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› Mae 59
› LOAD TESTS
The load tests have the primary objective
to compare the experimental
arrows obtained during the testing
phase and the theoretical arrows
of the project, in order to evaluate
the deformation profile of the element
tested. The test loads used can
be distributed (bricks, blocks or cement
bags, water tanks) or similar
concentrates (hydraulic jacks). The
tests that use similar concentrated
loads can be of pull or push test type.
The result of the load tests and elastic
behaviour of the structure is represented
through load/shift graphs and
hysteresis curves. The measurement
of the shifts and deformations can be
taken with manual systems, such as
mechanical comparators or deflectometers
or with automatic-electric
systems, such as movement transducers
(resistive, inductive, potenziometric).
The use of these electric systems
allows continuous, stable and
precise readings that can be transmitted
also far away from the relative
testing area. Rapidity of execution, accuracy
and safety make this system
the most diffused one nowadays, in
the test and trial sector.
› MEASUREMENT OF THE HEAT TRANSMISSION IN GROUNDS
The measurement method is based
on the so called unstable sensor technique,
that uses a probe (also called
thermal needle), which mounts a heating
wire and a temperature sensor. The
probe is introduced in the ground. From
its response when subject to a heating
cycle for a few minutes, it is possible
to calculate the thermal resistivity (or
its opposite, the heat transmission).
The principle of the measurement is
based on a peculiar characteristic of
a rectilinear heat course (the heating
wire of the probe): after a short transitional
period, the increase of the temperature
depends only on the heating
power and heat transmission of the
medium. Once the first is known, the
second can be calculated. The main
applications of the technique consists
in the testing of high voltage cables
and heating ducts.