Would you consider the channel

[TEDstruc]

Would you consider the channel at midspan of the attached angle beam to laterally brace the angle?

My initial thought was "No", because the vertical leg of the angle is in compression and the channel is welded to the horizontal tension leg of the angle. On the other hand, I do think channel prevents torsional warping of the angle.

I've already checked the frame assuming no lateral bracing at midspan of the angle. But was curious what others thought.

 

[KootK]

- I'd consider the channel effective bracing for whole section lateral torsional buckling.

- As a separate check, the vertical angle web still needs to not buckle under flexural compression stresses (b/t checks).

 

[Agent666]

To qualify as a twist restraint, the test is whether or not the channel and its connection effectively prevents twist of the cross section. If the connection is up for transferring the notional brace forces, typically 2.5% (but can vary depending on code) of the axial compression force in the angle due to bending, acting at some eccentricity to determine the moment to be resisted than I don't see why it wouldn't brace the angle like KootK noted.

I've always tried to avoid heavy reliance on bending in angles, the lack of symmetry and principle axes not agreeing with the the legs axes makes for some interesting effects and out of plane behaviour that just make it all too hard for something so simple as shown. Bending in angles is not well addressed by my own local code (at least), but might not be true of other codes.

I've always found using a small channel section to be better bang for the buck when considering the bending capacity and stiffness for deflections than using angles to support anything substantial.

 

[southard2]

I tend to be pretty conservative. But I would not consider the compression zone of the tip of the angle to be laterally braced by the channel below. But you could add a piece of steel (a clip angle maybe) that could be welded to the top tip of the angle and then to the channel where the angle is bearing on the channel. Then I think you could consider the angle to be laterally braced on both the top and bottom sides of the angle. I also think in this instance you could say that it was braced about the z-axis as well.

John Southard, M.S., P.E.

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