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RE: CONNECTION DESIGN RESPONSIBILITY

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> I remember I read somewhere in this forum, that the design
responsibility
> of
> the connections in the US, is from the fabricator. Is this correct?

I'm amazed at the casual attitude that seems to be taken by so many
structural engineers with regards to their responsibility (or lack of
responsibility) for connection design.  

Has anyone ever done a study to determine the ratio between catastrophic
structural failures related to connection failures as compared to all
other failure modes combined?  I'll bet the ratio is over 10 to 1. 

I have no problem allowing detailers to select standard shear
connections based on reactions shown on the structural drawings, but
close attention has to be paid even to those "standard" connections.
What if you have a W12x19 roof beam framing in a skewed direction to a
W36x135 and what if the top of that W12 is raised 5" above the top of
the W36 because you have joists with 5" seats bearing on the W36 and the
W12 has to be flush with the underside of the roof deck?    The monster
cope on end of that skewed W12 will ruin all chances of using a standard
connection - not that this will prevent some detailers from trying. Most
detailers can select and detail standard shear connections, but most
will be unable to check the reduced shear capacity at the ends of beams
with monster copes - and severely skewed connections fall outside the
realm of most "standard" shear connection tables. 

For a structural engineer, the problem is that we don't know beforehand
whether a "connection savvy" fabricator will get the job or whether a
fabricator who is not "connection savvy" will be the low bidder.  In
recent years there's been another "player" in this equation - the
"connection savvy" fabricator who's read the book "The Contractor's
Guide to Change Orders".  This contractor will rain RFI's upon the SER
asking for "clarifications" about connections.  Anything that is outside
the realm of a "standard" connection will be a change order.  (Web
reinforcement for the cope? We didn't have web reinforcing plates in our
bid; we were going to use a 3 bolt shear plate.) The philosophy of these
fabricators is that they are selecting the connections from their
standard connection tables, but they are not responsible "designing"
unusual connections and they are not responsible for checking the
capacity of severely coped beams.

My opinion: Don't give short shrift to connection design. You'll find
out the hard way who's responsible for the design of connections if
something goes wrong with a connection on a project for which you were
the SER.

Clifford Schwinger




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