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1-Visitor
Sep 2, 2014 1:11 PM UTC
Question

RE Bending moment and shear force diagram

Almost there guys.

I've manage to draw the shear force diagram from some given numbers, I'm now trying to plot the bending moment diagram but for some reason I'm getting an error on the moment axis.

any suggestions or assistance would be greatly appreciated.

15 replies

19-Tanzanite
Sep 2, 2014 1:38 PM UTC

M is a function of x, so you should have x.m on one axis and M(x.m) on the other.

However, you have an error in the definition of M. W is a two element vector, but i ranges from 1 to 4, so the index is out of range.

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gbradley1-VisitorAuthor
1-Visitor
Sep 2, 2014 1:51 PM UTC

Thanks Richard, I'll have a look and get back to you

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23-Emerald I
Sep 2, 2014 2:06 PM UTC

There's an easier, more general way to do this type of problem; vectors for plotting are poor for this.

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gbradley1-VisitorAuthor
1-Visitor
Sep 2, 2014 2:21 PM UTC

Thanks Fred, although the way you've shown is the generally way to do this. with the vectors, the mathcad sheet can be given to someone with hardly any knowledge of mathcad. so the only thing they need to do is add as many point loads and UDL's to the span of the beam and the sheet will work it out.

They don't need to go into the formula's to re write the equation.

See new attachment with the original problem

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23-Emerald I
Sep 2, 2014 3:15 PM UTC

So your challenge is to write the functions from the vectors . . .

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gbradley1-VisitorAuthor
1-Visitor
Sep 2, 2014 3:47 PM UTC

Thanks Guys, shear force and bending moment diagram drawn, two more questions, how can a invert the graph so the bending moment and shear are the other way?

and how do I change the units to kN.m and m to the graph.. you can see the numbers at present are not correct

model attached

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19-Tanzanite
Sep 2, 2014 3:56 PM UTC

Divide the variables on the axes by the appropriate unit. Then type limits into the top and bottom placeholders on the y-axis.

invert graph.png

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gbradley1-VisitorAuthor
1-Visitor
Sep 2, 2014 4:03 PM UTC

Thanks Rich, is that the only way to invert the graph by typing the upper and lower limits in the place holders

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