Deflection of L Shaped Cantilever Beam

Click For Summary

Discussion Overview

The discussion revolves around determining the horizontal and vertical deflection of point C on an L-shaped cantilever beam, including the angle of deflection. Participants explore various methods and equations related to beam deflection, addressing both theoretical and practical aspects of the problem.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant proposes using the equation δv = ML^2/2EI to find vertical deflection and suggests replacing the moment with an equivalent point load at C to simplify calculations.
  • Another participant challenges the validity of replacing a torque with a force, arguing that it may not accurately represent the system's equilibrium and that a torque applied to one segment affects the others differently.
  • A different participant notes that the applied torque is transferred unchanged to the anchoring point A, where a reactive moment appears, indicating that the deflection depends on the lengths of the L-shaped parts.
  • There is a clarification about the relationship between the moments and displacements, with one participant emphasizing the distinction between horizontal and vertical displacements of points B and C.

Areas of Agreement / Disagreement

Participants express differing views on the method of analyzing the deflections and the appropriateness of replacing moments with equivalent loads. The discussion remains unresolved, with multiple competing perspectives on the correct approach to the problem.

Contextual Notes

Participants have not reached consensus on the assumptions regarding the application of torques and forces, and there are unresolved questions about the dependency of deflections on the lengths of the beam segments.

Wil_K
Messages
1
Reaction score
0

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.
 

Attachments

  • L_beam.jpg
    L_beam.jpg
    6.6 KB · Views: 3,447
Physics news on Phys.org
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.
 
  • Like
Likes   Reactions: Chestermiller
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.
 

Similar threads

Replies
3
Views
2K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 11 ·
Replies
11
Views
3K
  • · Replies 5 ·
Replies
5
Views
4K
  • · Replies 3 ·
Replies
3
Views
8K
  • · Replies 17 ·
Replies
17
Views
3K
Replies
3
Views
13K
  • · Replies 1 ·
Replies
1
Views
2K
Replies
3
Views
3K
  • · Replies 3 ·
Replies
3
Views
3K