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    Discussion in 'The main mechanical design forum' started by NMC, Dec 6, 2018.

    1. NMC

      NMC Member

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      Hi all,

      I am having a debate with a colleague on what several structural components are and how they are described, we are differing on opinion!


      For the roof image, I believe the arrow is describing a 'Strut' component, however, could it be a tie rod or truss?

      For the bench image, I believe the arrow is describing 'pinned and pinned' however, could it be built in and free?

      Thank you.

      Roof 1.jpg bench 1.jpg
       
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    3. Exupery

      Exupery Well-Known Member

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      Okay so since the component of the building is a component of a building, I don't think you can judge from the shape. Structural components differ depending on the loadings they withstand, not the shape.
      So, if the purpose of that member is to hold the other two in place then it will be a tie. If it will only withstand axial loads, it'll be a rod. As far as I know, truss and strut are used interchangeably and the way my industry sees it, is that a strut is part of a truss.

      A Bench's material wouldn't be pinned-pinned. The foundation is fixed in the ground already and it can be assimilated to a thick short beam. No need to pin those.

      My humble thought process.
       
    4. MSHOfficial

      MSHOfficial Well-Known Member EngineeringClicks Expert

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      I agree with Exupery. Strut is a member of a truss. And strut and rods both carry only compression or tension loads. They do not carry bending. Columns on the other hand carry all three. In this care I would say the whole structure looks like a truss and therefore the member you have pointed at, would be a strut.

      In reality ofcourse they carry slight bending and slight torsion too (looking at the structure) but for calculation purposes and for simplicity we can assume they only carry compression/tension.

      For the bench if we were to calculate the loads for buckling/crippling, we would consider the boundary conditions to be fixed-fixed, but that depends on if and how deep the leg is buried underground. For the length of the rod I would say for the fixed-fixed condition to be taken, we would want atleast half the length of the rob above earth, to be buried under.

      Also beams like these would easily take more compression load than they would take buckling therefore buckling boundary conditions are the most important ones to consider here. That’s why I am only talking about buckling boundary conditions.
       
    5. NMC

      NMC Member

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      Thanks for your feedback.
       
    6. NMC

      NMC Member

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      Thanks for your feedback.
       

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