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PostPosted: Wed Oct 08, 2014 4:46 pm 

Joined: Tue Sep 16, 2014 8:38 am
Posts: 1
Hello all,

I believe that my question is both a matter of general modeling, and a specific Sofistik question, so in case you are aware of the solution to it in a theoretical manner, but not in sofistik, I would be grateful to receive your help.

I am trying to run a nonlinear time history earthquake analysis of a building which is already modeled in Sofiplus 3D with QUAD elements (for shear walls) and BEAM elements (for beams and columns).

Fortunately, material nonlinearities are already implemented for quads and I simply have to type nmat yes when I run the time step analysis.

My problem is regarding the beam elements, that as far as I know are implemented only with linear elastic behaviour in Sofistik. I have been told that a trick would be to insert spring elements (that can be analyzed nonlinearly in sofistik) at each degree of freedom but this confuses me because I have no previous experience of nonlinear analyses and of using springs. I guess what they mean is that I should replace the geometric nodes with springs that have specific axial, flexural and shear stiffness (if I assume that due to the horizontal seismic loads the edges of the beams and the columns will yield first rather than the free spans, which is not totally wrong from an engineering point of view). At the moment the connection between the columns and the beams is rigid (option intersect with other elements is activated in Sofiplus). Or should I keep the nodes as they are and further add 3 springs along the 3 axes at each node?

Is this approach correct, or is there an easier and more correct way that I could do it? I would appreciate any help from you, because I have been trying to figure it out for long without success.

If you don't have time to reply specifically in my question I would appreciate if you could give me a hint of where I could find some theory or a similar example. I realize that maybe there is something already in tutorials and sonar but due to heavy work load with other dynamic analyses, I didn't have time to go in deep detail through them.

With best regards

PostPosted: Thu Jun 06, 2019 11:43 am 

Joined: Tue Jan 09, 2018 1:46 pm
Posts: 3
Hi did you find any solution to your question? I am also working on a similar problem and would love to know some hints/suggestions. Thank you.

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