Frame Works Trusses Homework: Determine Forces in Trusses

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SUMMARY

The discussion focuses on verifying unknown forces in a truss system, specifically analyzing a truss with individual lengths of 300mm. The user reported initial values of 100N tension and 187.5N compression, with calculated reactions of 163.5N and 130.8N. However, using the method of sections, the user obtained forces of 98.1N and 65.4N, which deviated from the expected lab value of 187N for the right box. Participants suggested considering the dead weight of the truss and using moment calculations instead of the method of sections for two pinned supports.

PREREQUISITES
  • Understanding of truss analysis principles
  • Familiarity with the method of sections in structural analysis
  • Knowledge of force equilibrium and moment calculations
  • Experience with telescopic gauges and calibration charts
NEXT STEPS
  • Study the method of joints for truss analysis
  • Learn about calculating reactions at supports in truss systems
  • Research the impact of dead weight on truss forces
  • Explore software tools for structural analysis simulations
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Engineering students, structural analysts, and professionals involved in truss design and analysis will benefit from this discussion.

Colin Luu
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Homework Statement



I need to verify a couple of unknown forces in a truss, attached image (all individual trusses are 300mm in length)

Homework Equations


Determine the forces in trusses shown.


The Attempt at a Solution


This is a lab and I've used a telescopic gauge with a calibration chart to obtain a rough value of what the forces should be, (missed too many classes on Framworks damnit!)
From Left to Right Box, Left 100N Tension, Right 187.5N Compression RL is 163.5 N Rr is 130.8N
Even is i have a parallel worked example it would be enough.
 

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okay I've done it with method of sections and resulted from left box to right 98.1N and 65.4N which is way off the lab value 187N for the right box can anyone verify these results?
 
Last edited:
We do not see the diagram yet while it is pending approval.
Could you supply your calculations how you obtained 98.1 and 65.4 N?
Have you taken into account the dead weight of the truss?
If the truss has only two pinned supports, you do not need to calculate by sections to get the reactions. Simply taking moments will do.
 
Sorry i forgot to mention this is neglecting frame weight, I'll scan the working out tonight and upload.
 

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