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Homework Help: Torsional checking for Steel angle member

  1. Dec 21, 2012 #1
    1. The problem statement, all variables and given/known data

    I meet a problem below:

    To check if the angle :200x150x12 S275 Grade can take a twist of 30kNm (on plan ) with Span 3m fixed end connected.

    2. Relevant equations
    θ = T L / J G

    3. The attempt at a solution
    My question is that even I got the angle of twist for this member??
    how can i check against design twist (30kNm) to see if it is adequate ???
  2. jcsd
  3. Dec 21, 2012 #2


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    Science Advisor
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    Gold Member

    Well this case should generally be avoided because angle sections are not very good in torsion. What you are looking for is the max shear stress in the member, Tc/J, where T is the twisting moment, c is the angle thickness, and J is the polar moment of inertia often calculated by summing the values of 'bt^3/3' for each leg, where b is the appropriate leg width. Then compare that stress to the allowable shear stress of the material. Note that the steel angle section will both twist and warp. I haven't done such a calculation since school days.
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