Need help clarifying statics problem.

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SUMMARY

The discussion centers on solving for the internal force in member BC of a truss structure. The user successfully calculated the reaction forces at points A and D but struggles with the methodology for analyzing member BC. It is established that taking moments is essential due to the presence of bending in the horizontal and vertical members, which complicates the analysis. The user is advised to include the horizontal force component at D when creating free body diagrams (FBD) for accurate calculations.

PREREQUISITES
  • Understanding of static equilibrium principles
  • Familiarity with free body diagrams (FBD)
  • Knowledge of truss analysis methods
  • Basic concepts of bending in structural members
NEXT STEPS
  • Study the method of joints in truss analysis
  • Learn about calculating moments in static systems
  • Explore the effects of bending on structural members
  • Review examples of free body diagrams for complex truss structures
USEFUL FOR

Students in civil or mechanical engineering, structural analysts, and anyone involved in truss design and analysis will benefit from this discussion.

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Homework Statement


What is the magnitude of the internal force in member BC?

Homework Equations


So I figured out the reaction force at A and D by taking the moments about point A to find the vertical force at D and then summing the x and y components to find the forces at A.

The Attempt at a Solution



So I solved for the reaction forces for A, and D already. Why can't I split the truss into three members? Why can't I take member AD and have a free body diagram for that member and solve for the Fx and Fy for Bx and By by summing the forces? Do I absolutely have to take the moment? Can I not do

Ax-Bx=0
Ay-By+Dy=0

To find the components of B? This method doesn't seem to work.
Why do I have to take the moment?
 
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This is not a pure truss since the horizontal and vertical members are subject to bending. When taking a FBD of AD, you must include the horizontal component of force at D, found by first taking a FBD of the vertical member.
 

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