How to obtain the ultimate bending moment

[Dzonni]

Hello, everybody. I have conducted the lateral-torsional buckling analysis of a channel section beam. I have obtained the critical moment of lateral-torsional buckling and now i want to obtain the ultimate moment capacity, which, when the initial imperfections are included, should be less then the critical moment. I have used the Riks method, with the applied load which is equal to critical load and i have assigned the stopping criteria as LPF=1. When the analysis stops, what should i do in order to obtain the moment capacity? Do i look for section forces? Do i integrate the stresses? Any help will be of great value.