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Re: FIRE - Fire damage to unreinforced brick wall.

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Bruce Resnick wrote:

>URM is inherently unsafe in seismic country.<

You could have stopped after the 4th word!

Being in seismic zone 2, I have been very concerned about the UBC
and ACI 530 wall reinforcing requirements for masonry walls that
have appeared in the UBC since 1985.  These reinforcing
requirements (94 UBC 2106.1.12.3) are based on limited tests
performed for HUD for *very* small, lightly loaded single story
residential structures.  Somehow, *someone* extrapolated the
results from this very restrictive test to *any* masonry
structure and convinced ICBO and ACI to incorporate them in their
codes.

Regardless of what the codes will permit, I still use the
.002A(g) minimum when I design masonry walls.  Masonry is a
brittle material, and we need the reinforcing to make it behave
like a ductile material.

Getting back to the original subject, if one wythe has to be
replaced, I think that I would consider using WWF or expanded
metal in the collar joint and bolting or otherwise connecting the
two wythes together so as to provide some ductility to the wall.

A. Roger Turk P.E.(Structural)
Tucson, Arizona

P.S.  Not only do we have to confront the masonry reinforcing
provisions of the UBC here in Tucson, but local amendments now
permit *straw bale* and rammed earth construction in spite of
opposition from the Tucson Chapter, SEAOA.  Local builders also
want to use mud adobe and burnt adobe, which is mud adobe fired
at unknown temperatures for an unknown length of time in kilns of
various construction just across the border in Mexico.