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Re: Plastic moment capacity of concrete filled steel pipe

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In a message dated 98-03-17 23:26:57 EST, Bruno Cotes writes:

<< I don't think you need studs for a concrete filled pipe.
 
 This is different than a composite steel girder with concrete slab on
 top. When the girder deflects, there is a very small relative movement
 between the girder and the slab. This movement engages the stud. Once
 the stud engaged, the composite action develops.
 
 For the case of a pipe filled with concrete, I can't imagine the
 relative movement between the concrete and the pipe happening. This is
 due to the confinement of the concrete inside the pipe. The composite
 action develops without the studs.If you had studs, I don't think they
 would be engaged at all.
 
 The same principle applies when steel girders are encased in a concrete
 slab. I am aware of old structures designed according to this principle
 which are still standing.
 
 Bruno Côté
 BOCTE(--nospam--at)ibm.net >>

Thank you Bruno for your response.  I understand your reasoning.  However,
would shrinkage of concrete make any difference?  Many old structures where
steel beams were encased in concrete have reinforcing around steel girder
which makes it more monolith (in my opinion).  In the case I am reviewing,
there is no reinforcement inside the pipe.

I wonder if there is any test data or established procedures / criteria for 
such applications?  Does Caltrans or any other industry use combined capacity?


Anand Nene, S. E.