semi rigid connection

[varafkhami]

Hello
I need to modeling semi rigid connection in portal steel frames(E.Bayo modeling of semi rigid connection or cruciform element)in opensees to pushover analysis.
Thanks

[fmk]

well the only way to do it is at duplicate nodes at a joint and a rotational spring to model the semi-rigid connection. you can either constrain the translational dof or have springs here as well. do note that your periods are going to change. i suggest you play with a portal frame and the effect on periods before you go big.

[Halim]

Thanks,
that solved my problem same as stated in above

[varafkhami]

Hi ;
I have a 12X12 stiffness matrix for each 2d frame connections;how can I add new element with this stiffness matrix to being assembled with other element;
Thank you very much.

[fmk]

if the dof at the element nodes match the other elements framing into the node you need to do nothing .. if they are different you need to create duplicate nodes and tie the nodes together with the equalDOF command.

[varafkhami]

in each connection nodes have 3 dofs match to other element nodes, but stiffness matrix for this element is different from other element.how can apply this matrix ?
thanks.

[fmk]

how is it different!!!

[varafkhami]

In this method we replace beam to column connection by a cruciform element that 4 nodes exist in corner of this element(this element has dimention in X and Y direction).when this connection is semi rigid we have a 12x12 stiffness matrix for this element according to 4 nodes (and 3 dofs in each nodes);now how can apply this matrix to define new element for connections ...
thanks a lot.