Torsional Constant "J" Composite Section
Torsional Constant "J" Composite Section
(OP)
I am analyzing lateral torsional buckling per AISC of a WF shape reinforced with angles. Would the Torsional Constant "J" of a composite section simply be the sum of J of the individual members?
In review of AISC DG9 it appears J for an open section can be calculated as the sum of bt^3/3 which would make me believe the torsional constant would be additive and the composite "J" is not dependent on the spatial relationship of the members in the composite shape?
In review of AISC DG9 it appears J for an open section can be calculated as the sum of bt^3/3 which would make me believe the torsional constant would be additive and the composite "J" is not dependent on the spatial relationship of the members in the composite shape?






RE: Torsional Constant "J" Composite Section
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: Torsional Constant "J" Composite Section
RE: Torsional Constant "J" Composite Section
RE: Torsional Constant "J" Composite Section
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: Torsional Constant "J" Composite Section
RE: Torsional Constant "J" Composite Section
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: Torsional Constant "J" Composite Section
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: Torsional Constant "J" Composite Section
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: Torsional Constant "J" Composite Section
I used a W30x191 as my wide flange with L6x6x1/2 angles connected in the same manner shown in KootK's picture.
RE: Torsional Constant "J" Composite Section
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: Torsional Constant "J" Composite Section
RE: Torsional Constant "J" Composite Section
I ran it by hand as a pair of HSS 6x12x1/2, ignoring the thickness difference in the flange. Came to 820 in^4 which is within about 5%.
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: Torsional Constant "J" Composite Section
RE: Torsional Constant "J" Composite Section
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: Torsional Constant "J" Composite Section
RE: Torsional Constant "J" Composite Section
The judicious application of code LTB provisions is appropriate in my opinion.
This is true for shear but less so for torsion (and therefore LTB).
J we've discussed. Iy should be pretty easy. Radius of gyration is manageable as SQRT(I/A) of the compression zone. Cw is a bit trickier. One approximate approach would be to calculate Cw assuming fictional beam flanges having the same Iy as the composite flange/reinforcing angle assembly. Lastly, be conservative with your residual stress assumptions and remember to account for loads locked into the system prior to reinforcement.
Not sure what you're asking here. LTB bracing would need to satisfy the usual AISC provisions. Given that you're looking at a column, however, I would expect that you only have LTB bracing at the top and bottom of the column.
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.