Master Shear Force Diagrams with this Helpful Homework Example

In summary, the conversation is about drawing a Shear Force Diagram for a beam with a UDL. The person is struggling with where to start the diagram and is unsure if their attempt is correct. They are advised to draw it on squared paper to better understand the gradient of the graph and are given a link to check their answer. It is also mentioned that the SFD must go back down to 0 at the free end of the beam.
  • #1
ryanmcarthy
20
0

Homework Statement


Hi,
I know how to draw simple Shear Force Diagrams, but I am struggling with the example in the below picture, as it has a UDL.


Homework Equations



ShearForce2.jpg



The Attempt at a Solution



Normally for the solution, I should start the diagram at 26.7, then across and down to 16.7, then across and up to 70, then across and down to 50.

But as it has a UDL I know this changes things! How do I start the diagram, and I will have a go at doing it. Do I start at 26.7, or do I need to do something before this?


Thanks a lot
 
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  • #2
I've come up with this, but don't know if I started correctly?

Diagram1.jpg
 
  • #3
The left half is correct. In the 5m stretch between the 10 kN load and the Reaction R2, what would you expect the change of shear force to be? The figure of -28.7 seems wrong to me. As the final result on the right is not 20 kN, you know you have gone wrong. I recommend you draw this to scale on squared paper. In that case, you should see the gradient of the graph is the same throughout.
 
  • #4
Thanks a lot for the relpy! I can't draw it on square paper, as I am at home and don't have a scanner (only at work).

Is this attempt better? I'm not sure if I need to go down to zero at the end though?

ShearForce3.jpg


Thanks
 
  • #5
That is now correct, you can check your answer here,

http://learntoengineer.com/beam?f=2,u1|8,u2|3,-10|10,-20&d=0,10!-5&m=

The SFD does have to go back down to 0 at the end. The shear force and bending moment of any beam is 0 at a free end.
 
Last edited by a moderator:
  • #6
Hi,

Thanks a lot for the help!
 

FAQ: Master Shear Force Diagrams with this Helpful Homework Example

What is a shear force diagram?

A shear force diagram is a graphical representation of the shear forces acting on a beam or structural element. It shows the magnitude and direction of the shear forces at different points along the length of the beam.

Why is a shear force diagram important?

A shear force diagram is important because it helps engineers and designers understand how external loads and internal forces are distributed within a structure. This information is crucial for ensuring the safety and stability of the structure.

How do you draw a shear force diagram?

To draw a shear force diagram, you first need to calculate the shear force at different points along the beam using equations or mathematical software. Then, plot these values on a graph with the distance along the beam on the x-axis and the shear force on the y-axis.

What are the key features of a shear force diagram?

The key features of a shear force diagram include the shear force at different points along the beam, the location of the maximum shear force, and the points where the shear force changes direction (i.e. where the shear force is zero).

What is the relationship between a shear force diagram and a bending moment diagram?

A shear force diagram and a bending moment diagram are closely related and are often drawn together. The shear force diagram shows the changes in shear force along the beam, while the bending moment diagram shows the changes in bending moment. These diagrams can provide valuable information about the internal forces and stresses within a structure.

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