Internal Forces on a Truss (Again)

AI Thread 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 has successfully calculated forces in the y direction and determined the angle between members AE and AB but is struggling to resolve further internal forces due to multiple unknowns at other joints. Forum participants point out an error in the user's calculations, specifically regarding the use of sine and cosine, and seek clarification on the perpendicularity of member EB to member AG. The user is looking for guidance on the next steps to take in solving the problem. The conversation highlights common challenges in analyzing truss structures and the importance of accurate calculations.
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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