Avila Borrero Veronica Jazmin
A study on structural behavior of a compact cross section bridge
Academic advisor: Miyashita Takeshi
In recent years innovation in bridges construction has significantly progressed.
Japan engineering gave a step forward by constructing the first compact cross
section bridge, Kanayago viaduct. Since it is the first bridge of its kind constructed
in the country, the study of its structural behavior is important in order to know
if it is viable to keep implementing this construction method.
Loading tests, as well as, finite element model are the most common tools used to do
studies on a structure after its construction. The subject of the present thesis includes
the realization of a finite element model in order to study the behavior of the viaduct.
Several loading tests were carried out to collect information about the viaduct. The model
was validated by comparing the deflections obtained in the analysis with the deflections
obtained in field loading tests. Although three different types of field tests were
performed, only the static loading test was used to validate it.
The dynamic loading test was carried out in order to obtain the frequencies at which
oscillates the viaduct, through the placement of accelerometers at strategic points
along its longitudinal axis. Kanayago viaduct was monitored for an extended period of
time, where in addition to recording the frequency at which ranged the viaduct; data
such as temperature and humidity were also monitored.
Normally, when the ambient temperature increases, the natural frequency of an object,
or in this case a bridge, tends to diminish or decrease. However, according to
measurements taken in the field, Kanayago Viaduct presents a completely opposite behavior,
since when having increases in temperature; increases in the value of the frequency of
the viaduct were recorded.
The behavior presented in the model is contrary at what is actually happening in Kanayago
viaduct. This can be explained because the strength and stiffness properties of steel
and concrete degrade when temperature increases. If it is considered also thermal expansion
coefficient, changes in geometrical dimensions are added to the recreation of the model.
Despite the behavior of the model indicates an increasing natural frequency with an increase
in temperature, the variation is too small to be considered as an increment in the frequency.
This suggests that not only the temperature may be affecting the structure, but also factors
such as tensile stresses or axial forces. However, this has to be verified with further analyses.
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