Need a book? Engineering books recommendations...

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

Re: GL beam strengthening

[Subject Prev][Subject Next][Thread Prev][Thread Next]
If the concentrated loads need to be transferred at
each end then how do flitch beams work? The ones I've
seen have a steel plate that does not bear on the end
supports and have uniform bolting 1 to 2 ft O/C.
Irv


--- "Gerard Madden, SE" <gmse4603(--nospam--at)gmail.com> wrote:

> model you original beam as taking 40% of the uniform
> load (or whatever the
> new beam isn't carrying) with a concentrated load at
> each end where you are
> terminating the second beam and check the original
> for shear, bearing etc...
> doesn't seem too hard... ofcourse, make sure your
> connection at the end of
> the sistered beam can transfer the load.
> 
> hth,
> -gm
> 
> On 6/2/06, Scott Maxwell <smaxwell(--nospam--at)engin.umich.edu>
> wrote:
> >
> > The different widths would explain the difference.
> >
> > My only concern with the idea is that since the
> new beam is only on one
> > side, you might need to worry some about some
> eccentric loading when
> > transfering the shear from the new beam into the
> "old" beam to take to the
> > supports.  I don't know if I really consider this
> a "deal breaker" but at
> > minimum I would likely not design the transfer
> mechanism to just the
> > minimum shear load transfer.  You might be better
> off sandwiching the old
> > beam with two new beams.
> >
> > Scott
> > Adrian, MI
> >
> >
> > On Fri, 2 Jun 2006, Joseph  Grill wrote:
> >
> > > The load sharing is all designed per deflection
> compatibility.  I don't
> > have
> > > the calcs in front of me here at home, but I
> think the difference is
> > that
> > > the new beam is a 5 1/8" thick member not 6 3/4"
> and that 60% figure I
> > gave
> > > is only "close" as my concern is at the support
> if the 12" beam is the
> > only
> > > one being supported.  Note, that I am not done
> yet (I am working through
> > > some iterations of different sizes for the new
> beam) and I also have to
> > go
> > > back through to check for errors (I don't have
> anyone in the office to
> > do
> > > that for me) so the figures I've given are not
> "on the nuts".  The
> > bolting
> > > is designed to transfer that load across the
> joint (the correct
> > percentage
> > > of loads were used for the bolting).  As of yet
> there is no dead load on
> > the
> > > beam as the joists have not yet been installed
> so no shoring or jacking
> > will
> > > be required at this time.
> > >
> > > My main concern is more of a general question in
> nature.  I'm asking (or
> > > trying to but not well) if I can bolt the new
> beam to "back to the
> > existing"
> > > near the support with adequate bolting (or
> whatever) to transfer that
> > 60% or
> > > 75%, or whatever it may be in the end that the
> new beam is carrying,
> > with
> > > the 12" beam being the only beam supported.  I
> haven't worked out the
> > > connection yet, but I don't want to detail
> additional support for the
> > new
> > > beam if the existing beam is adequate in shear. 
> Lets say the portion of
> > the
> > > total load that the new beam carries is 8000
> pounds.  I would have to
> > > transfer 4000 pounds back to the existing beam,
> at or very near the
> > support,
> > > if the existing beam is the only one supported
> (in this case a masonry
> > > wall).  That 4000 pound transfer would be made
> with 4 or 5 bolts,
> > whatever
> > > required, in a tight pattern near the support
> for the 12" beam.  The 12"
> > > beam then transfers the entire reaction for the
> composite section to the
> > > support.  Hope this all makes sense.  I'll try
> to explain again later,
> > if
> > > not.
> > >
> > > But for now it is Friday evening and I am headed
> for the martini shaker.
> > >
> > > thanks for the replies,
> > >
> > > Joe
> > >
> > >
> > > ----- Original Message -----
> > > From: "Scott Maxwell" <smaxwell(--nospam--at)engin.umich.edu>
> > > To: "'seaint'" <seaint(--nospam--at)seaint.org>
> > > Sent: Friday, June 02, 2006 6:00 PM
> > > Subject: Re: GL beam strengthening
> > >
> > >
> > > Joe:
> > >
> > > As someone else hinted at, you need to make sure
> that your load sharing
> > > percentages are determined by
> deformation/deflection compatibility.  It
> > is
> > > not clear from your post if the 60% to the new
> beam was determined from
> > > relative strength or deflection compatibility,
> but by doing a quick
> > > deflection capatibility calc I get that the new
> beam would take roughly
> > > 75% of the load.  My calc assumed that both
> beams were of the same
> > glulam
> > > grade (i.e. in theory the modulus of elasticity,
> E, would be the same).
> > >
> > > Regards,
> > >
> > > Scott
> > > Adrian, MI
> > >
> > >
> > > On Fri, 2 Jun 2006, Joe Grill wrote:
> > >
> > > > A client has installed a glue-lam beam of the
> incorrect size (too
> > small).
> > > > The beam installed is a 6 ¾" x 12" GL.  It is
> early enough in the
> > project
> > > > to
> > > > do a fix, but they don't want to remove and
> replace.  I have sized an
> > > > additional GL to be installed next to and
> bolted to the existing
> > bm.  The
> > > > new beam is 16 ½" deep.  The original beam is
> bearing on top of a
> > masonry
> > > > wall, therefore the new beam can't bear on top
> of the wall due to the
> > > > deeper
> > > > section.  The original beam can take all the
> shear by itself, but just
> > > > barely.  The new beam takes about 60% of the
> load. Bolting along the
> > beam
> > > > is
> > > > designed to transfer that 60% across the
> joint.  If I cut the new beam
> > off
> > > > at the face of the wall can I provide bolting
> at the end of the new
> > beam
> > > > to
> > > > transfer its 60% back into the 12" deep beam? 
> Or, am I missing
> > something?
> > > >
> > > >
> > > >
> > > > This would be the easiest installation, then I
> don't have to design
> > any
> > > > hangers at the wall.
> > > >
> > > >
> > > >
> > > > Thanks,
> > > >
> > > > Joe
> > > >
> > > >
> 
=== message truncated ===


__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around 
http://mail.yahoo.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 
******* ****** ****** ****** ******* ****** ****** ********