Different diagram results

[Anonymous]

Hi!

I'm wondering about 2D Frame analysis differences. It's basically a similar problem as described here: https://forums.autodesk.com/t5/robot-structural-analysis-forum/wrong-diagram-results/td-p/5163217

When I do the frame analysis, my calculations on paper and in Robot differ a bit. I understand it is due to the differences in material stiffness. The calculations on paper indicate, that the local extremum should be 45 not 50,62. Is there any way to discard the material stiffness so I could get the same results as on paper?

[Anonymous]

Hi @Anonymous 

did you make sure to use the same young module in ROBOT and in manual calculation?

Can you attach the model?

[Anonymous]

Well while doing manual calculations I didn't choose a specific material and disregarded Young's module and I'm wondering if the same thing is possible in Robot. I'd like to see the answer in Robot not affected by Young's module (45 kNm not 50,62 kNm is the answer I'm looking for).

[Rafacascudo · Accepted solution]

It doesn´t matter  the value of E as long as it is the same for the 3 bars. Results for bar forces will be the same being it steel or concrete . Deformations will be obviously different.

You are probably seeing the result at the wrong spot. Your book is probably showing the moment(45) at midspan while Robot is showing the max moment on that span. If you create a node on midspan and ask it to show all values ,then you will get what you want. Below with concrete as material instead of steel for all 3 bars

[Anonymous]

Yeah, I just noticed that too. Thank you

[Anonymous]

I realized that you apply a release to the bar, that is why the moment is not correct, the moment diagram in the right figure is correct.