Dear Experts,

I have a specific inquiry regarding a feature in SAP2000.

I am particularly interested in understanding more about this article:

Center of rigidity - ETABS - Computers and Structures, Inc. - Technical Knowledge Base (csiamerica.com). I tried to extract the said center CR using SAP2000 by following the same procedure, but the results were not as I expected. My questions about this matter are as follows:

1- Regarding this equation: XCR = – Rzy / Rzz, how can the division of two rotations produce a length?

2- How can the software take into account the mass source (in the case where a portion of loads are taken into consideration) if I extract the rotations of the unit load cases?

3- I am using the OAPI of SAP2000. Is there any other approach you know that can directly excerpt the CM and CR?

Your guidance on this matter would be immensely valuable to me.

I appreciate your time and consideration and look forward to your positive response.