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RE: Design of Steel Joists

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Foy,
What do you do on roofs for uplift?  I have seen very few roof applications
where at least the perimeter joists must be custom designed for a net
uplift.  Joists that have uplift are not in the tables.  For wind uplift
some of the webs fail (some web members are tension only), the standard
bottom chords are too light, and the bridging has to be modified to brace
the first bottom chord panel point.

The joists that are designed for uplift must be designed by the
manufacturer.  I require them to seal their work, and have not had a
problem.

Regards,
Harold O. Sprague

> -----Original Message-----
> From:	Foy, Warren [SMTP:Warren.Foy(--nospam--at)mhgrp.com]
> Sent:	Wednesday, May 23, 2001 11:53 AM
> To:	'seaint(--nospam--at)seaint.org'
> Subject:	RE: Design of Steel Joists
> 
> In the 13 years that I have been using joists for both floor and roof
> construction, I have always selected the joists to be shown on the
> drawings
> and that are expected to be used for construction.  I have never seen a
> set
> of drawings that require the joists to be selected by the joist
> manufacturer.  I use the term selected because the "design" of the joist
> (i.e. the actual sizes of the chord and web members) are the design of the
> joist manufacturer and must meet the requirements of the SJI.
> 
> The only exceptions to this are the occasions where non-parallel chord
> joists are used or where non-uniform joist loads are required.  In such
> cases, a schematic joist elevation is shown detailing the joist
> configuration and/or loads so that the selection and design can be
> performed
> by the joist manufacturer.
> 
>  
>  	Warren S. Foy
> Structural Design Manager
> The Mason & Hanger Group Inc.
>  
> 300 West Vine Street, Suite 1300
> Lexington, KY   40507-1814
> voice: 859.252.9980
> fax: 859.389.8870
> web: http://www.mhgrp.com 
> 
> 
> 
> 
> -----Original Message-----
> From: Kipp.A.Martin(--nospam--at)mw.com [mailto:Kipp.A.Martin(--nospam--at)mw.com]
> Sent: Wednesday, May 23, 2001 11:22 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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