Return to index: [Subject] [Thread] [Date] [Author]

RE: x-bracing connections

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Ron,

You won't really get that much prestress.  First the bolts are in only one
leg, and the angle will bow a bit.  Secondly there is 1/16" over size in the
holes at each end.  Third, the holes in the gusset and in the angle will
deform locally.  Fourth, the anchor bolt holes are a minimum of 5/16" over
the nominal bolt size.  But there will be some stretch in the brace.

When I was an iron worker it was common practice to drive the bull pins to
make the connection.  When I was a steel detailer, it was common practice in
our shop to detail the braces 1/8" short, and provide 2 bolts as a minimum
on each end.  Now as an engineer, I rely on the detailers and the iron
workers to get it right.  But I still show 2 bolts as a minimum on each end
of the brace.

Regards,
Harold O. Sprague

> -----Original Message-----
> From:	Ron Hill [SMTP:ronhill(--nospam--at)hillce.com]
> Sent:	Wednesday, February 06, 2002 2:29 PM
> To:	seaint(--nospam--at)seaint.org
> Subject:	RE: x-bracing connections
>
> Harold,
>
> Thanks for the information.  I was thinking about the solution and adding
> slack to the brace rather than making it shorter.  It seems easier to bow
> the angle than stretch it.  A quick check of a 16 foot length shows 30
> kips
> is required to stretch 1/8".  That is a lot of prestress.
>
> Ronald Hill, P.E.
> HILL Consulting Engineering
> PO BOX 26525
> Birmingham, Alabama 35260 USA
> Phone: 205.823.4784
> FAX: 205.823.4145
> Email: ronhill(--nospam--at)hillce.com
> Efax: 509.275.8095
> http:\\www.hillce.com
>
> -----Original Message-----
> From: Sprague, Harold O. [mailto:SpragueHO(--nospam--at)bv.com]
> Sent: Tuesday, February 05, 2002 11:55 AM
> To: 'seaint(--nospam--at)seaint.org'
> Subject: RE: x-bracing connections
>
>
> Ron,
>
> X-bracing can be a problem, but is easily fixed.  Many savvy detailers
> will
> detail X-braces 1/8" short, and use 2 bolts at each end as a minimum.
> Then
> the iron workers will drive bull pins (or drift pins depending on the iron
> worker regional jargon) in the outboard holes to line up the second hole
> and
> install the bolt.  The bull pin is then removed and the other bolt is
> installed.
>
> Another approach is to use over sized holes in the gusset and use a slip
> critical connection.  This is a good solution when you have a lot of bolts
> and claw angles where fit up can be problematic, but is over kill for only
> a
> little L 3x3x1/4 X-brace.
>
> Tell the iron workers that if they knew ANYTHING about hanging iron there
> should be no problem.  Oh yeah, then you need to run like hell!!
>
> Regards,
> Harold O. Sprague
>
> > -----Original Message-----
> > From:	Ron Hill [SMTP:ronhill(--nospam--at)hillce.com]
> > Sent:	Tuesday, February 05, 2002 11:32 AM
> > To:	Seaint@Seaint. Org
> > Subject:	x-bracing connections
> >
> > I have a client that says he has problems in the field with bolting
> > x-bracing.  The diagonals are generally 3x3 x1/4 angles bolted to
> gussets.
> > The holes are 13/16" diameter predrilled for 3/4" bolts.  They claim
> that
> > the holes never align.  They want to maintain an all bolted erected
> > structure and welding the angle to the gusset is not an option.
> >
> > Has anyone had this problem with miss matched holes??  They claim the
> hole
> > locations are correct based on shop drawings but they think tolerances
> > cause
> > the problem.
> >
> >
> >
> > Ronald Hill, P.E.
> > HILL Consulting Engineering
> > PO BOX 26525
> > Birmingham, Alabama 35260 USA
> > Phone: 205.823.4784
> > FAX: 205.823.4145
> > Email: ronhill(--nospam--at)hillce.com
> > Efax: 509.275.8095
> > http:\\www.hillce.com
> >

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
*
*   This email was sent to you via Structural Engineers
*   Association of Southern California (SEAOSC) server. To
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you
*   send to the list is public domain and may be re-posted
*   without your permission. Make sure you visit our web
*   site at: http://www.seaint.org
******* ****** ****** ****** ******* ****** ****** ********