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RE: Pre-Eng. Steel Bldg Moment Ftg.w/ Tie-Rods;& Base PL. Shear

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Yes, we figured that good one out when we did a hockey rink (actually, the contractor suggested it).  We wanted to do that here, but the manufacturer was not willing.  

It's one of those outfits that advertises "surplus" Wal-Mart buildings at a "discount."  The owner was sucked into it and couldn't get out.  The contractor says it was no discount for her compared to a Nucor building or one of the other real ones.  

>From the way these people operate, they should be put out of business - not just because it's a scam for the customer.  They had an error on their reactions (and building dimensions) and trying to talk to their people about it was like calling the local kindergarten...until the engineer could finally be reached after 3 days of wasting time.  

And when the contractor called about dropping the columns to the tie-rods, the woman (who wouldn't let him talk to anyone else) said, "our buildings don't need no rods or any of that stuff, they set just fine!  Our buildings are built strong!"  And this is for a 120' clear-span building.

If it wasn't so scary it would be funny.

Ed Fasula E.I.T.


> If you have the option, I would simplify the design and 
> alleviate a number
> of your concerns by extending the metal building columns by 
> 2' (or whatever
> is required) and set the column on the footing.  The portion 
> of steel column
> below grade can be encased in concrete for protection.  Just 
> another option
> to consider.
> 
> Jim Hagensen, SE  
> 
> -----Original Message-----
> From: ad026(--nospam--at)hwcn.org [mailto:ad026(--nospam--at)hwcn.org]
> Sent: Tuesday, September 26, 2000 6:46 PM
> To: seaint(--nospam--at)seaint.org
> Subject: Re: Pre-Eng. Steel Bldg Moment Ftg.w/ Tie-Rods;& 
> Base PL. Shear
> 
> 
> > From: "Ed Fasula" <tibbits2(--nospam--at)metro.lakes.com>
> 
> > We are using dropped & encased tie-rods in combination with 
> a moment =
> > footing to resist 55k horizontal.  The rods are dropped 
> about 2', so the =
> 
> > Assuming that all works, so much movement of a frame seems 
> excessive.  =
> > On the other hand, if it were a (more common) 80' building, 
> we would =
> > still have .79".  Has that been a problem?
> 
> Ask the pre-eng designer what lateral deflection is acceptable at the
> base. They are probably working to something around h/200 or more
> flexible so your base movement may not be an issue, if they can figure
> it out.
> 
> > shear.  Even without the clamping action of the anchor bolts, the =
> > horizontal thrust would nearly be accounted for by the 
> simultaneous =
> > vertical loads.  With 55 kips, it seems a little out of common =
> 
> There will be a small amount of base rotation or uneven stress
> distribution possibly coupled with a flexible plate. Clamping, at best
> will not be evenly distributed. Friction, at worst will be averageable
> up to localized shear failure of the concrete surface.
> 
> The pre-eng base plate design will probably be based on even
> distribution of shear on the anchor bolts. Adequate for small 
> stuff in a
> 2D world where anchor bolts are placed perfectly and friction/clamping
> are useful redundancies.
> 
> > I ran the numbers on a shear lug, and that method would 
> require 1" thick =
> > steel for the same force.  The text mentioned previously 
> states you =
> > can't use the lug in combination with the friction 
> procedure.  Would =
> > there be any merit to adding a 3/4" lug for added safety, 
> or might it be =
> > counter-productive?
> 
> If you're only guessing at the 75% effect then you are not 
> prepared for
> the possibility that the shear lug will actually be required to resist
> more than 75% of the shear (e.g. fails). You would need to confirm the
> relative stiffness between the shear lug and the base friction. Don't
> waste your time writing that particular PhD thesis.
> 
> Go one way or the other or both (conservative but not necessarily
> expensive) but don't try to go part way on each.
> 
> -- 
> Paul Ransom, P. Eng.
> Civil/Structural/Project/International
> Burlington, Ontario, Canada
> <mailto:ad026(--nospam--at)hwcn.org> <http://www.hwcn.org/~ad026/civil.html>
> 
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