Internal Forces on a Truss (Again)

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SUMMARY

The discussion focuses on calculating the internal force in member BC of a truss structure with pin supports at joints A and D. The user successfully applied equilibrium equations to determine forces in the y-direction and calculated the angle between members AE and AB as 26.57 degrees. However, they encountered difficulties in resolving further internal forces due to multiple unknowns at other joints. The forum participants provided feedback on potential errors in calculations and sought clarification on the geometry of the truss members.

PREREQUISITES
  • Understanding of static equilibrium equations in truss analysis
  • Basic trigonometry for angle calculations
  • Knowledge of internal force resolution in structural members
  • Familiarity with pin support mechanics in truss systems
NEXT STEPS
  • Review the method of joints for truss analysis
  • Learn about the method of sections for calculating internal forces
  • Study the effects of symmetry in truss structures
  • Explore common mistakes in resolving forces in trusses
USEFUL FOR

Engineering students, structural analysts, and anyone involved in truss design and analysis will benefit from this discussion, particularly those seeking to improve their understanding of internal force calculations in truss systems.

smrgn92
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Homework Statement



Hello, in the attached file shows a picture of the problem I need to resolve. The question asks to calculate the internal force in the member BC. There is a pin support located at joint A and D, which is not shown in my diagram, and it is also symmetrical, which makes things slightly easier.

Homework Equations



See attached file.

The Attempt at a Solution



I calculated the forces in the y direction using the equilibrium equation, and then calculated the angle between member AE and AB using basic trigonometry to be 26.57 degrees. I then resolved the internal forces in members AE and AB. However, I am unable to determine what else I can do with resolving further internal forces in this structure. For all other joints, there are at least 2 unknown forces, for which I am unable to determine any other internal forces. What should be my next approach? Thanks, forum.
 

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smrgn92 said:

Homework Statement



Hello, in the attached file shows a picture of the problem I need to resolve. The question asks to calculate the internal force in the member BC. There is a pin support located at joint A and D, which is not shown in my diagram, and it is also symmetrical, which makes things slightly easier.

Homework Equations



See attached file.

The Attempt at a Solution



I calculated the forces in the y direction using the equilibrium equation, and then calculated the angle between member AE and AB using basic trigonometry to be 26.57 degrees. I then resolved the internal forces in members AE and AB. However, I am unable to determine what else I can do with resolving further internal forces in this structure. For all other joints, there are at least 2 unknown forces, for which I am unable to determine any other internal forces. What should be my next approach? Thanks, forum.
You have an error in getting FAB.
upload_2015-7-12_20-53-57.png

You changed the cosine back into the sine .Also, can you clarify?
Is member EB perpendicular to member AG ?
 
Thank you, silly mistake there. And I'm not entirely sure, the question doesn't specify, but I'm assuming it is.
 

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