Lion06
Structural
- Nov 17, 2006
- 4,238
Here is the situation. I have a WF in an existing building that is being modified. The modification is going to introduce significant torsion on WF. I am going to weld the web of a channel to the flanges to create a closed section. In trying to dumb down the torsional analysis, I am only checking the closed section for torsion (assumed HSS with wall thickness = the smallest of the channel web, WF web, or WF flange) and neglecting the outstanding parts of the composite section (i.e. channel flanges, and WF flanges not connected to the channel web).
The member is fine for torsion (as would be expected).
It is my understanding that because it is a closed section the warping stresses are negligible such that there will be no addition to the bending stresses from torsion. Is that a fairly accurate statement?
If it is, would it be reasonable for me to use the WF with just the web of the channel (such that the section looks like this ___ )
_|_|
for flexure and do two seperate checks?
I would do one check for torsion using the conservatively assumed HSS section only and do a second check using the shape above for flexure. Again, my reasoning for assuming the two seperate analyses are valide is that the closed section reduced the warping normal stresses (what would add to the flexural normal stresses) to a negligible amount. I would also design the weld of the channel to the WF using Blodgett - he has a good example of the shear flow in a built up section subject to torsion.
I would really appreciate some opinions.
The member is fine for torsion (as would be expected).
It is my understanding that because it is a closed section the warping stresses are negligible such that there will be no addition to the bending stresses from torsion. Is that a fairly accurate statement?
If it is, would it be reasonable for me to use the WF with just the web of the channel (such that the section looks like this ___ )
_|_|
for flexure and do two seperate checks?
I would do one check for torsion using the conservatively assumed HSS section only and do a second check using the shape above for flexure. Again, my reasoning for assuming the two seperate analyses are valide is that the closed section reduced the warping normal stresses (what would add to the flexural normal stresses) to a negligible amount. I would also design the weld of the channel to the WF using Blodgett - he has a good example of the shear flow in a built up section subject to torsion.
I would really appreciate some opinions.
