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Re: Survey: Joint/Ladder Reinf in Masonry

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Syed,

It is not that "no" joint rebars are used in California, horizontal
reinforcement is used.  The issue is the type of horizontal reinforcement.
Wire reinforcement (joint ladder style reinforcement) is rarely used in
California.  Standard masonry construction is fully grouted with #4 or #5
reinforcement in both directions.  The reasons for this are varied, but is
typically a response to the high seismic demand.  The argument that
partially grouted walls reduce the seismic mass and therefore the demand is
valid to a point, but realistically only for smaller structures.  Full
grouting is required for the net shear area of the wall in most
applications, and high strength block (2000 to 3000 psi) is common.  The
basic minimum steel areas for zone 4 masonry make the use of wire
reinforcement less attractive.  Wire reinforcement either ends up on every
course or of wire diameter that I personally think is too large for proper
use in just a bedded joint.

On larger projects, it is not uncommon to exceed the permissible masonry
shear strengths requiring horizontal shear steel terminated in standard
hooks.  On one recent project the horizontal steel requirement for shear was
literally twice the vertical steel requirement for out of plane bending.
Without solid grouting the walls would not have calc'ed out at all,
requiring a switch to formed concrete walls.

On another note, I have had at least two owners in my career who were dead
set against the use of joint style reinforcement because of corrosion and
staining issues on previous projects in other areas.  I do not know if this
is a common problem, we typically do not use joint reinforcement anyway.

Paul Feather


----- Original Message -----
From: "syed faiz ahmad" <syedfaiz23(--nospam--at)hotmail.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Tuesday, December 11, 2001 5:34 PM
Subject: RE: Survey: Joint/Ladder Reinf in Masonry


> Mike,
>
> You must confirm if  really no joint rebars are used in California.
Because,
> joint rebars are required to give stifness to the CMU, besides taking care
> of cracks.
>
> For seismic detailing both the joint rebars & the vertical rebars (in the
> grouted cells) are very essential & are common place. Why is it then not
> used in California? It doesn't make sense to me.
>
> Regards,
>
> SYED FAIZ AHMAD; MENGG, MASCE
> SENIOR STRUCTURAL ENGINEER
> SAUDI OGER LTD,
> RIYADH, SAUDI ARABIA.
>
>
> >From: "Sherman, William" <ShermanWC(--nospam--at)cdm.com>
> >Reply-To: <seaint(--nospam--at)seaint.org>
> >To: "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
> >Subject: RE: Survey: Joint/Ladder Reinf in Masonry
> >Date: Mon, 10 Dec 2001 14:14:14 -0500
> >
> >Where minimum wall reinforcement is required in codes, they typically
> >require either prefabricated joint reinforcement at 16-inch vertical
> >spacing
> >or rebar at maximum 48-inch vertical spacing. For partially grouted
walls,
> >I
> >typically use prefabricated joint reinforcement to avoid numerous bond
> >beams
> >in the wall. For fully grouted masonry, I typically use rebar at 4-ft max
> >since it has to be fully grouted anyway. But I have sometimes used bond
> >beams at 4-ft on center in partially grouted walls where they can also be
> >used as lintel beams over windows and doors.
> >
> > > -----Original Message-----
> > > From: Michael Bryson [mailto:MBryson(--nospam--at)mhpse.com]
> > > Sent: Monday, December 10, 2001 10:44 AM
> > > To: 'seaint(--nospam--at)seaint.org'
> > > Subject: Survey: Joint/Ladder Reinf in Masonry
> > >
> > >
> > >
> > > I wonder how many people call out joint reinf in their CMU
> > > walls instead of
> > > rebar? It seems nobody uses joint reinf in California while it is more
> > > common back East. Is there a specific reason why?
> > >
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>
>
> SYED FAIZ AHMAD; MENGG, MASCE
> SENIOR STRUCTURAL ENGINEER
> SAUDI OGER LTD
> RIYADH, SAUDI ARABIA.
>
>
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