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  • simply supported one span beam mass minimizing

    Discussion in 'The main mechanical design forum' started by jimxz, Nov 4, 2015.

    1. jimxz

      jimxz Member

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      hello there. I'm facing a problem here I need help with please.

      I have a 1000mm simply supported beam that is under two point loads at 333mm and at 667mm. each point load is 49.8 KN downwards

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      I've tried many ways to do that. but I need to know how to use (triangles) to reduce torsion and deflection and surely total mass. here are the phases I worked with and what I reached at the final image. but how do I use triangles ?

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    3. robertjeffery

      robertjeffery Active Member

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      I assume this post is dead and gone, two months later, but just for future reference.

      1 - What material are you working with
      2- you sure displacement is the correct way to determine whether the beam is strong enough. displacement is a tricky number to decide on what your limit it. unless its something like a floor joist, where you know that it will feel disconcerting with 3mm or more displacement.

      Generally we size beams and components due to the loading and the YIELD STRESS of the component.

      eg if the beams above are Aluminium extrusions. possibly a good grade 3000 series you possibly wont want to load it more then 100Mpa of stress?????

      also a note on the FEA models, a simply supported beam is very tricky to simulate in most FEA packages. as strictly speaking the components are able to slide over the knife edge, where you have mated the above images as Fixed Geometry so it turns the above beams into a tightrope walk. (a tightrope stretched between two skyscrapers will hold a 1000Kg - that same tightrope placed in simply suuported practice, wont even be able to support its own weight)


      the simplest concept for modeling simply supported beams is to cut them in half, fixed geometry the center of the beam and apply load to the supporting end (remembering to half the load) and treat them as a simply cantilevered beam. although in your instance will still take a little bit of thinking about as you are not point loading the middle of the beam.

      hope this is of some help. Cheers Rob
       

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