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RE: Steel beam unbraced length limit

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Crane vendor catalogs have a section where the
desirable combinations of channels and W-/S- sections
are listed. Use of these combination sections would
prevent the kind of problems you have mentioned.

Rajendran

--- Gary Hodgson & Associates <ghodgson(--nospam--at)vaxxine.com>
wrote:

> Matthew. 
> I try to avoid those cap channels where I can,
> because they create problems: fit up, flatness,
> sweep or camber, access for welding, stitch weld
> versus continuous, etc.  The biggest problem I run
> across is that engineers just check to see if the
> cap channel fits on the wide flange, but they never
> ensure it is wide enough for the welder to get a
> decent
> 45 degree fillet.  Just went through this with a
> customer who put a C12 on a W24.  The thickness of
> flg
> material dictated a 5/16" fillet per the welding
> code
> but in a single pass at that angle of approach gave
> him
> something like 3/16" on the vert leg.  I made him
> add a
> second pass to build up the weld to 5/16" and he was
> none too happy with me.  As if I chose the d**n
> channel.
> Gary
> happy
> 
> On 26 Feb 2005 at 9:57, Stuart, Matthew wrote:
> 
> > Probably because you placed a channel on top of
> the beam to help brace
> > the compression flange.
> > 
> > ________________________________
> > 
> > From: Gary Hodgson & Associates
> [mailto:ghodgson(--nospam--at)vaxxine.com]
> > Sent: Sat 2/26/2005 9:03 AM
> > To: seaint(--nospam--at)seaint.org
> > Subject: RE: Steel beam unbraced length limit
> > 
> > 
> > 
> > I wonder how I ever designed all those crane
> runway
> > beams of 40-50 ft length
> > Gary
> > 
> > 
> > On 25 Feb 2005 at 9:12, Sherman, William wrote:
> > 
> > > In general, I would not place a limit on
> unbraced length as long as
> > > the beam meets the code requirements. However, I
> sometimes get
> > > nervous when the allowable stress based on the
> code is very low -
> > > although this forces the applied loads to also
> be very low, it
> > > implies that the beam does not have much lateral
> stiffness.
> > >
> > > William C. Sherman, PE
> > > (Bill Sherman)
> > > CDM, Denver, CO
> > > Phone: 303-298-1311
> > > Fax: 303-293-8236
> > > email: shermanwc(--nospam--at)cdm.com
> > >
> > >
> > > > -----Original Message-----
> > > > From: Will Haynes [mailto:gtg740p(--nospam--at)hotmail.com]
> > > > Sent: Thursday, February 24, 2005 1:50 PM
> > > > To: seaint(--nospam--at)seaint.org
> > > > Subject: Steel beam unbraced length limit
> > > >
> > > > I have designed steel beams with unbraced
> lengths up to 20 ft
> > > > before (above "Lr" value).  I have had other
> engineers tell me
> > > > they won't design for an unbraced length this
> high even if it
> > > > works by AISC equations, I guess due to their
> fear of fabrication
> > > > and erection influences on the beam and this
> being magnified by a
> > > > larger unbraced length.  Isn't this already
> accounted for in the
> > > > AISC equations?  Any thoughts?
> > > >
> > > > Will Haynes
> > >
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