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Re: X-braces

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This topic has been the topic of several search.  Try doing a search on and you will see several papers on it (accesible only for members).

1.  Design of Diagonal Cross bracings by A.Picard and D. Beaulieu:  By
theory and experiment concluded that "the effective length of the
compression diagonal is 0.5 times the diagonal lenght when the diagonals are
continuous and attached at the intersection point"

2. FEMA 356 sec. says that the effective length of each brace
shall be taken as 0.5times the total lenght of the brace including gueest
plates for both axes of buckling".

Hope this helps.

-  Aswin
Aswin Rangaswamy, P.E.
Jacobs Facilities Inc. ( )
Cypress, California

----- Original Message -----
From: "Jason Kilgore" <jkilgore(--nospam--at)>
To: <seaint(--nospam--at)>
Sent: Tuesday, November 18, 2003 1:06 PM
Subject: X-braces

> This something that I thought I knew, but a computer program is calling me
> liar.
> I have a single story building with steel concentrically braced frames.
> It's in a low seismic area and I'm using R=3.0, so AISC seismic rules do
> apply.  Standard slotted HSS X-brace, centered on work points at top and
> bottom .
> Here's my question:  Does the tension member serve to laterally brace the
> compression member?  It obviously does in the plane of the braced bay.  My
> argument is that since the opposite member is in tension, it doesn't allow
> the compression member into out-of-plane first order buckling along its
> length.  Instead, the compression brace is forced into second-order
> with the center of the "X" as the node.
> Any comments?
> ----
> Jason W. Kilgore
> Project Engineer
> Leigh & O'Kane, L.L.C.
> Kansas City, Missouri

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