RC BEAMS - Primary Beam / Secondary Beam Connection

[stroxy]

When I have a primary Beam Secondary Beam connection (as in attachment), Do I need to

1) uncheck the secondary beam as a support for the primary beam when transferring to the design module or can I leave both checked as supports!

2) What is the difference in the way the program interprets the 2 scenarios?

[Artur.Kosakowski]

The difference between marking or un-marking an adjoining beam as a support is in the way reinforcement is distributed (bending moments, shear etc. are taken from the results of calculations of a model in both cases).

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[stroxy]

Thanks Artur, I kind of figured that much. What I would like to know is whether the program would recognize the stiffer (primary) element in the connection when it is distributing bending moments and shears if both boxes are checked.

[Artur.Kosakowski]

No, there is no automatic detection which beam supports which yet the distribution of loads is based on real stiffness of both elements (the values of internal forces correspond to the real stiffness of both beams).

Please check: http://forums.autodesk.com/t5/Autodesk-Robot-Structural/Wish-List/m-p/3538438/

[stroxy]

OK I read (and if I understand you correctly) in the other discussion you pointed me to, that the main difference would be in the stirrup arrangement (and possibly bar curtailment and anchorage) since the internal forces are calculated based on real stiffnesses etc.  If so, then in that case I could leave both as supports so that my stirrups are spaced closer at the intersection (seismic disposition) and then probably manually extend the bottom bars over the intersection (if they have beem curtailed).  That way I should be almost always covered.

[Artur.Kosakowski · Accepted solution]

Correct. In case you also need stirrups on a width of such created support you can manually copy existing stirrups from its neighborhood.