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

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SUMMARY

The discussion focuses on determining the force components in specific members of a loaded truss, specifically members AD, CD, AB, BC, and BD. The user has successfully calculated the upward components at joints A and C, identifying a force of 900 lb upward and a resultant force of 1540 lb using cotan(30.3). The user seeks clarification on identifying the nature of forces (compression or tension) in the remaining members and emphasizes the importance of free body diagrams and equilibrium equations in analyzing truss forces.

PREREQUISITES
  • Understanding of truss structures and their components
  • Familiarity with equilibrium equations in static analysis
  • Knowledge of free body diagrams for force analysis
  • Basic trigonometry, specifically cotangent functions
NEXT STEPS
  • Study the method of joints for analyzing truss forces
  • Learn about the method of sections for determining internal forces in trusses
  • Explore the use of free body diagrams in static equilibrium problems
  • Review concepts of tension and compression in structural analysis
USEFUL FOR

Engineering students, structural analysts, and anyone involved in the design or analysis of truss structures will benefit from this discussion.

SteelDirigibl
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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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