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I don't understand the fixed end moment AE and also fixed end moment EA ? shouldn't they be the same ?

For the fixed moment AE / fixed moment EA , shouldn't it = -10(2) +5(2) = -10 , for fixed end moment , we always assume clockwise as positive and anticlockwise as negative , right ?

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  • $\begingroup$ any sign convention can be used. however make sure u keep sign convention same for entire of project. $\endgroup$
    – Fennekin
    Commented Apr 28, 2017 at 5:12
  • $\begingroup$ given images are totally correct $\endgroup$
    – Fennekin
    Commented Apr 28, 2017 at 5:13

3 Answers 3

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What is the total distributed load applied between AE? It is $w\,\ell_{AE} = 10(2) =20$

Where is the load applied? Half way across $\frac{1}{2} \ell_{AE} = 1$

Multiply the two to get the moment of the distributed load $10(2)(1)$

The end load of $5$ is applied at a distance of $\ell_{AE} =2$

The moment of the end load is $5(2)$

The combined moment on AE is $10(2)(1)-5(2)$

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  • $\begingroup$ The moment is 10(2)(1)−5(2) = 10 anticlockwise , am i right ? In the first red circle , we can notice it's positive 10 , but in the BMD , it's negative 10 , why they have different sign ? Is anyone of them wrong ? $\endgroup$
    – utk2366
    Commented Apr 28, 2017 at 16:03
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I don't think the maximum value on span 2 is correct, it should be 8.44 and not 18.47 Check it again. Result are correct below based on 3 moments method enter image description here

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enter image description here

On the figure above and discussion below, M_xx represents the fixed end moment (FEM) when the joints are in locked/clamped/fixed condition.

Now, the structure is locked for the calculation of the fixed end moments (FEM). At the rightmost span, M_CD = M_DC = 0, since the span has no load. At the leftmost span, M_AE = 10 kNm, and M_EA = 0, why? (Pay attention to how the structure is locked and ask: Why joint E is left unlocked with load in the span? Does the load generate a moment on joint E? Why, or why not?)

Note, in structural analysis, you can use either sign convention - CW positive & CCW negative, or CW negative & CCW positive, it does not affect the results, as long as the sign convention is applied consistently to all steps of the calculation.

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