Deflection by integration of load equation

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Discussion Overview

The discussion focuses on determining the deflection curve equation for a cantilever beam subjected to a sinusoidal load. Participants explore the boundary conditions relevant to the cantilever setup compared to a simply supported beam, examining how these conditions affect the solution process.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant proposes that the primary difference between the cantilever and simply supported beam problems lies in the boundary conditions used to solve for constants in the deflection equation.
  • Another participant clarifies the boundary conditions for a cantilever beam, noting that at the fixed end (x=0), both the deflection and the angle of deflection are zero, while questioning what conditions apply at the free end.
  • A later reply corrects an earlier claim about the moment at the fixed end, stating that it is not zero, and emphasizes the need to consider the shear force and moment conditions at the free end (x=L).

Areas of Agreement / Disagreement

Participants generally agree on the importance of boundary conditions in determining the deflection curve, but there is some uncertainty regarding the specific conditions at the free end of the cantilever beam.

Contextual Notes

Participants have not fully resolved the implications of the boundary conditions at the free end, and there may be additional assumptions or definitions that are not explicitly stated.

Freyster98
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Homework Statement



Determine the equation for the deflection curve for the cantilever supported at A with a load given by: q=q0*sin(\pix/L).

Homework Equations





The Attempt at a Solution



I think this is pretty straightforward, but want to be sure. I did a similar problem with a simply supported beam with the same load equation, shown in the attached diagram. Am I safe to assume that the ONLY difference in this problem with a cantilever is the boundary conditions used to solve for C1, C2, etc?

The boundary conditions would be:
at x=0,y=0...and at x=0,moment=0.
right?
 

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Right, typically you say to yourself what is zero at the boundaries. For a simply supported beam, the deflections are zero; for a fixed-fixed beam, both deflections and angles are zero. In the case of a cantilevered beam, on the fixed end you have zero angle and zero deflection, but the million dollar question is what is zero at the free end?
 
minger said:
Right, typically you say to yourself what is zero at the boundaries. For a simply supported beam, the deflections are zero; for a fixed-fixed beam, both deflections and angles are zero. In the case of a cantilevered beam, on the fixed end you have zero angle and zero deflection, but the million dollar question is what is zero at the free end?

The moment, right?

Going back to my "attempt at a solution", I believe I screwed up. For the cantilever, at x=0, y=0...and at x=0, dy/dx=0. I had put that at x=0,moment=0, which is wrong. Also, I'm going to need to use: @x=L,shear force=0...and @x=L,moment=0.
 
Yup, you're right on track now. Good luck
 

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