zero channel torsion
 

zero channel torsion
when applying a concentrated load onto a single section of channel, at what location would there be no torsion acting upon its cross section – at its shear center or the centroid? i have the flexibility in the design to place the concentrated load where there would be no torsion. any information would be appreciated. thank you.
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vava1,
place the load at the shear center to eliminate torsion.
best regards,
ba
baretired is correct. you have to locate the load at the shear center to eliminate torsion.
there is discussion of this in s&j in the chapter on torsion.
baretired is right... but remember your complete load path; next you need to consider the effects at the support. of course this would need to be done for any beam, however with a channel i often see engineers neglect the eccentricity at the support caused by the shear centre often not alligning with the centre of the support column.
channels are the only member i can think of off the top of my head which are best side (or face) connected to a support column; fasten them with the web flat against the
youngstructural-
i recently (about a month or so ago) posted a question here regarding your last post. my question was why a channel welded to a support would need to be designed for torsion, but the connecting c-chaped weld would not be. we never came to a definitive conclusion, but your last post in this thread implies that the connection should also be designed for the torsion (referred to the shear center of the section, and not the centroid of the weld group).
did i interpret your post correctly?
do you have any literature on this?
structuraleit,
ys is talking about torsion about an axis parallel to the direction of the channel. it is a small torsion, but the connection must be designed for it. a channel loaded at its shear center and simply supported on a flat surface with no connecting material would fall over on its web.
your post at:
ba-
my post was referring to torsion about the axis of the member. how can you get torsion about an axis perpendicular to a
if your post was referring to torsion about the axis of the
if i follow correctly, i believe baretired has addressed the issue. is there anything outstanding to discuss, structuraleit?
please post again if we need to chat something through... include the previous thread; i'm not sure which one you mean. i do not believe i posted at the link ba included.
these fundamentals are often the tripping stones that people (myself included) miss small portions of, which can make all the difference in the world.
cheers,
ys
b.eng (carleton)
working in new zealand, thinking of my snow covered home...
thank you everyone for your help!
vava1
my question still persists, mainly because the information in this thread is virtually completely contradictory to that in the thread i started. with the exception of 1 or 2 people, everyone who responded to my thread seemed to think that the weld should not have to take the torsion for a channel loaded through its centroid.
i am attaching two sketches which clarify exactly what i am talking about.
the first one (labeled case 1) has the channel loaded through the centroid. there is clearly torsion on this channel because it is not loaded through the shear center. that being said, do you design the weld for the direct shear (p) and the torsion (mt) or just the direct shear since the load does go through the centroid of the weld group. even if you go into the steel manual and use the icr method, you use the eccentricity as the distance of the applied load from the centroid of the weld group.
for case 2, the load is applied at the shear center of the channel so there is no torsion on the channel, but traditional connection design says to design the weld for the torsion............... so, do you or don't you?