strange hysteretic curves

[chiaramgn]

Dear seismo,
trying to do a dynamic analysis on a multispan srch brigdes in reinforced concrete I noted some strange behaviour in the hysteretic curves.
I used an accelerogram defined with 0.01 sec time history and i used steps of 0.005 for the analysis. The accelerogram is defined for 14 sec lenght. The model runs good but I don't understand why these strange hysteretic curves. I did also with 0.0025 steps duration but seems to be also worst. I will attached a picture of the curves,
https://www.dropbox.com/sh/u7plj3cwod41 ... D0xva?dl=0
Thanks,
Chiara

[seismosoft]

Hi Chiara,

The curves do not seems unreasonable. The nice smooth hysteretic curves that you expected can be derived only in small models (e.g. simple laboratory tests).

Seismosoft Support

[ruipinho]

Chiara,

I second the comment by Seismosoft Support; higher modes will lead to the type of hysteretic response curves that you obtained, which do look pretty normal to me.

Rui

[chiaramgn]

Thanks to everybody, Chiara

[chiaramgn]

I've another problem. I did pushover analysis in the X direction and dynamic analysis. Increasing the accelerogram to searching IDAs curve what I noted is that the curve doesn't follow the pushover one but it is more or less elastic also for base shear really higher than the capability given by pushover.Have you any suggestions or idea of the reason?