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RE: Steel Moment Frame - Channel to TS Colum

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> As I read 2213.6 for Ordinary Moment frames, PR joints must be tested, 
> 2213.6.3.2.  If they are tested and they perform like PR joints than they
> can 
> be deseigned as PR joints.
> 
> Since no one will want to pay the money to test these joints, the real 
> question is can the joints that you describe be declop the strength of the
> 
> girders. I suppose it is possible, but without specific loads and sized it
> is 
> hard to know
> 
> 
> 
Undoubtedly, PR joints may produce different structural response. That may
be a hidden cause to structural failure. The structural analysis methods (we
learn at college) have a big hole that simply makes an assumption of perfect
rigid joints, but never checks if the assumption is valid. If the assumption
is invalid, how to analyze structures? The fact is that, in most actual
structures, the assumption of perfect rigid joints is invalid. Based on this
fact, the traditional method for structural analysis is not totally safe to
design actual structures. Partially rigid analysis is a better solution, but
is too new.



If you like to see how much difference may produce, the following is an
example for shearing connector.

connector              connector   
strength                   load  (shear)       
========================
perfect(100%)          5004.259
99.9999%               5004.257
90%                       4869.606


It is near impossible to design a perfect rigid joint. By examining
connector dimension in some examples, most joints in actual structures have
a strength between 90% and 98%. The difference in shear force between 100%
and 90% of perfect rigidity is about 130lbs. This difference in shear force
also make a difference in internal moment as (130xD) where D is the distance
from the joint.