Hi, I am trying to model a X-braced frame with Frame members as beam elements and X diagonal braces as truss elements. I could get the results. But now I want to model the four corners of frame as pinned connection. The supports are pinned at both column ground locations. I am applying a lateral load. I tried with *RELEASE keyword to release the moments at the beam column joints but I am getting the following error. 

An invalid element end identifier 0 has been specified on the element

A release has been specified on element 0 but this element has not been defined

I also tried using connector section - coincident builder -> Connector section -> Basic -> Translation -> joint at four corner vertices. To do that I have modelled the frame alone as part-1 and frame + X brace as part-2. Now in assembly I am trying the merge/cut option so that (Frame + X brace) - (Frame) will give me X brace as separate part. But when I am trying to do that I am getting the following error :

"cut operation failed because the base instance was not modified ". I don't know the reason.

Please kindly help with with these options or kindly suggest some other option for modelling pinned connection at 4 corners.