What is the shear force diagram actually used for?

[Marts12]

Hi there,

I have created lots of shear force and bending moment diagrams for simply supported beams. I have used the maximum value on the bending mement diagram for bending and stress equations, but I have never found any real use for the shear force diagram. Yes they tell you the distribution of shear force along a beam but what can that be used for?

 

[SteamKing]

They are used in case you need to calculate the shear stress in a beam, or perhaps a combined bending and shear stress at a certain location.
Also, the area under the shear force curve gives you the bending moment acting on the beam.

 

[Marts12]

Thank you very much for your response SteamKing, it was very usefull.

Just one other thing in relation to this topic, I have attached a basic representation of a shear force diagram. You will see that the shear force line passes vertically through the zero line, how would the shear force acting on the beam be described at this point?

 

[SteamKing]

Thank you very much for your response SteamKing, it was very usefull.

Just one other thing in relation to this topic, I have attached a basic representation of a shear force diagram. You will see that the shear force line passes vertically through the zero line, how would the shear force acting on the beam be described at this point?

There is a discontinuity in the shear force values due either to a concentrated load or to a reaction applied at that point. To the left of the discontinuity, the shear force values are some constant positive value; to the right, the shear force values are some constant negative value. The difference in the magnitudes of the shear force on either side of the discontinuity will equal the magnitude of the applied load or of the reaction.