Find Reactions to Overhanging Beam

[Ozkan Suna]

The question is:

How do I find all the reactions? I haven't worked with a similar problem before, so I'm kinda confused. Hope someone will help!

Thanks from now.

 

[mfb]

Finding all forces should be easy from the sketch. To calculate their values: Both net force overall and torque around a point of your choice have to be zero in equilibrium.

 

[Ozkan Suna]

'' Point of my choice has to be zero '' Does it mean I have to add a charnier? Sorry for the confusion

 

[mfb]

You don't have to add anything. Pick a random point. Calculate all torques around that point from all the forces. The sum has to be zero.

 

[Ozkan Suna]

So if I want the moment ΣMz = 0; Dy * 6a - P*10a - p*5a*2,5a = 0
and then isolate Dy and substitute it in ΣFy = 0; By + Dy = 5ap + P??

 

[mfb]

If you introduce new variables, you should define them somewhere. An explanation what is what would be useful as well.

P*10a

Why 10a?

- p*5a*2,5a

","? And assuming you mean 2.5, why 2.5?

and then isolate Dy and substitute it in ΣFy = 0; By + Dy = 5ap + P??

Sure.

 

[Ozkan Suna]

1) We have a single force at the end of the beam. So I say the force multiplied with the total lenght.

2) From the left side of the beam to the half we have distributed load. So I want to find where the single force attacks, and that is on the half on the beam, right?

Sorry for my bad English!

 

[mfb]

2) From the left side of the beam to the half we have distributed load. So I want to find where the single force attacks, and that is on the half on the beam, right?

What is the middle between "2a to the left" and "3a to the right"?

 

[Ozkan Suna]

Oh, so we have to split it up to 2a/2 = a and 3a/2 = 1.5a?

 

[mfb]

You can split it in two pieces, but simply finding the middle works as well. The middle is not 2.5 a to the right of the support.

 

[Ozkan Suna]

1.5 a right?

 

[mfb]

No.

Draw it on a piece of paper if that helps. Or use signs: Where is the middle between -2 and +3?

 

[Ozkan Suna]

a?

 

[mfb]

Stop guessing please. How do you calculate the average between two values?

 

[Ozkan Suna]

Not guessing, it's confusion.
The average of -2 and 3 is: -2 + 3 / 2 = 1/2

 

[mfb]

Right.