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orsion on a loose lintel supporting brick

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发表于 2009-9-16 15:13:17 | 显示全部楼层 |阅读模式
torsion on a loose lintel supporting brick
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

i can't re  
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.
note that ix+iy is the polar moment of inertia, not the torsion constant.
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.
begin on page 1-117 of the 9th edition asd or 1-89 or the 3rd edition lrfd.
ah!  gotcha...thank you
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.
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