Beam Connection - Fixed or Pinned
Beam Connection - Fixed or Pinned
(OP)
We are debating this in the office. I am designing frame that will be constructed as shown on the attachment. My question relates to how to treat the connection. My coworker is saying to treat the connection between the perpendicular beams as a simple connection (ie no moment transferred to the bottom I-beam as a torsional moment), but my gut is telling me that this isn't conservative. I don't expect the top beam to develop a full fixed end moment at each end, but I expect there to be some moment capacity that then develops a torsion in the bottom beam. My reasoning for this is that if this connection detail were used for a cantilevered beam, anyone would assume full moment transfer to the bottom beam and design for torsion.
I realize that no connections are ever perfectly simple or fixed and that certain assumptions have to be made regarding moment capacity. Therefore, what is considered prudent in this situation? I could take a WAG and assume a percentage of FEM is resisted by the end connections.
I realize that no connections are ever perfectly simple or fixed and that certain assumptions have to be made regarding moment capacity. Therefore, what is considered prudent in this situation? I could take a WAG and assume a percentage of FEM is resisted by the end connections.






RE: Beam Connection - Fixed or Pinned
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Beam Connection - Fixed or Pinned
Pinned and don't worry about any torsion in the supporting beam.
RE: Beam Connection - Fixed or Pinned
another day in paradise, or is paradise one day closer ?
RE: Beam Connection - Fixed or Pinned
The cantilevered beam is infinitely stiffer to take moment in its strong axis direction than the top flange of the lower beam is to resisting the torsion. Seems like any imparted torsion would be quite small indeed.
RE: Beam Connection - Fixed or Pinned
Everyone else, thanks for the help. You all confirmed my hunch that this is normally disregarded. It's good to sometimes revisit fundamental questions like this to validate assumptions.
RE: Beam Connection - Fixed or Pinned
Dik
RE: Beam Connection - Fixed or Pinned
BA
RE: Beam Connection - Fixed or Pinned