Kink Brace Out-of-Plane Buckling Stability

[swearingen]

For a kinked brace, the out-of-plane buckling stiffness is obviously less than if the member is straight. My question is: how much less?

Intuitively, it seems that it is even less than the KL/r using the length of the two segments added together. You are losing strong axis buckling resistance in the brace at the kink - but again, how much? I would think this stiffness would reduce rapidly as the angle of the kink grew.

Please see the attached sketch for a visual. Note that the brace is kinked to begin with (to clear mechanical equipment), not due to the load.

Any guidance would be appreciated...


-5^2 = -25 ;-)

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[JAE]

Is there a moment-connection across the intersection at the kink in the out-of-plane direction?

 

[a2mfk]

I think I would treat the three diagonal members labeled "C" as individual members, like chord and web members of a scissor truss. The upper right corner "C" is like a vertical web in a truss, and because of the skew/kink there will be compression in this member.

Like JAE I am wondering if there is out-of-plane bracing at that intersection. Without it, my idea may not work.

 

[swearingen]

JAE - yes, the main member (shown from top left to bottom right in my sketch) has a fully welded, mitered joint, as if the beam/brace just made a slight turn. The 3rd member is just to take the in-plane offset thrust introduced by the kink.

a2mfk - Yes, the upper right member will take compression - that's what it's there for. No, there is no out-of-plane bracing which is why the member is rotated so that the strong axis faces that way.

PS: The "C" on each member was just indicating that they are all in compression - understandably elementary for this forum.


-5^2 = -25 ;-)

http://www.eng-tips.com/supportus.cfm