Not sure where your located so this link has methods for Europe and US.

Its about calculating the critical buckling moment.....Hope it helps.

https://engineering.stackexchange.com/questions/88/how-do-you-calculate-mcr-critical-buckling-moment

also, there's an existing question on ResearchGate that mentions the same problem

"How can I calculate the Mcr (elastic critical moment) for beams in abaqus?"

At this link :

https://www.researchgate.net/post/How-can-I-calculate-the-Mcr-elastic-critical-moment-for-beams-in-abaqus