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What size I beam should i use?

  1. Mar 4, 2013 #1
    I am designing a roof which is 5 metres wide and 10 metres long. the total weight it has to support is 20,000 kg.

    there will be two I beams spanning the 5 metre width, each i beam is 3.33m apart.

    what dimensions should i use for my i beam?

    any help would be massively appreciated, is there an industry standard beam for this type of project?
  2. jcsd
  3. Mar 4, 2013 #2
    Need more info.

    I'm not quite sure the application or if this is just a problem from your homework.

    But there is a lot that goes into structural design and we need more information about what you're setting it on and your perimeter structure. Is it sitting on masonry wall? what kind? is it going to be secured mid span to a girder? Is the roof pitched? What is the other structural information? Most likely for things like this, you would have a square steel (i-beam) frame around the perimeter and use metal joists to span the short distance at approximately 1.5m-2m on center. If its allowed by your local code, you may also wind up using wood trusses & girders. You get the joist size, by taking the length of the longest unbraced portion of the beam, its dead and live loads for the area its supporting, and the load it has to support. You have to account for wind loads, uplift forces and resistances and how much beams/joists are allowed to deflect.

    Normally, you would have to get this work permitted and have the stamped of a licensed structural engineer for it. Could you give some more information?
  4. Mar 4, 2013 #3
    Assuming this is a real project, stop what you are doing and contact a local civil/structural professional engineer. You are out of your element. Do not put people in danger due to your ignorance.

    If this is a homework problem, please state so. I think there is a different forum for that.
  5. Mar 4, 2013 #4

    /Agreed. Structural steel is not a Do It Yourself home project.
  6. Mar 4, 2013 #5


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    Staff: Mentor

    Good advice. Thread closed.
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