Deflection by integration of load equation

In summary, the equation for the deflection curve for a cantilever supported at A with a load given by q=q0*sin(pi*x/L) would require the boundary conditions of y=0 and dy/dx=0 at x=0, and shear force=0 and moment=0 at x=L. These boundary conditions are different from those used for a simply supported or fixed-fixed beam, and it is important to determine the boundary conditions for each specific beam type.
  • #1
Freyster98
49
0

Homework Statement



Determine the equation for the deflection curve for the cantilever supported at A with a load given by: q=q0*sin([tex]\pi[/tex]x/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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  • #2
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?
 
  • #3
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.
 
  • #4
Yup, you're right on track now. Good luck
 

1. What is the equation for calculating deflection by integration of load?

The equation for calculating deflection by integration of load is:
δ = ∫(M(x)/EI)dx

2. What does each variable in the deflection equation represent?

The variable δ represents the deflection of the beam at a specific point. M(x) represents the bending moment at that point, which is a function of the applied load and the distance from the point. E is the modulus of elasticity of the material, and I is the moment of inertia of the cross-sectional area of the beam.

3. How is the deflection equation derived?

The deflection equation is derived from the Euler-Bernoulli beam theory, which states that the curvature of a beam is directly proportional to the bending moment at a given point. By integrating the curvature (second derivative of displacement) with respect to x, the deflection equation is obtained.

4. Can the deflection equation be used for all types of beams?

No, the deflection equation is specifically for beams that follow the assumptions of the Euler-Bernoulli beam theory, such as being made of a homogeneous material and having a constant cross-sectional shape and size along its length.

5. Are there any limitations to using the deflection equation?

Yes, there are limitations to using the deflection equation. It assumes that the beam is under linear elastic conditions and does not take into account any plastic deformation. It also does not account for shear effects or the effects of lateral loads on the beam.

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