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Single angle allowable bending stress based on ASD method

Single angle allowable bending stress based on ASD method

Single angle allowable bending stress based on ASD method

(OP)

I tried to attach a pic of the problem it didnt accept ???

However it is an equal leg angle vertical leg toes up
Load is applied on tip of cantelever
Load is due to attachment of girt to horizontal leg by two bolts

I dont know if that triger a biaxial bending? Torsion ? And how to design it based on ASD 9 edition?

Thank you for ur help




RE: Single angle allowable bending stress based on ASD method

Any reason you're looking to use a specification that's almost 30 years old?

Without the picture it's hard to tell but it sounds like it's predominantly going to be simple flexure without much biaxial bending or torsion. That picture would definitely help. Look in section F9 of the specification of 14th edition AISC manual.

Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries
www.americanconcrete.com

RE: Single angle allowable bending stress based on ASD method

Quote (Ted)

Any reason you're looking to use a specification that's almost 30 years old?
Wow, is it that old? I should probably upgrade.

RE: Single angle allowable bending stress based on ASD method

You'll need to use your judgment based on your conditions but I suspect that the flexural stiffness of your girt will probably rectify the load delivery such that torsion can be neglected. That will leave you with geometric axis bending in the vertical plane and then, by way of the usual single angle voodoo, some additional bending in the horizontal plane.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Single angle allowable bending stress based on ASD method

Whoops, I posted the wrong section; F9 is for double angles and tees, F10 is for single angles and their associated "voodoo".

Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries
www.americanconcrete.com

RE: Single angle allowable bending stress based on ASD method

Attached is the results of a FEA as I understand your situation. As you can see, assuming that the girt does not provide any torsional restraint to the angle it would twist. In other words, this is just a cantilevered angle with a weight hanging off the end. Just so you know I modeled a L3x3x1/4 that is 36" long with a total of 200 lbs. at the end. The ASD 9th ed. code offers no guidance that I can find on how to design an angle like this. You mentioned biaxial bending, so don't forget the geometric axes (axes parallel to the legs) and principal axes are not the same so really by definition this problem does have biaxial bending, i.e., bending about the major and minor axis.

I agree with the previous comments, you should use the latest edition of AISC to design this. With their lack of symmetry and sensitivity to where you load them, angles are tricky things. Just dividing the moment by the section modulus and checking that that is less than the yield strength divided by a factor of safety doesn't get it.

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