Will truss linkages diminish vibrations?

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    Truss Vibrations
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Discussion Overview

The discussion revolves around the potential of truss linkages to diminish vibrations and isolate a platform from stresses and impulses. Participants explore theoretical and practical aspects of how such structures might attenuate or transmit impulses, considering various design elements and materials.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether a platform supported by truss linkages can be isolated from impulses acting on the linkages, suggesting the possibility of significant reduction in impulse magnitude.
  • Another participant argues that unless real-world effects like slippage and flex are considered, impulses will be transmitted faithfully through a rigid assembly, indicating the need for loss elements to attenuate impulses.
  • A different perspective suggests analyzing the structure as a transmission line network and proposes several methods to reduce impulse amplitude, including varying path lengths, using knee joints to prevent axial wave propagation, and incorporating materials with different acoustic properties.
  • One participant expresses a need for online applications to test or simulate truss-bridge designs, seeking recommendations for free tools with decent features.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the effectiveness of truss linkages in isolating vibrations, with multiple competing views on the mechanisms involved and the necessity of additional design elements for impulse attenuation.

Contextual Notes

Limitations include the dependence on real-world factors such as material properties and structural design, as well as unresolved questions about the specific configurations that might effectively reduce vibrations.

Who May Find This Useful

Individuals interested in structural engineering, vibration analysis, and design of truss systems may find this discussion relevant.

Varadha
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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?
 
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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.
 
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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
 
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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?
 

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