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# Fixed and free pinned beams at the same node

## Fixed and free pinned beams at the same node

(OP)
How can I specify the situation below?
Let's say there are 4 pinned beams that meet at the same node, say, beams 1, 2, 3, and 4.
Let's say beams 1 and 2 are fixed in relation to each other, so are beams 3 and 4 between themselves, but the first pair is free to rotate in relation to the second.

### RE: Fixed and free pinned beams at the same node

You can't do what you suggest in a direct sense because the pinned scheme in CADRE specifies the fixity of the beam to the node (not to any other element.  When two beams are 'fixed' to the same node then they are then fixed together.  One indirect means of accomplishing your scissor type action is to fix beams 1 and 2 to the node (as you suggested).  The others (3 and 4 should be pinned to the node.  Now, to get 3 and 4 to fix to each other you can to build another beam that runs across the node from new nodes that you create on beams 3 and 4 near the original node.  That beam should be fixed at all ends.  The short stub beams on the end of beam 3 and 4 that connect to the original node should be fixed on the beam end and pinned on the original node end.  This will work in most cases but you have to be careful not to make the stub beams too short or numerical accuracy can affect the results.  Its best to first build a simple model for which you can calculate the answers, then test your sizing and modeling technique before moving to the actual model.

### RE: Fixed and free pinned beams at the same node

If you (or any forum member) would like a sample CADRE model with detailed explanation just send me an email to support@cadreanalytic.com

James

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