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Re: steel costs

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"Andrew D. Kester" wrote:

> I have browsed through the AISC tips on economics, but some of them are a
> bit old and I was just wondering if the following rules of thumb still apply
> and if people agree:
>
> -Avoid stiffeners as much as possible, extra fabrication and welding. An
> increase in the size to avoid them is worth the cost of the steel.

Yes

> -If I have a small project with say, 10 steel beams or less, I should try to
> use the same shape whether it is way more then required or not. This way a
> fabricator can pull one shape of steel and cut from it several pieces rather
> then several. Also this will make doing connections easier and more uniform,
> and avoid field confusion.

Yes

> -Avoid all around welds when not needed by design. Go with a 3" weld top and
> bottom for instance instead of 6" on all four sides... This would especially
> apply to columns with small uplift forces. (Our typical details always show
> a weld all around on a TS to BP connection.)

Yes

> -Try to use bearing bolt connections vs SC.

Yes

> -How much more is an in-field web connection vs bolt (%)?
>
> -Are tube steels any more then W shapes per pound? I like them a lot because
> they are good in biaxial and torsion, and good as axial braces.

HSS sections have an increased material cost but the reduced labor charge for
connections (especially on W6 and W8 columns) will make them cost effective.
They also have a smaller surface area for painting or fireproofing coverage.

> -Would a slotted connection with a plate in the middle of a TS be cheaper
> then one plate on each side? I am guessing the two plate connection would be
> cheaper so they do not have to slot the TS...

Slots in an HSS are expensive compared to a properly designed weld.

> Any other tips or rules of thumbs that you don't think are in the AISC info,
> feel free to mention. I think some of the things we have been doing may be a
> "standard practice" thing that may be a a bit too conservative and result in
> unnecessary costs. Also, sometimes it makes no difference which way we do it
> for us, but to the fabricator it makes a huge difference. I would like to
> save the client money and avoid field problems as much as possible without
> design integrity compromise..

Andrew:

You need to attend the latest AISC seminar on Practical Steel Design: 2 to 20
stories.
The first lecture on steel economy will answer a lot of these questions in
detail.

--
Davis G. Parsons II, PE RA AEI
a practical architectural engineer
in Fort Worth, Texas



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