I-beam torsional stress calculation 3

[tnteng]

Can anyone tell me how to calulate torsional stress on an I-beam section? I have read texts that state that the shear stress of each individual section is based on the the sum of torsional resistances of each individual section of the beam. Is this the standard way of computing the shear stress (due to torsion) for non-circular members?

What is the torsional constant "J" as listed in the Torsion Properties table of the AISC Manual of Steel Construction. Is this value used in the stress calculation as described above?

Thanks in advance,

 

[JedClampett]

Get a publication from AISC called, "Design Guide 9: Torsional Analysis of Structural Steel Members / Seaburg and Carter (1996)" It will guide you through the calculations required to analyze I shaped sections for torsional loads.
You'll see that there are two mechanisms which create torsional capacity for I beams. The pure torsional shear capacity is what you described above. A much larger component of capacity is created by torsional warping. This is when the top and bottom flanges have equal shear loads in opposite directions. This also causes tension and compression forces in the member.
These analyses are quite complicated. You might want to get someone who's done it before to guide you through it. Try posting on the "Structural Engineering-Other Topics" board.

 

[tincan]

"Torsion Analysis of Rolled Steel Sections' by Bethlehem Steel is another good referencd.

 

[JedClampett]

tincan, you must be the same vintage as I am. I still use the Bethlehem Steel "Steel Design File for Torsional Analysis". But the reason I didn't mention it was that Bethlehem Steel is gone and I'm sure they didn't give away (yeah, they gave me my copy) or sell their publications for years. However, if you can find one, it's still a good reference (although the steel shapes have changed since my edition).

 

[tincan]

JedClampett
yeah, old school. However our library has a search service to locate older books, etc. I had them chace down sereral books by Timoshenko, Treseige, Heneiti and a couple of booklets. I like to play around with "elastic foundation".

Some libraries may have access to some of the golden oldies and share. I've had books/etc loaded to our library from all over the US. Maybe, others can use this service to find some of the out of date data. I dont feel to bad about copying 40-60 year old data.

I've been putting the "Moments and Reactions for Rectangular Plates" by the Bureau of Reclamation I found on spreadsheets, my eyesight is getting to poor to tead the fine print. That was the best 55 cents I ever spent.

Best, Tincan, BSCE'63

 

[dpa]

Lincoln Arc Welding Foundation. "Design of Welded Structures" U of Washington Book store almost always has it in stock. I'll bet most college book stores with engineering departments also have it. It is published approximately at cost as a public service. (Way cheaper than most engineering books) Probably similar to the Bethlehem books. They are no nonsense for example they dont call shear flow VQ/Ib they call it Vay/Ib so you don't have to ask yourself "What the hell is 'Q'?"

Good Luck