Deflection of L Shaped Cantilever Beam

AI Thread Summary
To determine the deflection of point C on an L-shaped cantilever beam, the vertical deflection can be calculated using the formula δv = ML^2/2EI, with adjustments made for equivalent point loads. The moment acting about point B must be considered to find the horizontal deflection of the vertical member. It is crucial to note that replacing a torque with a force is not generally valid, as it can lead to incorrect assumptions about the system's equilibrium. Each segment of the beam contributes to the overall deflection, which depends on their respective lengths. Accurate calculations require careful consideration of the moments and displacements involved in the beam's structure.
Wil_K
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Homework Statement


I would like to know how to find the horizontal and vertical deflection of point C shown in the attached diagram. I also need to find the angle of deflection for point C.


Homework Equations





The Attempt at a Solution


I've already found a solution to this problem, but I'm not sure if it's correct. I figured that the vertical deflection can be found by analysing the horizontal member using: δv = ML^2/2EI. Then I replaced the moment with an equivalent point load acting at C, which gives the same deflection. Then I found the moment acting about point B as a result of the equivalent point load, and used the above formula to find the horizontal deflection of the vertical member.

For the total angle of deflection I just added the deflection angles for each section, which were found using: ∅= ML/EI = PL^2/2EI.

I have doubts that this is the correct solution, so it would be great if someone could steer me in the right direction.
 

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Wil_K said:
Then I replaced the moment with an equivalent point load acting at C
You cannot in general simply replace a torque with a force. It may exert the correct torque about some point, but not about all points, and it will exert a linear force which the torque did not.
A torque is applied to BC. For equilibrium of BC, AB must exert an equal and opposite torque, but no linear force, on BC. Similarly, the support at A must exert a pure torque on AB.
 
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That applied torque M is transferred unchanged all the way until reaching the anchoring point A, where a reactive equal and opposite moment appears.
The deflection of each length of the L-shaped part depends on how long each one of those is.
 
Lnewqban said:
The deflection of each length of the L-shaped part depends on how long each one of those is.
Not sure what you mean by that. The moment will bend AB, causing a displacement of B, and bend BC, causing a displacement of C relative to the displaced B.
 
haruspex said:
Not sure what you mean by that. The moment will bend AB, causing a displacement of B, and bend BC, causing a displacement of C relative to the displaced B.
Yes, I was thinking of horizontal displacement of B (and C) and vertical displacement of C.
 
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