Hi every body
I have a steel frame with infrmFBH. i want to perform IDA ( Drift_max Vs Sa(T)--> spectral acceleration in fundamental period, following of this performance, I want to extract Sa(T) in collapse point. but the IDA curve doesn't have zero-slope and i don't really know what point is collapse point in this curve?
actually, the slope of curve are increasing instead of declining.[V]
thanks a lot
collapse in IDA
-
seismosoft
- Posts: 1316
- Joined: 06 Jul 2007, 04:55
Re: collapse in IDA
Hi Afakhimi,
With slip, you mean the slope of the curve?
SeismoSoft Suppoty
With slip, you mean the slope of the curve?
SeismoSoft Suppoty
Re: collapse in IDA
yes slope. sorry
he is my friend and working on same project.
he is my friend and working on same project.
Re: collapse in IDA
quote:Originally posted by seismosoft
Hi Afakhimi,
With slip, you mean the slope of the curve?
SeismoSoft Suppoty
yes, i am perplexed for this problem
Hi Afakhimi,
With slip, you mean the slope of the curve?
SeismoSoft Suppoty
yes, i am perplexed for this problem
Re: collapse in IDA
Hi afakhimi,
There may be many reasons for an IDA envelope curve not to feature a post-peak softening slope (the same may happen when running pushover analysis).
For instance, if your axial load level is relatively modest and your steel material features an ever-increasing hardening, then it may well happen that P-Delta effects will not kick-in and the structure will continue to "harden".
What one needs to do in such cases is to correct any modelling deficiencies (e.g. introduce a fracture strain for the steel, correct the axial load definition, etc) and/or define appropriate failure/collapse criteria (e.g. maximum interstorey drift, maximum chord rotation, etc) which will indicate when collapse occurs (independently of if the analysis continued to run or not).
Rui
There may be many reasons for an IDA envelope curve not to feature a post-peak softening slope (the same may happen when running pushover analysis).
For instance, if your axial load level is relatively modest and your steel material features an ever-increasing hardening, then it may well happen that P-Delta effects will not kick-in and the structure will continue to "harden".
What one needs to do in such cases is to correct any modelling deficiencies (e.g. introduce a fracture strain for the steel, correct the axial load definition, etc) and/or define appropriate failure/collapse criteria (e.g. maximum interstorey drift, maximum chord rotation, etc) which will indicate when collapse occurs (independently of if the analysis continued to run or not).
Rui