Confused on Calculating Deflection and Rotation for Non-Prismatic Beam?

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In summary, the student is struggling with finding the value of delta in a 2X1 array of -d and -theta. They initially tried integrating equations for deflection and rotation, but got large answers. They then used the equations with the integral of I(x)dx, which gave reasonable deflections but a resulting shear force of only 0.2kip on the right. The student is asking for assistance in finding where they went wrong and mentions using a different method to solve the problem.
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Homework Statement


COMP1beam.jpg



Homework Equations


[k]{delta}=F


The Attempt at a Solution


I found I(x) and confirmed it manually. Basically, I think my confusion comes when finding delta. Delta is a 2X1 array of -d and -theta, respectively. I used equations for deflection and rotation for a prismatic beam that's uniformly loaded...

dmax=-wL^4/(8EI)
thetamax=-wL^3/(6EI)

initially, i integrated the above equations WRT x, along the length 0-->L (with I=I(x) of course), but that gave me absurdly large answers. So then I used the above equations with I=integral(I(x)dx). This gave me reasonable deflections, but it left me with a resulting shear force of only 0.2kip on the right. equating vertical forces to 0 leaves me with a shear of 59.8kip on the left. This cannot be correct.

I can't seem to figure out what I am doing wrong, but once i get it, i shouldn't have a problem calculating the FEFs for w2. can someone please take a look, and let me know where I am going wrong? Thanks!
 
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  • #2
Ha, I meant E=5000ksi in the problem statement; my apologies.
 
  • #3
Tried doing it a different way and got it to work
 

FAQ: Confused on Calculating Deflection and Rotation for Non-Prismatic Beam?

What is the FEF of a non-prismatic beam?

The FEF (flexural rigidity enhancement factor) of a non-prismatic beam is a dimensionless quantity that represents the ratio of the beam's actual flexural rigidity to its ideal flexural rigidity.

How is the FEF of a non-prismatic beam calculated?

The FEF of a non-prismatic beam is calculated by dividing the beam's actual flexural rigidity by its ideal flexural rigidity. The ideal flexural rigidity is calculated by assuming that the beam is prismatic (uniform cross-section) along its entire length.

What factors affect the FEF of a non-prismatic beam?

The FEF of a non-prismatic beam is affected by several factors, including the stiffness and geometry of the beam's cross-section, the material properties of the beam, and the distribution of bending moment along the beam's length.

Why is the FEF of a non-prismatic beam important?

The FEF of a non-prismatic beam is important because it allows for a more accurate calculation of the beam's deflection and stress under load. It also helps in designing more efficient and cost-effective structures by optimizing the beam's shape and dimensions.

How can the FEF of a non-prismatic beam be improved?

The FEF of a non-prismatic beam can be improved by selecting a more appropriate cross-section and material for the beam, as well as by varying the beam's geometry along its length to better distribute the bending moment and reduce stress concentrations.

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