As far as I am aware there is no commercial software at present for progressive collapse, just research. Also progressive collapse is more a qualitative issue than quantitative.
Any frame analysis software with a programmable interface would be helpful for the analysis. Without the programmable interface simply copy the model, delete the members and change the loads. With a programmable interface automatically delete members and change loads using the one model, and search for the critical condition.
Regards
B.Tech (mfg & mech), MIIE, gradTIEAust
mailto:sch.tectonic@bigpond.com