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Math Help - Bending Moments

  1. #1
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    Mar 2009
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    Newcastle upon-Tyne, England, UK
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    Exclamation Bending Moments

    Hi all
    I'm a trainee studying Civil Engineering at College.
    I am stuck on a few things and will fail my course by the end of the week if I do not get this done...

    I have a problem where I have to draw shear force diagrams and bending moment diagrams. I have done the loading diagram and the shear force diagram but am completely stuck with the bending moment diagram.

    The beam is 10m long with a 92.5kN force acting up on the left hand end, there are 2m to the 40kN/m UDL which lasts for 4m, then there is 2m to the next upward force of 77.5kN then a further 2m to the end of the beam which has a 10kN downward force on the end. I have calculated it on each metre, therefore I will end up with 10 points to plot on my bending moment diagram and each metre has been given a letter; A to K.

    I hope I have explained this well - if not I could scan a copy in but this may take me a couple of days and I don't really have a couple of days to play with.

    I have got my calculations right along the beam to the point where the 77.5kN force comes in (so I have 2 more calcs to complete then I can draw the bending moment diagram. I have no idea what to do with the 10kN force on the end. The following calculations are what I have used:

    A = 0
    B = 92.5 x 1 = 92.5
    C = 92.5 x 2 = 185
    D = (92.5 x 3) - (40 x 0.5) = 257.5
    E = (92.5 x 4) - (80 x 1) = 290
    F = (92.5 x 5) - (120 x 1.5) = 282.5
    G = (92.5 x 6) - (160 x 2) = 235
    H = (92.5 x 7) - (160 x 3) = 167.5
    I = (92.5 x 8) - (160 x 4) = 100
    J = (92.5 x 9) - ***STUCK***
    K = (92.5 x 10) - ***STUCK***

    As you can see I do not know what to do with the last 2 calcs. The last one needs to come out with 0!

    ANY help will be taken with so much thanks - as I'm a trainee, if I fail this course I will also be sacked... please help.

    Thanks for your time and in advance of any help or guidance.
    88engine
    Last edited by 88engine; March 18th 2009 at 11:38 AM. Reason: Amendment
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