topic Re: Non convergence of non linear problem in Robot Structural Analysis Forum

Non convergence of non linear problem

formosa.darrell4 — Fri, 08 Apr 2022 07:19:17 GMT

Hi,

I am a Structural Engineering university student, and our design project is to design a Cable stayed bridge. I am modeling the bridge on Robot and once i set the cable members as cables the program gives me the error of Non-convergence of non linear problem, this is with the Super imposed dead load and when I set a moving load. Ive tried to change the setting as per the Autodesk solutions but none seem to work. Does anyone know what the problem might be?
I have attached the robot file below.

thanks

Darrell

Re: Non convergence of non linear problem

Krzysztof_Wasik — Fri, 08 Apr 2022 20:10:01 GMT

Hi @formosa.darrell4

You have used incorrect format for model saving. Use RTD format (not STP)

Re: Non convergence of non linear problem

formosa.darrell4 — Sat, 09 Apr 2022 06:52:37 GMT

for some reason it does not allow me to upload the .rtd file

Re: Non convergence of non linear problem

Romanich — Sat, 09 Apr 2022 08:21:01 GMT

Hi @formosa.darrell4 ,

Zip the model first or if the size of the model is big use WeTransfer for example.

Re: Non convergence of non linear problem

formosa.darrell4 — Sat, 09 Apr 2022 08:22:20 GMT

this is it

Re: Non convergence of non linear problem

Krzysztof_Wasik — Sat, 09 Apr 2022 09:31:33 GMT

Hi @formosa.darrell4

It seems that cable initial forces proportion is not correct (cannot be balanced in the model)

Increase force in cable 300 mm to 210 kN

Activate Matrix update after each iteration (for each load case)

Re: Non convergence of non linear problem

Stephane.kapetanovic — Sat, 09 Apr 2022 10:03:34 GMT

Hi @formosa.darrell4

Two small things. The bridge deck does not have a correctly defined section (Ax, Ay, Ix null), use the section creation tool for this. You must also remove the self weight of the cables by limiting the elements to a part of the structure equal to the bars 19A23 only because the cables do not have to be loaded.

Best regards