What is the formula for calculating frame deflection in a beam problem?

AI Thread Summary
The formula for calculating frame deflection in a beam problem is confirmed to be (4F(L^3))/3EI, as stated in the textbook. The initial attempt at a solution yielded (2FL^3)/3EI, which did not account for the deflection at point E in the y direction. After considering the deflection contributions from both forces at E and F, the correct total deflection was derived. This discussion highlights the importance of considering all points of deflection in beam problems. The final consensus is that the total deflection formula is indeed (4F(L^3))/3EI.
hatchelhoff
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Homework Statement


X_FRAME.PNG


Homework Equations


The answer in the book is (4F(L^3))/3EI

The Attempt at a Solution


I felt the above question could be simplified into a standard beam problem. I choose the following beam.
Simple Support.PNG


I used the Yc equation, but when I replace a with L I get an answer of (2FL(^3))/3EI
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You seem to be ignoring the deflection of E in the y direction. That will increase the deflection at C.
hatchelhoff said:

Homework Statement


View attachment 215748

Homework Equations


The answer in the book is (4F(L^3))/3EI

The Attempt at a Solution


I felt the above question could be simplified into a standard beam problem. I choose the following beam.
View attachment 215749

I used the Yc equation, but when I replace a with L I get an answer of (2FL(^3))/3EI[/B]
 
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pongo38 said:
You seem to be ignoring the deflection of E in the y direction. That will increase the deflection at C.
Thanks pongo38. I have taken into account the deflection at E due to F and due to Ra. this gives me 2FL(^3))/3EI.
I then add this to the deflection at F. This gives me a total of 4FL(^3))/3EI.
 
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