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Dear seismo,
I was working with a big brigde in cls and doing incremental dynamic analysis I had big differences with the pushovers results.
So I tried to do the same type of analysis but on a single pier of the bridge.I did pushover in X direction and after With the same accelerogram that I'm using for the big structure I did incremental dynamic analysis, but after the first elestic phase with dynamic analysis I have different results, going really higher with the capability of the pillar. The damping for the dynamic analysis is set as Rayleigh mode with the first two mode obtaine by eingevalues analysis. Why you think that the results are so far?
Thanks, Chiara
I attached the link of the curves obratined and the model too.
In the curves, the results are expressed as shear/self-weight ratio and displacements (in millimeters).
https://www.dropbox.com/sh/u7plj3cwod41 ... D0xva?dl=0

Chiara, this matter is discussed in a recent post:

http://www.seismosoft.com/forum/topic.asp?TOPIC_ID=1882


Rui

actually the problem is a little be different. I don't have problem with dynamic analysis but with the comparison with pushover!

I am not sure if I totally understood your point, but discrepancies between pushover results and dynamic analyses has already been cited in the past.

Static pushover analysis (SPA) lacks a rigorous theoretical foundation since the nonlinear response of a structure is assumed to be related to the response of an equivalent single-degree-of-freedom system [Ref 1]. SPA is based on the incorrect assumption that the distribution over the height of the structure of the equivalent lateral forces remains constant during the entire duration of the structural response. Thus, it neglects duration and cyclic/hysteresis effects, and the progressive changes in the system dynamic properties (i.e., nonlinear structural behavior is load-path dependent, and the deformation demands depend on ground motion characteristics).
The inherent inability of SPA to correctly determine the seismic demands, specifically for structures that deform far into their inelastic range of behavior has been clearly documented in many studies [Ref 2 for example]. Adaptive pushover analysis which is also incorporated in SStruct is toward this end.

Hence, what you observed comparing dynamic results of one EQ record with pushover is not something unexpected. Hope this helps!

[Ref 1] Villaverde, R. (2007). Methods to assess the seismic collapse capacity of building structures: State of the art. Journal of Structural Engineering, 133(1), 57-66.

[Ref 2] Chopra, A.K., and Goel, R.K. (2002). “A modal pushover analysis procedure for estimating seismic demands for buildings”. Earthquake Engineering and Structural Dynamics, 31(3): 561–582.

quote:Originally posted by chiaramgn

actually the problem is a little be different. I don't have problem with dynamic analysis but with the comparison with pushover!

Chiara,

I reconfirm that the differences that you are reporting between the results of static and dynamic analyses may be due to the issues discussed in the post I refer to, as discussed in the paper I mention there.

They may also originate elsewhere, of course.

Rui