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Re: cold formed braced frame

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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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