Seismosoft | Earthquake Engineering Solutions

I am a new user of Seismostruct and i modeled a simple structure (a two column fixed based frame) in order to understand how the program works.

I modeled a bilinear link at the upper end of a column to approach a concentrated plasticity, i.e a non-linear hinge, (all members are elastic) and tried to observe the non linear behavior of it after applying a lateral force incrementally (static push over).

Perhaps I didn't model the non-linear link properly, but shouldn't the values of the moment and the chord rotation at the end of the column correspond to the values of the non-linear curve through which the bilinear link is modeled? (the "rotation" at the one axis of the link response curve corresponds to the chord rotation at that end of the member isn't it?) Instead of that the "hysteretic curves" has zero values.

Thank you.

(Do you think it is possible to send the .spf file?).

Finally, I don’t think that I’ve made a mistake in modeling the non linear link.
Maybe that what I observed, i.e. the incoherence between element’s values at the considered point (moment and chord rotation) and the corresponding values of link’s response curve, has to do with the need of calibration of the elastic element properties in order to render them compatible with the link element (that is mentioned in the topic named “How to model concentrated hinges” in 03-Analytical/ modeling capabilities)?

Any kind of help is welcome!

TUC, if I understand your model correctly, the rotation at the end of the column will be determined by the elastic properties of the elements, the pre and post-yield stiffness of the link, and the relative values among these parameters.

The moment and rotation in the link, however should be as you say. So make certain:

1. that you are plotting hysteretic curves for the link itself, not curves for chord rotatio at the end of a beam or column
2. that the loads are, in fact, sufficient to yield the links
3. check your units

Best of luck TUC.

Thank you for the reply,

I will consider your suggestions.

TUC, I looked over your model and made some changes to get the link participating in carrying the load. In essence, you originally had the end of the beam connected to the top of the column, with the link being external and thus, seeing no load.

The link needs to be "between" the top of the column and the end of the beam. So the top of column node is attached to node 1 of the hinge and the end of the beam is attached to node 2 (originally coincident with node 1) of the hinge.

I hope this helps and wish you success in your project TUC.