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The
building was a reinforced concrete school building three stories
high of U-shape, which was constructed in 1997 and then donated
to the school by a real estate company for using in teaching
of elementary and secondary levels. The construction was carried
out in a hurry during the time that economic recession was about
to begin. When looked from outside, structure of the building
was in a good condition. But when the school had an idea of
adding the fourth story on top of the existing building, which
was now deck of the building, drawings of the building were
checked in detail. It was found that more than seventy beams
which were 7 meters long could not support the new load. Thus,
these beams were designed for strengthening with carbon fiber
composites to make them be able to carry the new load safely.
After the surface of these members was removed in the process
of surface preparation, cavities inside the beams along with
many cracks were revealed. When strength of the concrete was
tested by means of Ultrasonic Pulse Velocity Method and by coring
out concrete samples for laboratory testing, it was discovered
that many parts of the concrete had low compressive strength
and could be considered as unsafe. Before strengthening of the
structure with carbon fiber composites but after the defective
parts of the structure were repaired, load test was carried
out. Results obtained from load test indicated that structural
behaviors under the applied loads could be taken as acceptable.
Thus, the structure was strengthened in the next step with carbon
fiber composites as it was designed for earlier, with some modification
made by considering results from load test. After the structure
was strengthened, load test was carried out again. Results from
load test carried out after strengthening indicated that the
structure was able to carry the new load. |
