Pinned Connections

dobi3 · Post by **dobi3** » Thu Feb 26, 2009 8:49 am

Dear all,

Do you know where in the manual I can find a description on how to model pinned connections? I know the "fix" command would work if I am applying boundary conditions, but how do I model beam-to-column pinned connection?

Thank you very much!

silvia · Post by **silvia** » Thu Feb 26, 2009 9:12 am

you have to put two nodes at the same location, one for the beam, one for the joint and use the equal dof to connect the pinning dofs.
if you want to put in a flexible connection, this is where you would put a zero-length element in that dof.

dobi3 · Post by **dobi3** » Thu Feb 26, 2009 1:16 pm

Dr. Silvia,

I tried your suggestion and I also tried defining a semi-rigid connection with zero stiffness. Both runs give me the same results. However, when I run the same frame on SAP 2000, the results differ by up to 7%.

Do you think I have a problem in either SAP or OpenSees models, or this is a reasonable error range?

I am only running a 1-story, 1-bay frame with uniform gravity load and lateral point load.

Thank you for your help!

silvia · Post by **silvia** » Thu Feb 26, 2009 2:57 pm

the different programs, likely, handle axial stiffnesses differently.

dobi3 · Post by **dobi3** » Fri Feb 27, 2009 8:22 am

OK. Thank you. I really appreciate your help!