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Homework Help: Rectangular hollow section

  1. Jan 5, 2012 #1
    1. The problem statement, all variables and given/known data

    Dimensions: length - 400 mm, width - 125 mm height - 50 mm
    thickness - 3 mm

    included 6 holes for m12 bolts at the top, 4 holes for m6 bolts.

    will this section be able to hold a 30kg floodlight.

    2. Relevant equations

    3. The attempt at a solution

    still trying to find relevant equation for hollow section
  2. jcsd
  3. Jan 5, 2012 #2
    You question is incomplete. How is the "hollow section" being used? Cantilever, supported on both ends, ...?

    How is the rectangular section oriented? What is it attached to, and by what method? How and where is the floodlight attached? What are it's dimensions?

    For a complete answer, you will also need to know the material properties, and the fasteners' specifications.
  4. Jan 6, 2012 #3


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    Science Advisor
    Homework Helper

    Well said by pantaz. Worst case might be to assume the beam is a cantilever. Therefore, even if bending about the minor axis, the bending stress on the global cross section would then be a mere 6.44 MPa, which is very little, assuming this beam is steel or aluminum. Holes near the neutral axis tend to be negligible. Large holes near the extreme fibers might be significant, if the beam were subjected to high bending stress, which currently appears to perhaps not be the case.

    But as pantaz alludes to, the joint stresses might instead govern. Therefore, we probably need to see a dimensioned diagram of the assembly, boundary conditions, fastener material specifications, and bolt installation torque. azmo, is the given problem in post 1 a school assignment? Or not?
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