What is the Correct Value of Dx in Frame Analysis?

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Homework Help Overview

The discussion revolves around a frame analysis problem, focusing on determining the correct value of Dx. Participants are examining the equilibrium equations and the forces acting on various members of the frame.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the equilibrium equations for the frame, noting attempts to solve for unknown forces. There is questioning of the assumptions regarding the direction of forces acting along members, particularly at point B. Some participants express difficulty in isolating members due to multiple unknowns.

Discussion Status

The discussion is active, with participants exploring different interpretations of the problem. One participant indicates a breakthrough in understanding by summing moments about point C to isolate unknowns, while others continue to question the assumptions made in their approaches.

Contextual Notes

There are indications of missing information regarding the forces acting on members and the constraints of the problem, as well as the complexity introduced by multiple unknowns in the analysis.

yaro99
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Homework Statement


pErlIgy.png



Homework Equations


ƩFx=0
ƩFy=0
ƩM=0


The Attempt at a Solution



For the entire frame:
ƩMA = 0: -360*15 -240*33 + E*12 = 0
E = 1110 lb →
ƩFx = 0: 1110 - Ax = 0
Ax = 1110 lb ←
These are the correct values so far.

Member BC:
W0a04tA.png


By = (4/3)*Bx

ƩMC=0: -240*9 + 360*9 + Bx*12 - (4/3)*Bx*18 = 0
Bx = 90 lb
By = (4/3)*90 = 120 lb

These values are incorrect.
 
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Does the force at B necessarily act along the member as you have assumed?
 
TSny said:
Does the force at B necessarily act along the member as you have assumed?

Hmm I guess it doesn't.
But I can't find another way of doing the problem. Every member seems to have 4 unknowns when isolated.
 
What can you learn from CDE?
 
TSny said:
What can you learn from CDE?

Ah, I figured it out now, thanks!

I only need the value of Dx so I summed the moments about C.
Then I solved for the three unknowns left on ABD.
 

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