Model Update: Nonconvergence Issue

[Kate_Rhoades]

Hello STKO team,

I have been working on a study of a building constructed to different US building codes during different years. I have had a lot of success with my 1976 UBC model, and it is running great! However, when I added two interior moment frames to represent the 1994 UBC (changed elastic sections and added joint parameters) I am having a nonconvergence issue. I have been trying to find a solution for the last couple of days, but have had no luck. I'm sure it is something small, like an element property or missing a defining step, as not even the static analysis will run, but I cannot find it. Would you be able to help me diagnose the problem?

I've attached the working 1976 nonlinear model, as well as the updated 1994 model.

Many thanks for your help,

Kate

[kesavapraba]

Hello, I find it challenging to identify the specific modifications made between the two models since your models are big. Could you please specify the changes exactly that you implemented? For instance, could you highlight the altered properties and their respective locations in the models?

[Kate_Rhoades]

Yes, I can do that. The attached images is of the 1994 model. The additions in this model are the moment frames circled in red at gridlines 4 and 6.

The names of the added elements all correspond to C2D-C8D, C2E-C8E, B2E-B8E, and B2F-B8F. Each of these elements has an elastic section, ModIMK for the plastic hinge rotation, and a zero length material for the hinge, and finally a special purpose hinged beam to combine all in the physical model. For the new joints, I have added joints 29-35 for the new moment frames. The joints utilize pinching 4 to represent shear failure, and a special purpose beam-column element at the joints.

Thank you for your help, please let me know if there are any other clarifications I can make,

-Kate

[kesavapraba]

Hi, I don't see the attached figures in your previous post. Can you please check if they are uploaded?

[Kate_Rhoades]

My apologies, I will upload them here:

1994 Moment Frame Additions.PNG (556.37 KiB) Viewed 3150 times

Please let me know if there is anything else I can help clarify

-Kate

[kesavapraba]

Hello, Kate. Could you please verify the dimensions applied to the columns and beams? In practice, they seem to be quite small, such as 30 mm x 24 mm for C2A column, for instance. You can double check the same for other geometry in your model. It would be useful to adhere to a consistent unit system and input the structural member dimensions and material properties accordingly.

[Kate_Rhoades]

Hello, thank you for getting back to me. My apologies for the units confusion. The building I am modeling in the US. All units are is in inches and lbs. I have double and triple checked and verified all of my material properties with hand calculations so I know they are correct, but probably why they look a bit unusual.

I am near certain that the issue I am having in the model is within the joints 29-35, since these are the joints added within the new moment frames. Maybe there is something I have not selected properly?

Thanks,

Kate

[kesavapraba]

Hello Kate. I reviewed the gravity displacement profile for the 1976 model first, and it doesn't seem fine to me. Could you please share the displacement profile (perspective - 3D) of the model at the end of the gravity analysis here? Also, I noticed that you've specified beam-column joint materials in the STKO preprocessor, but they are absent in the TCL input files. Thank you.