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RE: No special inspection of CMU walls

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I admit that I have no personal experience with a Pachometer. When I needed
confirmation of steel in either a URM wall or in a retaining wall, I hired a
laboratory who tested the walls and reported the size of steel (horizontal
and vertical), the depth of the steel relative to the face of the wall and
the spacing of the steel. I assume their reports to be accurate unless they
issued disclaimers to that affect.

To be specific - Specialized Testing (I believe they were in Glendale at the
time) tested the infills on a URM wall in Santa Ana for the size and spacing
of rebar dowels in a number of window infills.

Either MEC Labs or Specialized Testing performed a Pachometer test on a
500-foot long retaining wall in the Valencia California area to identify the
size (vertical and horizontal), spacing and depth of steel in a failing
retaining wall. In this case, I used Retain-Pro combined with the original
engineer's drawings to verify adequacy of the original design and did not
inform the testing agency of my results. I was able to ascertain that the
only way the stem could fail if the boundary conditions (soil pressure,
slope pressure, etc) were correct was by misplacement of the vertical steel
from the back of the wall to the center of the wall. In this case, the
Pachometer reported the steel to be close to the face of the wall at the toe
side which was not where the design drawings indicated the steel to be. A
core was taken to confirm the results - which it had.

Smith Emory Labs in Los Angeles performed Pachometer tests as well on
various masonry projects that were of concerned after the Northridge
earthquake.

Beyond that, I only used the interpretation provided by the testing agency
to complete my design and did not have specific knowledge of the equipment
manufacturer or model number. You might try contacting the test labs I noted
above to ask for their guidance.

Regards,
Dennis S. Wish, PE


-----Original Message-----
From: Omar M. Waqfi [mailto:OMW(--nospam--at)eqe.com]
Sent: Friday, February 02, 2001 9:34 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: No special inspection of CMU walls




I have used Pachometers to investigate reinforcement in masonry walls. I
know of
no particular brand than can locate accurately the reinforcement identifying
the
size, spacing and edge distacne. Which type are you referring to.








"Structuralist" <dennis.wish(--nospam--at)gte.net> on 02/02/2001 05:08:11 PM

Please respond to seaint(--nospam--at)seaint.org








 To:      seaint(--nospam--at)seaint.org

 cc:      (bcc: Omar M. Waqfi/EQE)



 Subject: RE: No special inspection of CMU walls








A Pachometer test should also identify the size, spacing the distance from
the face of the wall to each bar. a couple of cores (or whatever the code
might recommend for sampling) should confirm the quality of the grout and
some hammering might help locate voids if the grout was not properly placed
in lifts and there is any suspicion of voids.

Dennis

-----Original Message-----
From: Paul Crocker [mailto:paulc(--nospam--at)ckcps.com]
Sent: Friday, February 02, 2001 2:04 PM
To: 'seaint(--nospam--at)seaint.org'
Subject: RE: No special inspection of CMU walls


"If the quality is there, the samples should test ok and I'd think you might
be willing to assume responsibility.... but I think that's an important
element... what additional responsibility you are willing to assume to make
up for the contractor's oversight."

There is a big difference between flexiblity in what evidence you require
that your design intent has been met and assuming responsibility for the
final product.  I can't imagine many occassions where you would want to do
the latter.  The former is generally acceptable if you can come up with
something that all concerned parties (the owner, city, etc.) are happy with.
Quite a while back I worked on a job where they did a portion of the work
without inspection.  The inspector had seen the work at about 70% complete,
and the contractor had a great deal of confidence in it (a contractor with
good creadibility, mind you), but the final detailed inspection was missed.
I think they also did various tests to establish what was in place.  They
asked if we could accept the evidence.  Yes.  They asked if we would sign
something accepting responsibility for what had been done and verifying that
the work was acceptable.  No.  How could we?  We didn't do the work or the
tests.  In much the way that you might accept a concrete cyclinder test from
a testing agency, you are accepting the results but not accepting
responsibility for the process itself.

A friend of mine got paid to do a summer of non-destructive and slightly
destructive testing in a situation not too different from yours, by the
sound of it.  It involved lots of cores, drilling and chipping to verify
grouting and reinforcement.  This is one way of dealing with it.

Paul Crocker