How can I analytically connect overlapping structural members?

[efaustoD3RAG]

Hello, I am trying to run structural analyses by building the structure/analytical model in Revit and exporting it into Robot. I have overlapping brace/slanted column members that need to be connected, but Revit and Robot seem to treat them as if they are unconnected.

Revit 3D View

 Revit Analytical Model

When members are connected they seem to form a node, but there is no node where I need a connection (on the X). It seems to only want to make a connection/node when members intersect at one of their endpoints.

Robot Structural Analysis.  Viewing the S Max does not give an expected result if the diagonal members are actually connected. I've tried placing structural connections (direct bolt), but that doesn't seem to make a difference.

Thanks in advance for any help or ideas!

 

[RPTHOMAS108 · Accepted solution]

You would probably need to break the members in Revit or add a node in Robot to join them there.

Typically one is strut and one is tie isn't it, so wondering why this common detail exists with the connection there. The connection at crossing position could perhaps be argued as providing restraint to strut via a taut tie member to reduce effective length of strut. Probably most would not argue that and it may not be justified in your regional code (easier to assume no restraint there). Probably would not be classified as an independent restraint (if that is part of the requirement for one).

Shouldn't you have the ends of the bracing pinned so you would have a uniform stress distribution along members? Not sure what Robot is showing there, seems you are putting the bracing in bending with fixed ends.

[efaustoD3RAG]

Thank you for your answer - adding a node in Robot worked. 

"Shouldn't you have the ends of the bracing pinned so you would have a uniform stress distribution along members?"

Not sure what you mean by this - aren't members automatically pinned/fixed when connected at a node?

[RPTHOMAS108]

You have to check in Revit what the ends of analytical stick members are set to, looks like it is exported 'Fixed' by default. Regarding end fixity Robot follows what happens in most analysis programs: fixed ends are assumed and end releases are additional data to be added.

Can also add joint releases in Robot.