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RE: Mass realty check...

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David,

I agree with what Jason has just posted.  My two
cents, here in CA, especially the SF bay area, there
are plenty of URM bldgs that have been upgraded from
some old mill, industrial warehouse, etc to live/work
lofts that sell for about $500/sf.  (Ridiculous...)  

I've worked on a few of these projects.  For the most
part, the retrofit program was based on the UCBC
(Uniform Code for Building Conservation), part of the
soon to be outdated UBC (dysfunctional) family of
codes.  Based on the level of retrofit, the retrofit
could be really basic (tying diaphragms to URM walls
for out-of-plane protection) to a "full" retrofit of
using shotcrete to the URM walls, and basically
neglecting the in-plane shear resistance of the URM
(except for its mass contribution...)

If I remember correctly, a change of use dictates
upgrade to "full" code compliance.  However, I believe
that such a retrofit would be only to 75% of code,
since you are working with a structure of "archaic
materials."  

What we've done on such URM retrofits, we'll have the
mortar tested for shear.  Usually, it was about 5
tests per level at various locations (interior and
exterior).  From this, an allowable shear value for
in-plane forces is given (and hopefully agreed upon by
the governing building dept).  The wall piers that
meet the aspect ratio may be analyzed for in-plane
shear.  If they don't work, then you look at shotcrete
or steel bracing as you've mentioned.

The other items tested are epoxy anchors.  They are
tested at various locations in the varying multi-wythe
walls for tension (direct) and shear values (torque
testing).

It's not impossible for the owner to upgrade the
structure.  But, if they want to get top  dollar for
their investment, having a properly retrofitted
structure that "meets" current code is a nice selling
point.  Also, we're talking about MA, which shouldn't
see eqk's as strong or frequent as us Left Coasters...

Sorry for the long rant...

David Topete, PE
SF, CA



		
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