Double Overhanging Beam 1

[bidga1]

Hi

I am an apprentice engineer trying to learn about beam, and beam bending.

I have done a little presentation analysing a double overhanging beam. Please could one of you wonderful seasoned Engineers let me know if I have got it correct?

The first image is of the beam with 2 point loads of 20Kn and a UDL of 50KNm

The second image shows the moments and reactions

The 3rd image shows the shear force diagram

Finally the 4th image shows the bending moment diagram - using the areas under the various stages of the Shear force diagram

I've tried to make it as clear as possible but hope that you will be critical with your comments.

Many thanks

 

[rb1957]

one obvious (and trivial) observation is the spans are not to scale.

one obvious problem is your reactions don't balance the applied loads ...
140kn applied, 90kN reacted.
this is something you should've done yourself.

it looks as though you've applied the 50kN/m over only 1m (not 2m as shown).

sumMa ... 4B = -80+40+100*5, B = 115kN
sumMb ... 4A = -100+40+160, A = 25kN

the rest is "trivial".

another day in paradise, or is paradise one day closer ?

 

[bidga1]

I thought you applied the UDL as a point load at the midpoint of the span? i.e. 50Kn x 1. Therefore there is is 90 kN applied?

Thank you for the feedback

 

[rb1957]

you can (for the purposes of getting external reactions) replace a UDL with a point load at the centroid but the load is 50kN/m*2m.

For internal shears and moments you should carefully apply the method of cuts to the loading (as you have done).

I think you can fudge the problem to get your reactions ...
if 25kN/m applied to the RH overhang, then ...
sumMa ... 4B = -80+40+50*5 ... B = 57.5 kN
sumMb ... 4A = -50+40+160 ... A = 37.5 kN
applied load = 90 kN = sum reactions.

another day in paradise, or is paradise one day closer ?

 

[bidga1]

Thanks ever so much for your help