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HOMEWORK 27.B - SUM 24
14 thoughts on “HOMEWORK 27.B - SUM 24”
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I split the beam into two sections at point B. I know I would ignore the force at point B itself, but what about the moment? Would I ignore it too, and if not, would it be factored into my calculation on the left segment of the beam or the right segment?
Update: I think I figured it out (or at the very least, my answer got me a bending moment diagram that made sense):
All forces AND moments are ignored IF you don't include them in your x. So when I made my cut at 2L/3, my x was 0 <= x < 2L/3, so I would have included the M moment but NOT the 2M moment as the 2M moment is at 2L/3 and therefore is not included in the equation.
Putting this here because this took me an embarassingly long time to figure out. :/
Ignore the force and moment at the most right point since the segment is 0<x<most right point. Another way to think is we will cut infinite times in the segment, whenever we cut at x, where 0<x<most right point, the left part where we are doing calculations won't include the forces and moments at the most right point.
A good way to think about it is that you are calculating the distance up to but not at that point. Then you just add the positive moment, shear force and normal force, and then solve the equilibrium equations accordingly.
When solving for the Bending Moment about segment 3 (6ft to 9ft), do we also include the moment about point B (2M) in our calculations?
Yes, I believe so, what I would do is solve for x=0, then x = any number between 0 and 6, then x =6 for the first section. When solving at x=6 for section AB you don't have to include the moment about point B. Then for section BD you should solve for two more points this time using the moment about point B. I also think you could do this the opposite way and do the cuts from 0 to 2L/3 and include the point 2L/3. Then do the second cut from 2L/3 to L but not including the point 2L/3.
That's what I did as well.
Are we just supposed to draw the diagrams or do we need to show the calculations for the final answer?
I think having calculations for work would probably be best
I believe that you would have still needed to have diagrams of each section you did your calculations for to get full credit.
For clarification, is A is pin joint and B a roller joint or are they both pin joints?
I put A as a pin joint and B as a roller joint for my calculations.
I am assuming that in order to get full credit for this problem you need to show all work. I showed the work to solve for the reactions at the supports and then the work for each segment to calculate the shear force and bending moment. Also, A is a pin joint and B is a roller joint. You can tell that B is a roller joint since there are wheels visible at the bottom of it while A does not have those included.
Here is my solution process for problem 27A (not 27B), to those of you who might want.
https://p.sda1.dev/18/94d3a042d12a926dc99c507965c0ec06/1721729386925.jpg