topic Re: truss top member instable because of slenderness in Robot Structural Analysis Forum

truss top member instable because of slenderness

avadhprakash2023 — Wed, 24 Sep 2025 18:52:37 GMT

Hello,
I made a frame structure in which i made the top member of truss as a single member and did the analysis but all members were instable because of slenderness and then i divided it into parts with the nodes connecting web. then analysis showing it is stable. so in real world web member supporting the top member. So my question is that to divide the top member is correct way or not?

Re: truss top member instable because of slenderness

Simau — Thu, 25 Sep 2025 10:11:19 GMT

Hi @avadhprakash2023

Could you zip and share your model

Re: truss top member instable because of slenderness

Stephane.kapetanovic — Thu, 25 Sep 2025 10:15:25 GMT

hi @avadhprakash2023

in addition to the file requested by @Simau have you read this topic ? Modify Member Types

Best Regards

Re: truss top member instable because of slenderness

Simau — Thu, 25 Sep 2025 10:30:52 GMT

You need to add some horizontal and vertical bracing, then fil correct parameters for top members type

Re: truss top member instable because of slenderness

avadhprakash2023 — Thu, 25 Sep 2025 16:29:14 GMT

Here is the file. Can you please check that and also for the column in real world it is 2 member welded together but in robot i don't how to make the connection so i made 2 member and divided them into parts and connected that parts. So please also check that it is correct way or not.

Re: truss top member instable because of slenderness

Simau — Thu, 25 Sep 2025 18:38:09 GMT

Hi @avadhprakash2023

Before going any further on this topic, I have a few questions:

- Is this a real structure or a school project?

- Your first post was about the resistance of a split or merged member. Now you're asking other questions which need to be treated in another thread.

- You assigned the generic "beam" type to all the roof members, but in your model, it's very difficult to enter the buckling parameters because of the unusual design.

- Your structure will be unstable under wind direction Y

- I recommande you to post the model of a more classic structure to answer, initially, with the question of your first message