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Re: Erecting Steel Braced Frames with Bolted Connections

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To the steel detailing mailing list...

I'll bet some of you detailers and/or fabricators have some experience in
this area.  I'll appreciate your feedback and (assuming the engineers are
interested), will forward it back to the engineers' list.

Thanx,

Fountain E. Conner, P.E.
Gulf Breeze, Fl. 32561
   Phone 850-932-5547
   Fax      850-934-1916

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> From: Garry Frederick <GFREDERICK(--nospam--at)HNTB.com>
> To: 'seaint(--nospam--at)seaint.org'
> Subject: Erecting Steel Braced Frames with Bolted Connections
> Date: Thursday, June 24, 1999 4:40 PM
> 
> 
> > What facilitates erecting steel braced frames with bearing bolted
> > connections when using standard holes whose diameters are 1/16-inch
> > greater than their matching bolts? Recently a 22-foot by 22-foot by
> > 100-foot high tower whose X-braces crossed at the mid-span of beams at
> > alternating floors went up poorly because the holes in the braces did
not
> > match the holes in the connecting plates on the columns and beams. Even
> > after reaming some of the mismatched holes to accommodate the next
larger
> > diameter of bolts, more than 120 mismatched holes remained. What
finally
> > enabled the tower to be erected within tolerances per section 7.11
Frame
> > Tolerances of the 1986 AISC Code of Standard Practice was by welding
> > instead of bolting the braces to the beams.
> > 
> > What may have caused the bolt holes to be so mismatched? The base
plates
> > for the columns had been positioned within the erection tolerance of
plus
> > or minus 1/8-inch of the design elevation per section 7.6 Bearing
Devices
> > of the AISC Code of Standard Practice. The wide-flanged beams, columns
and
> > braces had been milled and fabricated within the tolerances per ASTM
A6.
> > 
> > Does the accumulation of mill, fabrication and erection tolerances
> > preclude using bolted braces with standard round holes unless extra
> > measures are taken beyond standard construction? Do base plates need to
be
> > exactly at the design elevation with no plus or minus 1/8-inch
tolerance?
> > Do bolted braced frames need to be assembled in the shop by the
fabricator
> > to insure ease of erection by the erector? Does the contractor always
need
> > the option of welding the braces?
>