I think you mean providing force releases in beams and columns? am i correct.
I think you mean for example a simply supported beam on a structural plan, or the end of a continuous beam if it was end hinge.
My opinion is that isn't a rule of thumb it is a modeling idealization , you may not do that ,but you also have to consider the hogging moment into your design ( RFT if RC beams or LTB of lower flange if Flanged steel beam). About the reason of realising i think that we consider a knife end support and this is theoretical deem. the width of the supporting column is the reason behind the hogging moment at end support.
In real structure, there is no perfectly pinned or fixed beam end connections. The release parameter in Staad Beam Spec is used to apply the designers assumption and intention on how the beam model will be connected to the supports. For example, if you want to connect an intermediate beam to the main girders, you may need to assign releases (MZ or MY) to the ends to prevent the main beam from carrying huge torsion because of the end moments of the intermediate beam. After making such assumptions, you need to properly detail the members (as per Batman07's advice) so that the real structure would behave similar with the model.
I think also that the connection between beam and column must be fixed, and between girder and beam should to be pinned, because that's how the connection work in the real model. Also it is all about the hysteresis curve of the real connection, so that doing that analysis you can assume which type of the connection is moment resistant or pinned.
Just to add and elaborate; In STAAD, there are 2 coordinate systems i.e: global & local. The 'release' command is meant for local coordinate of a member. If you want to see the orientation of the members, you can activate the graphical presentation of the members and so you will have an idea on how the forces and moments will direct to. But be careful, if the model is not correct the presented graphical member orientation will be erroneous either. Cheers. .
Answered by
Haseeb Jamal
at
Aug 6, 2010 12:35 PM
