Robot Steel Frame analysis

[athi_uk985568]

Hi,
Recently I have done a steel frame analysis in Robot 2011 and Can you please answer the following questions:
1. what is the default connections in Robot among the beams or beams and columns in a 3D frame?
2. Is it a rigid or pinned connection?
3. If I apply a pinned-pinned release among the bars structure becomes unstable during the calculation, how can I solve this issue?
4. Do we need to apply pinned-pinned releases among the bars when we do a frame analysis?

Many thanks

Regards,
James

[marcin.rakus]

1 and 2 - by default it is rigid connection (release label has to be applied to get pinned model)
3. maybe to much direction released? 'torsional' direction (for MX) should be released only with one bar end. check status of releases of adjacent elements.
4. I believe that depends mostly what model is assumed.