torsion on a loose lintel supporting brick

[hippo11]

I am trying to check the torsion of a loose lintel vs the BIA-recommended limit of 1/16"....but I can't find the "J" of steel angle shapes for my T*rho/J formula. Does anyone know where I can find J of angles? Can I just take J=Ixx+Iyy?

thanks

 

[Lion06]

I can't remember the exact limitations of using J=Ix + Iy, but I don't think that holds true for open sections.

 

[UcfSE]

The AISC manual has a table of torsional properties for hot-rolled shapes. See part 1 of the third edition LRFD, part 1 of the ninth edition ASD, or AISC design guide 9. If you are outside of the US, you'll have to check your own references and manuals, but it shouldn't be a mystery.

 

[UcfSE]

Note that I_x+I_y is the polar moment of inertia, not the torsion constant.

 

[hippo11]

I didn't see J in part 1 of 2nd ed'n or 3rd ed'n of LRFD or J in ASD...J's not in there.

 

[UcfSE]

Begin on page 1-117 of the 9th edition ASD or 1-89 or the 3rd edition LRFD.

 

[hippo11]

ah! gotcha...thank you

 

[WillisV]

For open sections (such as angles), the torsional constant J is equal to (1/3)*the sum of b*t^3 of all the pieces.