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Load of a Ladder

  1. Jul 30, 2014 #1
    I am determining the max load a steel ladder can hold when placed on a 65 degree angle.
    the ladder is 12 ft long and is made out of HSS 1x1x1/8in square steel tubing.

    my idea was to treat it as a simple beam with a single concentrated load at the center "P". then once that was determined, to apply it to a triangle with "P" being the opposite side. id then solve for the hypotenuse which would be the max load straight down when the ladder was placed at the 65 degree angle.


    Was i correct in going about it in this way or is there a better way to do it? Thanks in advance!
     
  2. jcsd
  3. Jul 30, 2014 #2

    berkeman

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    This doesn't sound good. You are asking for advice on an anonymous web forum to help you maximally load a ladder that people will be using? What if you get bad advice? What is your ME background, and what professional engineer certifications do you hold? What is your insurance situation to cover you if/when somebody gets hurt using something that you designed and built?
     
  4. Jul 30, 2014 #3

    nvn

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    blake92: Your approach described in post 1 sounds correct for the transverse (bending) load. And there is also a longitudinal, compressive load (from the ladder midspan to the ground), which might need to be taken into account. Is this a schoolwork question?
     
    Last edited: Jul 30, 2014
  5. Jul 31, 2014 #4
    The ladders already exsist and have been used for years. i was just asked to see what they can hold. So we know they can hold what they are needed for but i wanted to find out what the max they can hold.

    like i said, the ladders are real. i was just asked to determine what they can hold.
     
  6. Jul 31, 2014 #5
    I don't think your analysis method is exhaustive enough. If you have access to modeling software such as SolidWorks you can use the stress analysis software and find where the max stresses will be. Once you know this, you can work on finding a worst case scenario but please, be generous with your factors of safety, an old ladder made of square tubing to be maximally loaded sounds like a disaster waiting to happened.
     
  7. Aug 1, 2014 #6
    I don't think this is a good idea at all. It may well fail at the joints, such as where the rungs connect to the side rails. These are being ignored if you treat it as a single beam. You really need to analyse the joints and the rung holding the load too, possibly with finite element analysis.

    The load will also be increased by dropping it onto the rung as the person puts his foot down. There'll be quite a difference between dropping a metal object directly onto the ladder compared to cushioning it with the muscles and shoe soles of a person.
     
  8. Aug 1, 2014 #7

    berkeman

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    Sorry, for safety reasons, this thread is closed.
     
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