Link gap-hook definition

[Abdallah_Magdy]

This is Abdallah Magdy, a graduate student in the structural engineering department – Cairo University, and studying the effect of torsional pounding on colliding buildings. First of all, thank you for providing us with a free academic license of your finite element software “SeismoStruct version 2018 release 2). In order to model the pounding between the two buildings, I use link-gap hook element but I get not logical results as follow:
I modeled a cantilever beam connecting between nodes 1 (fixed) and node 2 (free). Then I created a link-gap hook between node 2 and 3, which has the same coordinates. After that, I applied a unit force on node 3 to see the axial force in the cantilever (see the attached example). The load is a two cycles sin-wave, while the displacement d (+) is taken 10 meters and displacement d (-ve) equal zero. As such, I expect the cantilever should experience two-half cycles similar to the compression segment of the load, while the tension should not be obtained. The same is expected to be obtained in the spring. However, the cantilever experienced both tension and compression while the spring force equals zero all the time.
I believe there is a mistake, may be in my definition of the link-gap element. Could you please help me in solving this problem? You can download the file from this link
https://www.mediafire.com/folder/11ipgr9hxijza/

[rbsce.ph]

Hi Seismosoft,

I tried modelling a 2D RC frame with infill panels with gap links at the upper part of the wall. However, when i tried defining the gap link for one corner of the wall, it keeps on saying that Nodes 1 & 2 should coincide intially (my 2 nodes have the same coordinates), but works fine for the other corners of the infill panel. Can you please help me in solving this? Your comment will be highly appreciated.

Thank you and regards,

[z.gronti]

Dear rbsce.ph,

If you have not created the coincident nodes from within SeismoStruct, i.e.you might have pasted them from an excel file, the existence of decimals, that might not be visible when checking the coordinates from within SeismoStruct, might be possible. Hence, I would advise to delete the nodes and create new ones from within SeismoStruct.

[rbsce.ph]

I created a 16mm gap between the upper beam to wall and another gap for column to wall. I was able to define a link (gap-hook) for coincidental nodes N and N*, M and M*, I and I*. However, when I am defining the link for J and J* it keeps on saying that nodes 1 & 2 should coincide initially as described in IMAGE1.

Your response will be highly appreciated.

Thank you,

[seismosoft]

When defining a link element, the two structural nodes shuld initially coincide. If you want to create a link between two non-coincident nodes, you may define three nodes, the two of which are coincident. You may connect the two coincident nodes with the link element, whereas the third node may be connected with one of the two link nodes with a rigid link.
Seismosoft Support

[rbsce.ph]

Yes, I did create 3 nodes, NODE J and NODE J* for the gap-hook link and then I will define a rigid link for NODE 2 and NODE J*. However, I can't define a link for J and J* as it keeps on saying that they should be coincidental. I don't know what seems to be the problem since both nodes have the same coordinates yet I can't still create the link. Please help.

Thank you.

[seismosoft]

If you created the nodes coordinates with Excel, some round-off errors may have occured. If you edit the J and J* from inside SeismoStruct, the coordinates should be considered correctly by the program.
Seismosoft Support