TM 5-809-3/NAVFAC DM-2.9/AFM 88-3, Chap. 3
and condition assessment in masonry structures
preferable to the mechanical pulse is when the
particularly in the case of older unreinforced brick
desired path length is very short and the quality of
masonry. The primary difference between the two
the masonry is generally good, as in through-wall
techniques is the amplitude and wavelength of the
transmission tests in grouted concrete masonry. In
input pulse, both of which are larger for the
this case, the mechanical pulse system is unable to
mechanical pulse tests. The high energy and long
detect the typically small flaws or delaminations.
f. Location of reinforcement and ties. The use
wavelength of its input wave are not as rapidly
attenuated by the boundaries between units and
of magnetic and resistance methods allows quick
mortar that are intrinsic parts of masonry
inspection of masonry construction for the presence
construction. Because of this, the mechanical pulse
of steel reinforcement or ties. These techniques
will travel farther through most masonry materials
may be useful for quality control as a means of
than the ultrasonic pulse. In addition, the
verifying compliance with construction plans, and
mechanical pulse technique is sensitive enough to
provide reasonable results when expected
detect larger flaws that are of interest in a structural
reinforcing bar sizes and locations are known.
evaluation. Thus, for masonry, the mechanical
More difficult is the case of retrofit or renovation
pulse system is generally preferable to the
projects, when it is necessary to not only locate the
ultrasonic system. Because of potential difficulties
reinforcement, but also estimate the size and depth
in the interpretation of data, mechanical pulse tests
to the bar. Commercially available equipment
are best conducted in conjunction with flatjack
typically utilizes an electromagnetic field generated
tests, so that the influence of varying vertical
around a hand-held probe to indicate the presence
stresses and varying material deformability on the
of steel in the masonry. A voltage change occurs
mechanical pulse measurements can be assessed.
when the field is interrupted by a ferrous material,
The single case where the ultrasonic pulse is
such as a steel reinforcing bar. The magnitude of
10-10
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