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## 24 thoughts on “HOMEWORK H30.A”

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Does pure bending actually occur in this diagram? From first glance, I assume halfway between A and B to B but when I do the shear and moment diagrams, I don't get a zero shear at that location, rather a constant negative shear. And to be pure bending, it's 0 shear with a moment, which no location on the beam would have. Did anyone else get something similar or am I going about this wrong?

I figured it out, nevermind.

Can pure bending just occur at a point or does it have to be occurring over some distance?

It can be at a point

Adithya is right

Does pure bending always occur at a point or sometimes occurs over a distance?

It can occur over a distance, or segment, as well.

To find I for a tubular cross section, would it just be the I of a solid circle cross section minus the I of the smaller solid circle cross section?

Yes

Do we have a reference chart anywhere of second area moments for common shapes?

believe so?

There is a reference chart of second area moments for common shapes in the textbook on page 474. Section 12.B goes into detail about the calculation of second area moments (pages 471 -475).

Thank you Jessika.

Thank you!

Professor Jones also said that you can just look them up online if you don't have the textbook.

I recommend just looking them up online.

https://en.wikipedia.org/wiki/List_of_second_moments_of_area

As far as I have understood from the lecture videos and the examples, the moment should reach 0. However, when I am trying to solve the problem, my moment was not reaching 0 on the graph. Is anyone else facing the same issue or is my understand wrong and it is not necessary for the moment to reach 0?

Moment will reach zero for this problem. So, there must be some mistake in your solution

Is it considered pure bending if the shear crosses zero due to a reaction force?

Yes it's correct. Think about in the last two HWs when you plotting the shear force diagram. You do consider the reaction force at the boundary and then create function to describe such diagram. Similarly, you need shear force diagram to help you identify the location of pure bending.

Are the pure bending moments at d and 2d from A because that's where the distributed loads stop?

No the the distributed loads stop doesn't mean the shear force stop. Try to have a look on the shear force diagram, the zero point there tells the location of the pure bending.

After finding V(x) and stating it, do I still need to write the x0 separately.

That is correct.