic provisions
> and
> > the AISI specification for this type of structure. Section 2220 really
is
> > not applicable to this structure since 2220 deals with steel stud wall
> > systems.
> >
> > The best thing I can see to do is apply omega to all member and
> connection
> > design.
> >
> > Thanks again,
> >
> > Mark
> >
> > ----- Original Message -----
> > From: <Rick.Drake(--nospam--at)Fluor.com>
> > To: <seaint(--nospam--at)seaint.org>
> > Sent: Wednesday, May 30, 2001 4:50 PM
> > Subject: Re: cold formed braced frame
> >
> >
> >
> > Section 2213. 8 is part of Chapter 22, Division V, the seismic
provisions
> > for Structural Steel designed in accordance with the AISC ASD Manual.
> Both
> > the ASD Manual and this Division are not applicable for Cold-Formed
> Steel.
> >
> > Try UBC Chapter 22, Divisions VI, VII, and VIII for Cold-Formed Steel
> > requirements.  Section 2220 should be of great interest
> >
> > Rick Drake, SE
> > Fluor Daniel, Aliso Viejo, CA
> >
> > ********************************
> >
> >
> >
> >
> >                     "Mark Baker"
> >                     <shake4bake@eart      To:     <seaint(--nospam--at)seaint.org>
> >                     hlink.net>
> >                     05/30/01 11:58        cc:
> >                     AM
> >                     Please respond        Subject:     cold formed
braced
> > frame
> >                     to seaint
> >
> > .
> >
> >
> >
> >
> >
> >
> > any thoughts on the following:
> >
> > Greenhouse structure.
> > Framing of light gauge, cold formed  material.
> > K-braced frames and x-braced frames taking  lateral.
> > Zone4
> >
> > How can I comply with UBC 2213.8 seismic provisions  which were not
> > intended for light gau. members?
> >
> > Won't I be mixing oranges and apples when  trying to apply adjustment
> > factors to allowable axial stress which incorporate  Cc and Kl/r as in
> > 2213.8.2.2.
> >
> > Section 2213.8.2.5 limits D/t ratio to 1300/Fy  which is far different
> than
> > the limt of .441E/Fy of AISI Spec. for Cold Formed  Steel Struct.
> Members.
> >
> > I am inclined to design using AISI spec. for  allowable stresses and
> apply
> > omega to all connections and  members.
> >
> > Any thoughts?
> >
> > Thanks,
> > Mark
> >
> >
> >
> >
> >
> >
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