1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Will truss linkages diminish vibrations?

  1. Feb 26, 2014 #1
    Is it possible to have a body supported by truss linkages and isolate them from any stresses and impulses?

    Say, we are supporting a platform on the top of a set of rigid, pin jointed and cross-linked members. If small impulses act on the bottom on the linkages(upwards), is there any possibility that the impulse does not reach the platform on the top?? Or will there be a significant reduction in its magnitude?
  2. jcsd
  3. Feb 26, 2014 #2


    User Avatar
    Gold Member

    Difficult to see why, unless you factor in real world effects such as slippage and flex between the truss joints.
    If the assembly is 'rigid', impulses will be faithfully transmitted. So there must be loss elements in the truss if the impulse is to be attenuated. These can be elastic mountings, hydraulic bumpers or whatever, but their role is to absorb the impulse before it impacts the platform.
  4. Feb 26, 2014 #3


    User Avatar
    Science Advisor

    Analyse the structure as a transmission line network.
    Design a structure that sounds dead and does not ring like a bell when hit.
    You can reduce the impulse amplitude in a number of ways.
    1. Have many different path lengths to spread the pulse in time.
    2. Use knee joints = 90° bent members to prevent axial P wave propagation.
    3. Load with lumped mass near the middle of truss members to reflect impulse energy.
    4. Use a plastic sleeve on the pins in the joints. Acoustic mismatch reflects energy.
    5. Mix your materials, bamboo, wood or aluminium all sound different to steel.
    6. Use a tensegrity structure. http://en.wikipedia.org/wiki/Tensegrity
  5. Mar 1, 2014 #4
    Thanks guys for that..I am now looking for any online app for testing/simulating my truss-bridge. Is there any free app with decent features?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook