Cracked/Uncracked stiffness for Pushover

[draven]

Thanks for getting back to me so quickly!

At a previous post you mentioned :

Re: DBPH and FBPH
Post by seismosoft » 13 Jan 2026, 16:36

These differences are related to small differences in the initial stiffness between the two types of elements, DBPH and FBPH. Whereas in FBPH the stiffness is updated at each step of the analysis, in DBPH the moment-curvature curve is bilinearized and initial stiffness is kept until yield. The differences in the stiffness degradation is related to how inelasticity is modelled in each case, lumped plasticity vs. distributed plasticity.
Seismosoft Support

For FBPH If the stiffness is updated at every step of pushover i understand that the stiffness starts from the uncracked state and decreases. For DBPH if the stiffness is kept until yield, how can it start from the uncracked stiffness?

[seismosoft]

The elasto-plastic moment-curvature curve of the member in DBPH is created after section analysis and the bilinearization of the M-k curve. For more details, please study the details of the lumped plasticity model.
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