What is the Correct Value of Dx in Frame Analysis?

[yaro99]

Homework Statement

Homework Equations

ƩF_x=0
ƩF_y=0
ƩM=0

The Attempt at a Solution

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

Member BC:

B_y = (4/3)*B_x

ƩM_C=0: -240*9 + 360*9 + B_x*12 - (4/3)*B_x*18 = 0
B_x = 90 lb
B_y = (4/3)*90 = 120 lb

These values are incorrect.

 

[TSny]

Does the force at B necessarily act along the member as you have assumed?

 

[yaro99]

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.

 

[TSny]

What can you learn from CDE?

 

[yaro99]

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.