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RE: Design of Steel Joists

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Kipp,

>From my experience, we do the joist design both ways.

1) If the loads are uniform loads and nothing special then we will design
the joist per the manufacturer's SJI tables.  Note that different
manufacturers may use different materials to make a specific joist and some
manufacturers list their own capacities in the tables listed.  Vulcraft is
one such example.  Refer to the logo at the bottom of the page to determine
if it is a SJI table of Vulcraft Table.

2) To my knowledge anytime a joist has special loads (i.e. concentrated,
tapered, or other non-uniform loads) it should be designed by the
manufacturer.  This is due to the fact that non-uniform loads may cause high
LOCAL loads in the diagonals or additional chord bending (stress) that won't
been seen under uniform loads.  These local loads could also could affect
the joint weld/connection designs.  The same should be done if special
deflection requirements are needed.

In the past I know that the following companies have designed and sealed
joist designs:
SMI Joist
Vulcraft
Canam Steel

Not sure which company you are dealing with but those listed above do have
the capacity to design and seal joist designs... be prepared to pay extra
for those services in most cases though.  Sometimes it just makes sense to
have them design and detail the joists because they can usually provide
lighter joists for the same loads (as compared to SJI Tables).

HTH
Greg Effland, P.E.

-----Original Message-----
From: Kipp.A.Martin(--nospam--at)mw.com [mailto:Kipp.A.Martin(--nospam--at)mw.com]
Sent: Wednesday, May 23, 2001 10:22 AM
To: seaint(--nospam--at)seaint.org
Subject: Design of Steel Joists


I will admit that it has been 3 or 4 years since I last design a project
that used open web steel joists, but I recently finished a job where they
were used.  I "designed" them as I always had done in the past.

   1.  Using design loads, I determined the loads on the joists and used
the SJI tables to choose a preliminary joist size.
   2.  I put this joist size on the framing plans.
   3.  I added notes to my drawings saying that the joist sizes were for
estimating only and that the joist manufacturer was to design the joist.
   4.  I provided the loads and deflection criteria for the joist design.
   5.  I stated that the joist design calcs must be stamped by a PE
licensed to practice in the state the project was located in.

Now that we are in construction, the joist mfr. is refusing to "design" the
joist  They will only provide calcs that show that the joist size indicated
on the framing plans meets the load capacity stated in the SJI tables.  I
asked a co-worker about this and he stated that he had never been able to
get a joist mfr. to do the design.  Has the standard practice changed that
much in such a short time?  I used steel joist on many projects in the
early and mid 90's and always presented the information described above.  I
never once had a joist mfr. refuse to provide design calcs and to pick the
joist.  What is standard practice now?

--Kipp Martin, S. E.\
  Portland, Oregon
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