Torsion Distribution from the beam to the plan brace

[allimuthug]

Hi,

I have a pipe rack of length 10m x width 5.7m x height 2.5m. It has plan brace as well as horizontal bracing as shown in the picture attached. The columns and the vertical brace are of HE 300B and HE 180A. The Pipe Rack supports a pipe which is anchored to the transverse beam(HE400A). The Anchor support of pipe is 1.5m away from the Plan brace connection.
Since the Load is applied to top flange it is transferred to the transverse beam as torsion and minor axis bending, but the question is weather the Plan brace will resist torsion since it is connected 120mm below the top flange. Also please explain in detail for the torsional distribution if the plan brace resist torsion.
[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1537765958/tips/Torsion_Distribution_izjwre.pdf[/url]

 

[Agent666]

The brace is going to try take some moment from the torsion depending on the combined bending stiffness of the connecting plate and brace member, and the effect of the magnitude of the torsion and resulting twist.

If a really stiff plate is used then web and plate will obviously have to accommodate the resulting twist and will end up with more of the torsion being transferred as moment than if a thinner more flexible plate was used. If torsion is high, then plate or web may even yield. If its a really thin plate, it may just deform elastically.

Your plan brace may not be doing too much to actually restrain the section as a brace point for lateral torsional buckling as it's not located at or connected to the critical compression flange. Similarly it might not be doing to much for other lateral loads acting horizontally at top flange level (maybe walkways, other live loads etc), how does the force get down to the brace for example as this in itself creates a torsion on the brace connection (load acting at top flange at an eccentricity). You might want to consider these effects in your final detailing.

 

[Agent666]

Just thinking aloud, why not coincide the bracing node location with the pipe location and forget about putting the member into torsion?

 

[WARose]

Since the Load is applied to top flange it is transferred to the transverse beam as torsion and minor axis bending, but the question is weather the Plan brace will resist torsion since it is connected 120mm below the top flange.

As close as the gusset is to the neutral axis, I doubt very much torsion would try to transfer. You'd also have to consider the out-of-plane flexural stiffness of your web.....which is pretty minimal.