How to Determine Forces in a 2D Truss Using the Joint Method?

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Discussion Overview

The discussion revolves around determining the forces in a 2D truss using the joint method, focusing on a specific homework problem related to engineering mechanics. Participants share their attempts at solutions and seek clarification on the methodology and calculations involved.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant presents their calculated forces for each member of the truss, indicating whether the forces are tensile (T) or compressive (C).
  • Another participant suggests that the geometry used for member DE is incorrect, specifically noting the rise and run measurements.
  • There is an emphasis on the importance of determining joint support reactions first using equilibrium equations before applying the joint method.
  • A later reply expresses appreciation for the feedback and acknowledges confusion regarding the trigonometric calculations involved.

Areas of Agreement / Disagreement

Participants express differing views on the correctness of the geometry used in the calculations, and there is no consensus on the accuracy of the initial answers provided. The discussion remains unresolved regarding the specific values and methods used.

Contextual Notes

Some limitations include potential errors in geometry assumptions and the need for clarity on the equilibrium equations before applying the joint method. The discussion does not resolve these issues.

togo
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Homework Statement


2lw4x1g.jpg


Determine force of each member using joint method

Homework Equations


T = F x D


The Attempt at a Solution


2ytuvme.jpg


Answers are:

Fab 2465 T
Fbd 1200 T
Fbc 1375 C
Fdc 750 C
Fde 860 T (This one is what I tried)
Fce 649 C
Fac 1922 C

Thanks.
 
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I moved this thread to the engineering homework forum as you're more likely to get responses on this type of problem there.

You might want to forgo using a scanned image of your work, especially one so large, since it makes your post inconvenient to read.
 
togo said:
Determine force of each member using joint method

Homework Equations


T = F x D


The Attempt at a Solution


Answers are:

Fab 2465 T
Fbd 1200 T
Fbc 1375 C
Fdc 750 C
Fde 860 T (This one is what I tried)
Fce 649 C
Fac 1922 C

Thanks.
You have the wrong geometry for the slope of member DE...the rise is 20 but the run is 25, not 55...

Always determine joint support reactions first using the equilibrium equations; then start at the easiest joints next when determining forces using the method of joints. Also be sure to indicate T (force of member on joint pulls away from joint) or C (force of member on joint pushes toward joint).
 
thanks for that, encouraging to know I'm on the right track. Something did seem wrong with the trig
 

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