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HSS to WF connection

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I'm designing a Warren truss enclosed pedestrian
bridge.  (Same one for which I asked about bearings
about a month ago.  Some projects move faster than
others.) The architect and I like 6 inch square HSS
for the diagonals (exposed inside), but I want to use
WF shapes (web vertical) for the chords, which aren't
exposed from the inside, because the floorbeam
connections and chord splices are simpler and the
bending between panel points is more manageable.

I can analyze the wideflange for web crippling , etc.,
for the diagonal in compression, and can probably
design that connection.  But how do I analyze the
tension connection?  In the AISC HSS Connections
Manual, the closest thing to this condition is the
welded Tee end.  They divide the force by the
perimeter of the HSS and size a weld; in other words,
the flange is implicitly stiff enough (or the weld
ductile enough) to not worry about how the force is
distributed over the width of the flange.  This seems
nuts.  I can imagine 2 inches of weld over the web of
the WF taking about 80 percent of the force, while the
flange tips bend and relieve themselves of most of the
load.  Since half the perimeter of the HSS is at the
flange tips, this worries me.  Do I just weld
stiffeners in under the flange, or is there a way to
analyze it more accurately?  Or should I use an HSS
chord like all the nice pictures in the manual?

I appreciate any help or advice.  Thanks.

Mike Hemstad, P.E.
TKDA
St. Paul, Minnesota

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