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RE: Single Plate Connection of Collectors Procedure

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>I am analyzing some existing connections of
>W18 and larger collectors into columns.  They
>are one-sided plate connections with connection plate
>held by stiffeners on top and bottom similar to
>Fig. 10-25 on page 10-158 and Fig. 10-28 on page
>10-159 of the 3rd ed AISC LRFD manual.  The difference is
>that with my connections, there would be a large axial
>load in the beams as well as gravity loads.
>The design would need to take into account beam-end
>rotation like Table X in the old ASD 9th ed, but
>also account for the axial loads.  In addition,
>the governing limit state must be ductile because
>I am in Seismic Zone 4.

There are some alternatives here. You could connect the flanges and make the
beam moment connected. The axial force transfer is more compatible in that
approach. Alternatively, you could use a shear connection as others have
suggested and design it for the combined forces. Bearing deformations will
likely be all that is needed to accomodate the rotations while maintaining
the strength.

On the ductile limit state front, I think a ductile limit state must control
the system, but does not necessarily have to control the behavior of every
element in the system. That is, if you have an SCBF, the brace will be
configured to yield and/or buckle. The collector connection would then not
ever see more than the force in it associated with brace yielding and
buckling. The ductile failure mode requirement applies to the fuse element
in seismic systems. Other elements just need to be able to hang in through
the failure of the fuse, regardless of limit state controlling.

Charlie











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