topic Re: 2D Truss analysis problem in Robot Structural Analysis Forum

2D Truss analysis problem

Anonymous — Thu, 05 Apr 2018 10:45:27 GMT

I started modeling a steel 2d truss as shown in the first picture and the results were true and actuate

but when I add columns under the truss as shown in the second picture the analysis changed

Knowing that I am using 2d truss type of structure also I tried to use 2d frame it also has the same problem

all the members are (simple bar)

I'm sure that there is a solution for this problem

Waiting for comments 😄

Re: 2D Truss analysis problem

Artur.Kosakowski — Thu, 05 Apr 2018 10:48:44 GMT

Hi @Anonymous

As far as I can see you just transferred the supports from the truss model to the bottom of the columns whereas you should keep the same boundary conditions at the columns' tops (as releases) instead.

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Re: 2D Truss analysis problem

Anonymous — Thu, 05 Apr 2018 10:56:16 GMT

You mean that I should keep the supports in the original location ???

Re: 2D Truss analysis problem

Artur.Kosakowski — Thu, 05 Apr 2018 11:00:05 GMT

Hi @Anonymous

No, what I meant was that you should define releases which correspond to the original supports at the top of the columns in your second model as by default the connections among the columns and the truss are fully fixed.

If one or more of these posts answered your question, please click Accept as Solution on the posts that helped you so others in the community can find them easily.

Re: 2D Truss analysis problem

Muhammed.OPERA — Thu, 05 Apr 2018 11:16:28 GMT

Hi @Artur.Kosakowski

I think the results will change even if you have made a releases to the top of the columns.

Re: 2D Truss analysis problem

Artur.Kosakowski — Thu, 05 Apr 2018 14:50:25 GMT

HI @Muhammed.OPERA

Why not to run a quick test?

If I managed to answer your question(s) press the Accept as Solution button please. This will help other users to find solution(s) much faster. Thank you.

Re: 2D Truss analysis problem

Anonymous — Thu, 05 Apr 2018 14:58:16 GMT

Could You show me the Fx Digram ?

Re: 2D Truss analysis problem

Artur.Kosakowski — Thu, 05 Apr 2018 15:00:37 GMT

HI @Anonymous

It is actually displayed on the picture I attached

Re: 2D Truss analysis problem

Anonymous — Thu, 05 Apr 2018 15:08:31 GMT

i see that but i want to see the values of the forces in members

i try to solve this problem by make robot understanding that the hole members of structures are tension/compression members by :

Geometry ==> Additional Attributes ==> Advanced Bar Properties

then select all the members and press ok but the values of reactions still different

Re: 2D Truss analysis problem

Artur.Kosakowski — Thu, 05 Apr 2018 15:20:18 GMT

HI @Anonymous

You can't do this for chords.

If one or more of these posts answered your question, please click Accept as Solution on the posts that helped you so others in the community can find them easily.

Re: 2D Truss analysis problem

Anonymous — Thu, 05 Apr 2018 15:24:06 GMT

you mean that the method i apply is correct but i should select specify members except the cords??

Re: 2D Truss analysis problem

Artur.Kosakowski — Thu, 05 Apr 2018 15:25:59 GMT

Hi @Anonymous

Cords and columns

If one or more of these posts answered your question, please click Accept as Solution on the posts that helped you so others in the community can find them easily.

Re: 2D Truss analysis problem

Anonymous — Thu, 05 Apr 2018 16:04:34 GMT

Thank you guys for the help

The problem solved

summary for the solution :

1-Use 2D frame type of structure

2-Use tension/compression members by :

Geometry ==> Additional Attributes ==> Advanced Bar Properties

3-Release for the column.

Finally Thanks 😄