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RE: Light Gage Steel Design Programs

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We have used both the Pohill program and Prop86 by SureTie.  

- Pohill was much less expensive.  I think Prop86 was $495 and Pohill was
around $195 my apologies if these prices are not current.

- In the Pohill program you see the AISI formulas displayed with every run.
This is helpful if you are new to the AISI code.  Prop86 takes your input
and gives you answers.  The formulas and calculations can be viewed at your
option.  If you have a good understanding of the code the programs where you
put the right information in and get results out is a lot more usable.

- The Pohill program comes with the data base of light gage steel shapes
including MSMA shapes and Dietrich.  The Prop86 people charge for the shape
data bases (I think it was $95 per manufacturer).  I found this so annoying
that I had one of our drafters build the data bases we needed by hand when
she had breaks in drafing here and there.  It was probably a break even
proposition but I felt better.

- I found the Pohill program clumsy for doing combined loading, such as
studs, where we have an axial load plus a uniform bending load.  It required
us to go to a joist screen and generate the shears and moments and then
return to the axial screen.  If you did these in the wrong order the moments
and shears return to zero.

- I like programs that print out their results on a single page.  Prop86 can
do this.  With the Pohill program the best I could do was three pages - One
for section properties, one for combined axial and bending and one for
deflections.  Prop86 has a single page printout that shows Gross and net
properties, allowable loads and deflections. 

- Prop86 will print out joist and stud tables.  This has proved to be very
handy.

- Once you have your data base set up Prop86 allows you to configure your
members into back to back (I columns) or lip to lip (Box Columns).

Overall while the Pohill program will do the job we found that Prop86 would
do it quicker and gave us more concise reports.

*************

All light gage steel design requires you to make assmptions and choices
about design procedures.  I would like to throw out our default design
inputs and see if anyone has comments.

Steel Stud Design

1) Deflection Criteria - l/240
2) Design for net section rather than gross section.
3) We design all walls for full mechanical bracing.  We do not count on the
sheathing for bracing.  Our opinion is that many walls are heavily loaded
before sheathing is ever installed.  Also in a remodel situation sheathing
can be removed with no thought given to loss of stability of the wall.
4) All wall bracing is designed for lateral and torsional support so k*l for
torsion and k*l for bending are the same.  Typical bracing is straps on both
side of wall with a short section of track on each end.
5) In calculating kl/x for stud stability in the weak direction we always
use k=1. For a stud braced at the mid point or third points possibly a
smaller value of k would be justified.
6) We do not use the increase for cold-working.
7) We do not design for eccentricity unless we know that it exists.  No
accidental eccentricity is imposed.