topic Re: Type 3 Instability in Robot Structural Analysis Forum

Type 3 Instability

muhammad_farhan256 — Wed, 29 Jan 2020 09:46:42 GMT

I'm working on multistory building, while calculation the warning appears, Type 3 instability at node 2560 in uz direction, i try to fix this using move by click it and merging to another point (I even unaware as I'm doing right or wrong), again calculations are performed but the Type 3 instability error occurred at another node, I repeated the same process of dragging and merging but Type 3 instability is occurring again and again on another node .
Type 3 instability at node 2560 uz

Type 3 instability at node 23360 uz

Type 3 instability at node 72868 ux

Type 3 instability at node 15240 uz

Help me, it would be appreciated if you make a video clip how to fix these instabilities .
Thanks in advance.

Re: Type 3 Instability

Rafacascudo — Wed, 29 Jan 2020 11:17:20 GMT

Searching the forum gives https://forums.autodesk.com/t5/forums/searchpage/tab/message?advanced=false&allow_punctuation=false&filter=location&location=forum-board:351&q=Type%203%20Instability%20

Official Webinar 16 about instabilities on Build your Robot Structural Analysis IQ - YouTube

https://www.youtube.com/watch?v=5CCLzG12JQ4&list=PLY-ggSrSwbZqow_60fiqJwS69mg1nQMzk&index=17&t=35s

Re: Type 3 Instability

muhammad_farhan256 — Wed, 29 Jan 2020 11:42:14 GMT

I've gone through the post availble on forums and seen the webinar already regarding instabilities and solutions, but the proposed solutions aren't working or might be complex for me get solutions, a video clip could help me.

Re: Type 3 Instability

Rafacascudo — Wed, 29 Jan 2020 12:43:29 GMT

Zip and attach your model

Re: Type 3 Instability

muhammad_farhan256 — Wed, 29 Jan 2020 18:28:16 GMT

Glad you asked but I'm working in office, and unfortunately I can not share the model, its against our office policy.

could you help me in any other possible way? Please make a video clip showing how to fix type 3 instabilities.
Thanks.

Re: Type 3 Instability

muhammad_farhan256 — Thu, 30 Jan 2020 06:49:30 GMT

I've attached the zip file, kindly guide me how you will be fixing these error, suggest me via screenshots and videos. Thanks in advance.

Re: Type 3 Instability

Rafacascudo — Thu, 30 Jan 2020 13:35:52 GMT

Instabilities type 3 can be ignored if nodal displacements are compatible with structure size. Seems to be your case.

Warning was given probably to a large discrepance between members of stiffness matrix

Re: Type 3 Instability

muhammad_farhan256 — Thu, 30 Jan 2020 20:29:20 GMT

I have to perform Modal Analysis, as far as i know instabilities in model doesn't execute seismic analysis unless all the errors have been resolved.

I've watched and used skyline in structure analysis, as prescribed in Instability warnings during model analysis Webinar in, 55:15 to 01:00:05 , I'm exactly facing the same instability warning which is transferred to another node again and again. Moreover I'm not able to fix this warning Elements not assigned to any story.
Suggest me some fixes (Meshing Recommendation, Nodes Releases, Element assigning to story etc ) via video clip.
Many thanks for thinking over my issues,looking forward for the solutions.

Re: Type 3 Instability

gustavo_c_vasconcellos — Fri, 31 Jan 2020 21:47:59 GMT

I agree with Rafacascudo,

This type o instability is typically the result of large differences in the element stiffnesses.

Sometimes this difference is due to very short members (usually nodes that are too close)

Gustavo