Monday, October 13, 2008

RE: Is it a Braced Frame or Cantilevered Column?

Good Lord, I hope not!  Actually, I have been thinking about it since I posted the question.  Tell me if I'm crazy (some have in the past), but, if you have a horizontal member at the 4ft elevation and that is where the lower end of the braces are located at the intersection of that horizontal and the columns (note the columns are only about 7ft apart and about 15 ft high), then the moment diagram for the column should be "shaped" similar to a rigid frame, with the difference the "beam" at the top of the frame is very deep (height of the columns less 4ft).  Therefore I think you could design with an R=3.25, due to the "braced frame" portion of the frame rather than having to use an R=1.25 for a cantilevered column system.

 

Yes, no, maybe?

 

Joe

 

Joseph R. Grill, PE

 

 

 

From: Tom.Hunt@fluor.com [mailto:Tom.Hunt@fluor.com]
Sent: Monday, October 13, 2008 2:09 PM
To: seaint@seaint.org
Subject: Re: Is it a Braced Frame or Cantilevered Column?

 


Joe,

Not that I would wish this on anyone, but could this be an Eccentric Braced Frame?!

Thomas Hunt, S.E.
Fluor


"Joseph R. Grill" <jrgrill@cableone.net>
10/13/2008 12:41 PM
Please respond to seaint

To

<seaint@seaint.org>

cc

Subject

Is it a Braced Frame or Cantilevered Column?

 




I have a braced frame (residential design) location in a SDC D.  Dead load weights for the structure will allow me to use an ordinary braced frame.  However due to architectural considerations (a hearth opening where the frame is hidden within a framed fireplace) I am trying to raise the lower connection of the braces above the elevation of the hearth opening.  I'm not sure if it can still be considered a braced frame (for R values) of if it should be considered a cantilevered column even though it really isn't cantilevered (no fixed base for moments).
 
Or is it something all together.  Of course I would rather consider it an ordinary braced frame rather than cantilevered as the lateral loads are much less.  
 
Thanks again.
Joe
 
Joseph R. Grill, PE 

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