The instability (3 type) in the RX direction in the node 54.

[Anonymous]

Hello!

I am creating 3d calculation model using Autodesk Robot Structural Analysis Professional 2015. Please find it in attached files. I have'nt finished it yet. When I am calculating it I am getting warning "The instability (3 type) in the RX direction in the node 54". Could someone please explain me where is the problem?

Thanks,

Atis

[Rafal.Gaweda]

Bars  2434 2450    2423 2444    2210 2260    109 1908     744 1904 1905     108 1900 1901     745 1896 1897      107 1893   should meet in common nodes.

Corrected file attached

[Anonymous]

Hello, Rafal!

Thank you!

So, if I understand right, there is some minimal distance between nodes at which Robot would like to join them?

Best regards,

Atis

[Rafal.Gaweda]

As a default is 1mm, not 1cm nor 5 cm.
Analysis \ Analysis Types \ Structure Model tab \ Tolerance....

In short - pay more attention for model accuracy in future.

[fenusn]

Hello Sir,

Could you please help ,me resolve the instability ERRORS I am having in my model? 

I have been learning ROBOT by myself for a while now, but I am getting frustrated by these instability warnings.

I am a very fast learner, and will appreciate if you can also point out what I did wrong.

Thanks

[fenusn]

There are just two floors in the ROBOT model attachment.

[Rafacascudo]

Too many releases. You don´t need moment releases on the end of bars that are attached to  pinned supports. Do you really need all those pinned columms on your model??

To correct  ,You can either turn all supports into Fixed ones or keep the pinned supports and delete the bar releases on the bars bottom end.

Very good to be a fast learner and you would be a lot faster if you learn to use the search button. There are literally at least 600 posts with this exact same question and with the exact same answer.

https://forums.autodesk.com/t5/forums/searchpage/tab/message?filter=location&q=instability&location=...

In many of them there is a standard recomendation on watching the excelent official support webinars by Artur and Rafal on Build your Robot Structural Analysis IQ - YouTube .

The "instabilities" one is number 16.

Watch it . And watch them all if you want to master RSA as quick as it can be.

[fenusn]

Hi Rafacascudo,

Many thanks for your prompts response... Very helpful.

Yes, I need all the columns pinned, cos the core wall {and shear wall(s) if necessary} is to take all lateral loads. Column sections will be excessive if fixed. Its better they are designed to take axial forces, and any minor moments resulting from eccentricities developed by lateral displacements. 

I ought not release at the pinned support, have corrected that and was able to resolve ALL the warnings, but one. The warning says 'The instability (3 type) in the direction RY direction in the node 84'. Please how do I resolve this single warning?

I am downloading ALL the videos right now, and will watch them meticulously immediately they are fully downloaded. I am also checking out previous queries and solutions. I won't mind if you can give me a head start, sir. No offence.

I am really enjoying ROBOT, awesome program!!!

Thanks again!!!

[Rafacascudo]

Read my answer here  https://forums.autodesk.com/t5/robot-structural-analysis-forum/instability-type-3-with-unidirectiona...

and apply the same test  to check if you can ignore the Instabilty type 3 warning

[fenusn]

Hi Rafacascudo,

Many thanks for the links and video. I was able to clear all the warnings. It's now running perfectly well without any instability warnings.

However, I have a few other quesions as regards wind load simulation. On that same model I sent you, the slab is quite irregular, and as such, drawing cladding with that profile is going to be a herculean task (almost impossible). Is it possible to simulate wind load without assigning cladding? I saw a video tutorial where the fellow simulated wind without assigning claddings

Many thanks... I sincerely appreciate your efforts here.

Franklin

[Rafacascudo]

Why don´t you try setting the claddings on  the plane of your columms ? Results ,probably, it will not be so different from those when in their real position.

[fenusn]

Hi Rafacascudo,

I did like you said. It really makes sense.

I have a challenge with regards to copying line loads to upper floors. I actually was able to copy to upper floors using load table and excel. On the floor of each level, I saw the loads copied, but on 3D view they aint showing.

Now, the main challenge is that these loads are not chased down. The reactions remained same, before and after copying.

Please, where could I have gone wrong?

Many thank you very much for your assistance.

[Rafacascudo]

Which line loads? on panel edge? , middle of panel? , on bars?

can you send the model?

[fenusn]

Hi Rafacascudo,

The line laod type is 'line load 2p', at the middle of the panel.

In the attached model, I already applied the line loads on ground and first floors, but need to copy same to all nine floors above.

Thank you for your time.

Franklin

[Artur.Kosakowski]

Hi @fenusn

This load type cannot be copied and have to be defined again between new points. What you can do instead is to define loads applied to lines and then copy these lines.

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[fenusn]

Hi Artur,

Thanks for your response.

I will do as you have advised, and get back to you accordingly.

Regards,

[fenusn]

Hello Artur,

Many thanks for your assistance so far.

Please, I'm doing a portal frame in ROBOT, and have modeled successfully without any warnings whatsoever.

The challenge I'm having right now is the excessive amount of deflection I'm getting after simulating wind on my structure.

Here's how I went about the wind simulation:
1. I computed my effective wind speed from spreadsheet based on all conditions stipulated by the code... Terrain, altitude, topography etc. It gave me 38. 48m/s
2. I input this value in the simulation and checked X & Y axes for wind load case generation. I didn't create wind profile.
3. After the simulation was done, I created all necessary combos ULS and SLS.
4. Ran a nonlinear analysis of load cases and combinations.
5. Checked my deformation at DL1+0.8Wx(-), DL1+0.8Wx(+), DL1+0.8Wy(-), DL1+0.8Wy(+).
I was having very high and excessive deflections. I know I shouldn't be having that.

My portal geometry is height to eaves 25.45m, multispan 24m each, 10 bays at approx. 7.5m.

Please kindly point out where I have gone wrong or what could be wrong.

Thanks again Artur.

[Artur.Kosakowski]

Hi @fenusn

First I'd try to determine which load case (alone) causes excessive deformations - is it one of the winds? Other? Or perhaps this happens for more than one?