TM 5-809-3/NAVFAC DM-2.9/AFM 88-3, Chap. 3
test is then conducted on the same joint for several
determined by arbitrary methods, such as a certain
levels of normal stress, so the friction angle is
number of tests per square foot, etc. It remains only
measured directly rather than assumed. Electronic
to conduct the simpler single flatjack test to
deformation measuring devices are used to monitor
determine the variation of normal stresses
the movement of the unit continuously during the
throughout the structure.
d. Ultrasonic Pulse. The ultrasonic pulse
test, thus eliminating ambiguity concerning the
definition of failure. The influence of the collar joint
velocity (UV) technique uses electroacoustic
may be estimated based on a collar joint shear test.
transducers to pass a high frequency (50,000 Hz)
Only the effect of workmanship remains a potential
stress wave through masonry. This technique has
source of error. The test setup for the modified in-
good potential for evaluation of masonry structures
place shear test is shown in figure 10-4. Results
and is most useful for the location of relatively
from this test show the relationship between
small flaws in otherwise uniform masonry materials.
increasing normal load and the resulting increasing
In certain cases, it may be possible to obtain an
deflection.
estimate of masonry compressive strength from
(3) Application. Because the in-place shear
ultrasonic pulse velocity measurements. However,
test measures the bed joint shear strength directly
very careful interpretation of the signal is required
with a minimum of damage to the structure, it is an
along with a meticulous visual survey in order to
essential part of any building evaluation where
interpret the data properly. It is recommended that
lateral loads influence the building design. In some
pulse velocity techniques be used in conjunction
seismic regions, the existing test is required for
with other NDE tests such as the flatjack test for
some retrofit designs. The modified test should be
determining the state of stress and deformability in
conducted as an extension of a normal series of
walls and also with destructive tests to verify the
flatjack tests. The single-flatjack test reveals the in-
deformability and strength.
(1) Background. The ultrasonic pulse
situ state of normal stress at the test joint, and thus
provides essential data for determining the
velocity technique has only recently been applied to
expected joint shear strength in the area of the test.
masonry. The studies to date have been mostly
The two-flatjack test provides half of the required
exploratory, evaluating the feasibility of using the
test setup for the modified in-place shear test. At
method on masonry structures. The technique has
the completion of the test, the engineer should
been used effectively for concrete using ASTM C
know the relationship between the expected joint
597 for quite some time, hence the literature on
shear strength and the normal stress along with the
testing concrete using ultrasonic pulse velocity
measured normal stress at the test location. If
techniques is extensive. The method has proven to
similarity of materials throughout the structure can
be reasonably accurate for predicting concrete
be established using a technique such as the
compressive strength using empirical relationships
Schmidt Hammer test, the number of required in-
that were derived under carefully controlled labo-
place shear tests can be reduced from the number
ratory conditions. However, a multitude of factors
10-6
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