Page 71 - Riem-Vol6_nº3

416 IBRACON Structures and Materials Journal • 2013 • vol. 6 • nº 3
Monitoring of crack opening in masonry and concrete using mobile platform
the masonry crack opening, which may change the quantitative
analysis. Other factor that could impose some difficult on the con-
ventional measuring is the irregular forms of the cracks on ma-
sonry. Besides that, with the quoted conventional instruments it is
not possible to detect rapidly small variations on the crack open-
ing, due to its resolution and to the used technique. As a result, it
becomes necessary to make several measures in order to obtain
a conclusive measure.
On the conventional measuring procedure there is an uncertain-
ness associated to the handling of the instrument by the techni-
cian. This way, the conventional measuring methods may gen-
erate different readings between inspection technicians, for the
same crack on masonry or concrete region. This inconsistency
demands a higher number of repetitive measures to have more
accurate values.
On the continuous crack monitoring method, the electric or me-
chanical strain gages instrument is installed between the damaged
structures [21], but demands the permanency of it between the
periodic inspections.
With the purpose of reducing the inspection technician work load
and the generation of more accurate results this proposal aims to
automate the identification of the crack opening on masonry and
inspections is conducted by the technician that uses a measuring
tool, such as a graduated scale or cracks’ comparator. Figure 1
shows one of the most used tools of the conventional method for
measuring cracks opening. The main problems about those mea-
suring by comparing methods could be enumerated as low accu-
racy and traceability, subjectivity on reading and the difficulties on
recording data [23].
Another dimensional instrument with better resolution applied on
the conventional measuring procedures is the digital pachymeter,
illustrated in the Figure 2(a).
On other conventional measuring procedure, the technician uti-
lizes blades calibrator with thickness between 0.1 mm and 2.0
mm. In this procedure the technician must choose and insert the
metallic blade in the crack opening, as shown in the Figure 2(b).
Another inconvenient on the blades calibrator procedure is the
constant insertion of metal blades. Besides the time spent on
changing the blades for the measuring, the insertion of the blades
may lead to further degradation on the crack opening area, which
could cause both mistaken measures and compromising the in-
spection process.
The conventional dimensional metrology instruments present
subjectivity on the manual positioning during the measuring of
Figure 1 – (a). Graduated scale manually put on mansory structure with crack,
on conventional measuring procedure. Figure 1(b). Crack comparator put
on a crack of a faulty structure on masonry. Figure 1(c). Scale detail of the
comparator instrument, presenting the 0.70 mm indication of a crack opening
A B C
Figure 2 – (a). Digital pachymeter on a conventional procedure of a crack on
masonry conventional measuring. Figure 2(b). Calibrator instrument formed
by blades. This instrument on a conventional measuring allows a comparative
verification between the crack openingon mansory and the blade's thickness
A B