Axial force on beam element

[jayesh.shinde]

Hi, I am doing analysis for lattice type beam in simulation mechanical. I have imported 2D sketch for beam elements. While reviewing the results I noticed that axial force on some of the inclined beam elements are not correct. I am seeing this issue since June 2018. Before this the results were correct. Please look into this issue & guide me accordingly. Thanks, Jayesh

[John_Holtz]

Hi Jayesh,

We need some more information to understand your issue. For example,

1. Can you provide an archive of your model ("app button > Archive > Create") that demonstrates the problem along with a description of what to look at? Or some images? I suspect there is a problem in the model that is causing the problem, such as there are multiple beam elements overlapping each other.
2. When you say the problem started in June 2018, do you mean that the model that you created since June have the problem? Or do you mean that a model that you ran prior to June 2018 gave one result, and if you run the exact same model now, it gives a different result?
3. What version or versions of Sim Mech are you using?

[jayesh.shinde]

Hi John,

1. Please find attached archive of model & images. The axial force on beam element 26 should be less than axial force on beam element 10. .

2. I have worked on similar model before June 2018. Now working on new model.

3. I am using simulation mechanical 2017.

Thanks,

Jayesh

[John_Holtz]

@jayesh.shinde

Your archive is missing.

Beyond the gravity and distributed loads shown in the image, are there other loads that would change the axial force distribution?

[jayesh.shinde]

Hi John, There are no any other loads that would change the axial force distribution. Please find attached archive of model. Thanks, Jayesh

[AstroJohnPE · Accepted solution]

Hi @jayesh.shinde

I think your statement that the axial force in member 10 should be higher than in member 26 is only true for truss elements. Since you are using beam elements that transmit moments, and therefore have shear also, your statement does not need to be true.

In other words, the shear forces in all 4 beam elements at the joint also contribute to the sum of forces equal 0 at the joint, so you cannot look at the axial force by itself.

There are two other things that you should do in this type of model.

1. Your model is not statically stable -- it is free to translate in the Y direction and rotate about the Y axis. This could cause a problem in some models (even if it is not a problem in this model).
2. You should divide the members into multiple divisions since you are using beam elements.

Let us know if you have any other questions.

[jayesh.shinde · Accepted solution]

Thank you John.