What are the force components for each member in the loaded truss?

AI Thread Summary
The discussion focuses on determining the force components in various members of a loaded truss, specifically members AD, CD, AB, BC, and BD. The user has successfully calculated the components for AB and BC but is struggling with the others and understanding the nature of the forces as either tension or compression. Key insights include the importance of free body diagrams and equilibrium equations to ascertain force directions. It is emphasized that tension forces pull away from joints while compression forces push towards them. Overall, the conversation revolves around applying fundamental principles of static equilibrium to analyze truss forces effectively.
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Homework Statement


I need help with trusses.

Determine the force in members: (a)AD, (b)CD, (c)AB, (d)BC, (e)BD of the loaded truss. (Note: compression forces must be negative.)
Screenshot2011-03-08at110755PM.png



Homework Equations


?


The Attempt at a Solution


I found the components of AB and BC since upward components at A and C are 900 lb upward and cotan(30.3)*900 is 1540. But how do I get the components of the others? (and why/how do I know that BC is zero?
 
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well i got it figured out, but I am finding I am having trouble determining if it is compression or tension. how can I figure this out? my numbers are generally right but the opposite sign.
 


Tension forces always pull away from the joint or member on which they act, and compression forces always push toward the joint or member on which they act. Whether you use the method of joints or sections, your free body diagram will give you the direction of the force using the equilibrium equations at those joints or sections.
 

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