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Monorail Weak Axis Bending

Monorail Weak Axis Bending

Monorail Weak Axis Bending

(OP)
This might sound like a silly question, but the reference manual i'm reading confused me.

When considering side thrust and weak axis bending on a monorail I understand that you consider only one flange to contribute to weak axis bending strength.

However, in this design example i am reading, the beam is unsupported along its entire length and it appears when they check combined bending (i.e. Mfx/Mrx + Mfy/Mry =< 1.0) they assume the compression flange is braced.  Shouldn't the flange be considered unbraced (i.e  calculated Mu and determine the reduced value of Mry?

RE: Monorail Weak Axis Bending

(OP)
that first post should read

"you consider only THE flange"

RE: Monorail Weak Axis Bending

what example are you reading?  

RE: Monorail Weak Axis Bending

(OP)
Crane Supporting Steel Structures - Design Guide 2nd Edition - R.A. MacCrimmon

RE: Monorail Weak Axis Bending

If they are welded as usual the built-up section must be checked for the effect of the proper set of combinations of independent loading sets.

RE: Monorail Weak Axis Bending

Have you included bottom flange bending due to the wheels riding on the lower flange? Then use Mohr's circle to combine stresses from this primary and secondary bending.
 
A monorail beam should be designed as laterally unsupported between supports unless there are other intermendiate lateral braces present.

Recognize that the hanging load from the bottom of the beam is a "righting" load that will have a tendency to pull the beam back vertical unlike a load on the top flange which will have a tendency to push the beam over.



 

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