Hand calculation of RC column's moment capacity

[Debasish Sen]

Dear concern,

I am a new user of Seismostruct software. I modeled a RC frame where the RC column has an estimated ultimate moment capacity, considering the axial load, of 41kN-m (as per Japanese standard). However, after pushover analysis of the RC frame I found that maximum moment generated at the base of column is about 31kN-m.
Could you please suggest me the theoretical approach (any code or reference) that Seismostuct follows to calculate moment capacity of RC column with axial load so that I can compute moment capacity by hand calculation.

Thanks in advance for your cordial help.

Regards
Dr. Debasish Sen

[huffte]

Capacity computed by a code or standard would not necessarily match that from a pushover analysis. However, the fact that your computed capacity, per code, is greater than the base moment from a pushover analysis, would seem to indicate that something is amiss in your pushover model. Or a possible computational error in the hand-calculated capacity.

I would recommend double-checking the model. Does your confined concrete model match that assumed in the hand calculations? Does the axial load from hand calculations match the windward or the leeward column in the pushover analysis? Did you re-compute moment capacities for both the windward and leeward columns, using axial loads from the pushover analysis? These are just a few things that come to mind as I try to determine what may have happened.

Best of luck with your work.

[Debasish Sen]

Thank you for your kind response.

I understand your points. I will check the model again.