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Since high-speed railway bridges are subjected to cyclic
loading by the continuous wheel loads traveling at high speed and regular
spacing, their dynamic behavior is of extreme importance and has significant
influence on the riding safety of the trains. To secure the
riding safety of the trains, advanced railway countries have limited the
vertical acceleration of the bridge slab below critical values at specific
frequency domains. Since these limitations of the vertical acceleration
constitute the most important factors in securing the dynamic safety of the
bridges, these countries have opted for a conservative approach. However, the
Korean specifications limit only the size of the peak acceleration without
considering the frequency domain, which impede significantly rational
evaluation of the high-speed railway bridges in Korea. In addition, the
evaluation of the acceleration without consideration of the frequency domain is
the cause of disagreement between the dynamic analysis and measurement results.
This study conducts field monitoring and dynamic analysis on high-speed railway
bridges to gather the acceleration signals and compare them. Significant
difference in the size of the vertical acceleration was observed between the
measured and dynamic analysis accelerations when discarding the frequency
domain as done in the current specifications. The comparison of the
accelerations considering only low frequencies below 30 Hz showed that the
dynamic analysis reflected accurately the measured vertical acceleration.
The design live load of
railway is divided into common railway and high-speed railway separately inKorea.
Accordingly, the Korean design specification of railway specifies the impact
factor for common railway and high-speed railway respectively. The impact
factor for high-speed railway is based on Eurocode. Since the impact factor
criteria inKoreawere established by adopting those of the Eurocode and without dedicated
investigation relying on research results reflecting the domestic
circumstances, thorough examination should be implemented on these criteria.
Therefore the evaluation of impact factor based on field tests is required.
Both dynamic and static vertical displacements are necessary to compute the
impact factor. The dynamic response can be obtained from the measurement of
deflection of the bridge slab crossed by the firstKoreahigh-speed train (KTX, Korea
Train eXpress) running at high-speed. The main difficulties encountered are in
obtaining static response because static response corresponds to the response
of the bridge when the train remains immobile on the bridge or crosses the
bridge at speed slower than5 km/hr. This study
introduces the static response derived by applying the moving average method on
the dynamic response signal. To that goal, field measurements was conducted
under train speeds of5 km/hr and ranging
from100 km/hr to300 km/hr
on Yeonjae Bridge located in the trial section of the Gyeonbu High-Speed
Railway Line before its opening. The validity of the application of the moving
average method is verified from comparison of measured static response and
derived static response by moving average method. Moreover, evaluation is
conducted on the impact factor computed for a bridge crossed by the KTX train
running at operational speed.
The research on positioning system and
spatial alignment is a big topic. In this paper, we proposed a design (that) studies
two issues. One is the study of range positioning algorithm based on ZigBee communication
system. The other one is spatial alignment platform
which is controlled with two servos. Hardware and software control system was
realized, which also consists of two parts, ZigBee network positioning system
and automatic orientation platform.