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Re: Masonry lintel design

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Bill:

I also found an NCMA publication ("Architectural & Engineering Concrete
Masonry Detail for Building Construction") in my library of books that
shows CMU lintel shapes as having a depth of 5 1/4" from top of CMU block
to top of bottom "shell".  This would leave the bottom "shell" as 2.375"
thick.  Add 1/2" minimum for grout clearance and 5/16" for half the
diameter of a #5 and you end up with 3.1875" cover from bottom of
lintel unit to center of bar.  If you use the full nominal depth of 8",
then your d would be 4.8125".

Now, there is nothing to indicate in the publication that this is a
standard, minimum, or otherwise dimension.  But, it is somewhat consistant
with my previous suggestion of about 3" of cover.

HTH,

Scott
Adrian, MI


On Mon, 8 May 2006, Scott Maxwell wrote:

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>   seaint(--nospam--at)seaint.org at 17:11:59 on 8 May 2006.
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>
> Bill:
>
> If you are planning on using an actual lintel shape block (i.e. the "U"
> cross section shape), then I would use a cover of no less than around 3".
> Considering your typical 8" block has a face shell of 1 1/4" and a 12"
> block as a face shell of 1 1/2", it makes sense to me that the bottom
> "shell" of a lintel block will be about 1 1/2" or so.  At is at least 1/2"
> clear space for grout plus thickness of the bar, you end up with 2.5 to 3
> inches of cover to center of bar.
>
> HTH,
>
> Scott
> Adrian, MI
>
>
> On Mon, 8 May 2006, Sherman, William wrote:
>
> > I am designing a single course masonry lintel using two #5 bars near the
> > bottom of a masonry lintel block - what is a practical "d" distance to
> > use for vertical bending?  I have consulted numerous references on
> > masonry design but none of them give any guidance.  The lintel design
> > examples show an assumed "d" distance - with each reference using
> > different assumptions.  I need to get as much capacity out of the lintel
> > that I can, but I also need to make reasonably conservative assumptions
> > about the constructed condition.
> >
> > (FYI: The masonry supplier has not been selected yet, so I do not have
> > accurate information on the dimensions of the lintel block.)
> >
> > (RANT: This is the most frustrating aspect of masonry design to me - the
> > design formulas are well defined but the construction details are not
> > well defined.  It is very difficult to apply engineered design to
> > masonry, when the industry does not define such simple "details".)
> >
> >
> > William C. Sherman, PE
> > (Bill Sherman)
> > CDM, Denver, CO
> > Phone: 303-298-1311
> > Fax: 303-293-8236
> > email: shermanwc(--nospam--at)cdm.com
> >
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