Learning Forum

[Rameez_ul_Haq]

So I used line bodies to simplify my model (to be used in place of a bolt) and I selected a direction for that line body using a path. I retrieved a graph for shear forces and moments after conducting a static structural analysis. However, if I reverse the direction for the path on that line body, the maximum shear force remains the same but the I am seeing a change in the maximum moments encountered. Can anyone tell me why is this happening?

I was hoping the graph to be simply reversed by reversing the path since the line body needs to be in equilibrium. But this was not what I saw and I am mystified.

[Rameez_ul_Haq]

Can someone help me on this one?

[Rameez_ul_Haq]

,would like to provide some help on this one please?

[1shan]

I tried a simple analysis with line bodies but could not replicate your issue. I get the same values for both directions. Could you share some images of the result, model and the shear moment diagram, for both directions. Maybe the issue is model specific.
Regards Ishan.

[Rameez_ul_Haq]

,I thought you might have already experienced this kind of issue before and you already have an idea about this like why is this happening.
I unfrotunately cannot post the whole model pictures, but I can post the ones shown below.
DESIGN MODULER Line body Direction:

PATH:

Shear Force and Moment graph:
PATH Flipped:

Shear force and Moment graph for flipped path:
The maximum shear force and displacement is same for both cases, but the maximum moment is changing. This confuses me.

[1shan]

Looks like only one direction gives you the correct result. If you animate the above result you will find something like the image below -
Use the default direction, this gives you the correct result.

Regards Ishan.

[Rameez_ul_Haq]

thankyou for clearing this issue out.
I am also gonnna ask you one more thing. Assume I create a line body between two holes of different solid bodies, and I load one of the solid bodies. What I have learned in my university life is that in static analysis, all the bodies must be in equilibrium. So it it natural to assume that the shear force and moment at that point of the line body which is joined to one solid body's hole, must be equal to the shear force and moment at the other point of the line body which is joined to other solid body's hole. (Ofcourse, assuming that no extra forces and moments are acting on that line body itself). However, sometimes when I see observe the shear force and moment diagram of this kind of line body, I see a difference in these two values as shown in the picture below.
Like I was expecting the S1 and S2 values to be equal, and also M1 and M2 values to be the same. However, there exists a difference which is very evident. The analysis from where this graph is retrieved is not complex at all. Can you tell me why does this happen? Is it supposed to be like this, or this is some kind of numerical error?

[1shan]

Good question !! Lets take a simple example of a cantilever beam (length L) with a point load (F)at the end. What is the bending moment at the loaded end? Zero right? While the bending moment at the fixed end is F*L. But the beam is still in equilibrium. Why does that happen :) ?
Regards Ishan.

[Rameez_ul_Haq]

,yeah the beam is in equilibirum because the internal moments at the right end and left end of a cross-section of that beam should always be equal but opposite.

[1shan]

Yes, the total moment should be zero while bending moments can be unequal at both ends.
Regards.

[Rameez_ul_Haq]

,yeah got it :) But why are the shear forces different then at both the ends?

[Rameez_ul_Haq]

,can you please comment on this?

[1shan]

Don't you think the same reason should hold? Lets say you have a simply supported beam on both ends. You add a force (anywhere other than the center). You will find the shear force one one end is more than the other. The best way would be to use reaction probes and see if the net force sums to zero.
Ishan.

[Rameez_ul_Haq]

,yes exactly. I completely comprehend what you are saying. But the case that I showed here, the force is applied (or in other words, taken from the hole of a solid body) on one end of the line body, so shouldn't the other end of the same line body have the same value of shear force? Thats not what I see in the shear force graph that I shared. Btw, no other connection was present or external force was applied on that line body other than the mentioned.

[Rameez_ul_Haq]

,could you please tell your views on this?

[Rameez_ul_Haq]

,would you like to add something here?

[1shan]

"But the case that I showed here, the force is applied (or in other words, taken from the hole of a solid body) on one end of the line body, so shouldn't the other end of the same line body have the same value of shear force?" - Looks like your shear force is changing significantly from the left to the center. This cant be a cantilever case with point load at the end. Please check
Regards
Ishan.

[Rameez_ul_Haq]

,I re-checked but it is. Just a line body, with end points connected to each hole of a separate solid body. Nothing else. Should I regard this difference in the force between the two as a numerical error?