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Re: Designing Masonry to Span Horizontally

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> I am designing an infill wall for  PEMB.  The vertical eave height is 30
> feet.  The rigid frame spacing is 26.25 feet.  It seems to me I can span
> the wall horizontally or vertically for lateral support.  I am used to
> spanning a wall vertically but not horizontally.  How does one design the
> reinforcing?  It seems to me that it is similar to designing a vertical
> span.  The steel area I determine is used in the horizontal bond beam.
> The spacing of the steel is the spacing of the bond beam.
>
> What concerns me is that it seems to me to be is easier to build a wall
> that has vertical reinforcing than horizontal reinforcing.  I have a wide
> variety of rebar spacing options.  Also, grouting can be done in high
> lifts.  If I start requiring bond beams then the construction sequencing
> seems to slow down.  If I had bond beams at 4 feet on center then every 4
> feet they would have to stop, pour the bond beam, and start again.
>
> Am I looking at this right?  What is the best way to approach a
> horizontally spanning masonry wall?  What is the best way to attach it to
> the rigid frames?  I was thinking of a Hohmann & Barnard gripstay type
> anchor on the column.
> Rich

One important factor to consider are the vertical control joints.  If you
continue the bond beam reinforcing through the joint, it will form an ugly
crack at the joint.  If you stop the reinforcing, the bond beam is not
effective.  I had a situation where I *had* to span horizontally.  The
architect added control joints about a day before 100% CD printing, and I
had to deal with the field problems.

PEMB designers routinely design wind girts spanning between the main columns
to support the cladding.  In this situation, I'd support the CMU on the PEMB
wind girts.  You'll need to specify the horizontal load resisted by the
girts (seismic and wind from the wall), and the PEMB engineers are
responsible for designing the girts to handle it.  You'll need to find out
what girt spacings are typical, or else just specify a uniform psf and let
the PEMB designer pick the spacing that suits his typical girt size.

----
Jason Kilgore
Leigh & O'Kane, L.L.C.
816-444-3144
816-444-9655 (FAX)



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