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[SEAOC] Bracing Eccentricity

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There seems to be arguments on both sides and in-between on whether
the
eccentricity in a bolted brace connection should be considered and if
so
where.

Blodgett indicates that if the connection is "rigid" then the moment
from
the eccentricity should be used in the design of the member, if the
connection is "flexible" then the moment should be used to design the
connection (bolts and gusset plate) and ignored in the member.

"The Seismic Design Handbook", Van Nostrand Reinhold, seems to imply
the
same thing (assuming most brace connections are flexible) by saying,
"In
actuality, some eccentricity may occur due to the physical
limitations of
the connections, but this is usually ignored in the design of the
members.
However, any eccentricities in the connection must be considered in
the
design of the connecting bolts or weldments."

AISC Manual of Steel Construction, Volume II Connections, completely
ignores the eccentricity in both the connection and the member, even
in the
heavy truss section where the loads are significant and their example
uses
2 rows of bolts in one leg.

Rick's original question was what to do with a bracing member
utilizing a
Tee section turned so its flange is bolted flat to the gusset plate.
Probably the significance of this design is that the eccentricity is
out of
the plane of the gusset plane which could cause bending in the weak
axis of
the plate.

I suppose that if you adhere to the AISC design examples then you
could
ignore the eccentricity for the design in both the member and
connection
whether the eccentricity is in or out of the plane of the gusset
plate OR
that this eccentricity should be considered in the design of ALL
connections.

Does anyone else have any data, tests, reports, etc. to support
either of
these positions?

Thomas Hunt

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