Seismosoft | Earthquake Engineering Solutions

could you please help me model a concrete frame attached to it steel frame from inside (internal frame),
in other words, I have an existing RC frame and I need to add a steel frame to it ?

Dear Mina Rizkalla,

There is a number of composite sections available in SeismoStruct. Does any of them cover your modelling requirements? Because I am not sure that I understand what you want to model.

can I attach a picture here to illustrate what I want to model ?

Dear Mina Rizkalla,

You may model composite sections by inserting more than one elements to the same nodes with the use of rigid offset lengths or, in case you use different nodes, you may use rigid links to connect the two members. If you feel that the rigid links at the two ends are not enough, you could subdivide the member in 4-5 segments, employ the infrmDB element type and connect both the member ends and the mid-nodes with rigid links.

How can I add a material type/curve (Popovics and Karsan-Jirsa concrete stress-strain curve model) ?

Dear Mina Rizkalla,

Users are not able to introduce any material type/curve in SeismoStruct.

Instead of the rather simplistc Popovics and Karsan-Jirsa model, you could use the much more advanced and accurate con_ma Mander model in SeismoStruct.
Seismosoft Support

I tried both solutions, the rigid offsets and the different nodes.
The rigid offset, didn't work well or give good results, the other solution which was using different nodes was pretty good and gave acceptable results.