http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
정승후,이창길,김기현,여인호,이준화 한국철도학회 2023 한국철도학회논문집 Vol.26 No.9
The high-speed railway operating authority is adjusting train operating speed to prevent rail buckling based on track temperature. Expected temperature increases due to climate change will likely lead to more frequent speed restrictions in the future. However, exceeding the speed limit temperature may not always result in rail buckling, and, conversely, under conditions in which rail buckling is not expected, it may still occur due to stress concentration. If it is possible to monitor changes in axle stress based on track temperature, a scientifically grounded approach to preventing rail buckling based on stress can be developed. This study developed a detachable image-based high-precision strain measurement system to measure stress changes in continuous welded rail. The system uses three digital microscopes to measure 2-axis strains (axial and vertical) on the rail web, enabling the measurement of stress changes even in the immovable zone. Through laboratory tests with a uniaxial load, this study confirmed the possibility of measuring 1-axis strain and stress changes. The results showed that strain as small as 3με, corresponding to a temperature expansion of 0.25℃, could be measured, and the performance of the system was verified by comparing results with those obtained using strain gauges.
정승후,이준화,이경찬 한국철도학회 2023 한국철도학회논문집 Vol.26 No.4
From a long-term measurement of the 40m PSC box girder bridge of the Honam High-speed Railway, seasonal variations in structural dynamics properties of the bridge were examined. The target bridge generally showed a natural frequency of 4.5 Hz, but the natural frequency increased to at most 5.3 Hz at sub-zero temperatures in winter. The increase in natural frequency is interpreted as at most 39% increase in stiffness of the bridge in winter. It seems that the reason for the increase in stiffness of the bridge in winter is that the slab track and the bridge were fixed due to freezing and structurally integrated. When the protective concrete layer (PCL) and track slab (TCL) are integrated with the bridge structure, the flexural stiffness of the bridge increases by 30 to 40%, which is similar to the variation of stiffness according to the increase in natural frequency. However, additional experimental verification is needed in the future to determine how much the integration caused by freezing between the slab track and the bridge actually affects.
정승후,김현민,김성일,장정환,이경찬 한국철도학회 2021 한국철도학회논문집 Vol.24 No.4
The structural safety of the Honam high-speed railway system was investigated two years before its official opening in 2015. A verification test was performed to define the allowable level of maximum deflection and vertical acceleration at the mid-span of bridges on the Honam line. This study conducted new field tests to better understand the dynamic responses of the Honam high-speed railway bridges. Sensors were installed on a bottom flange of three different bridges: two prestressed concrete box girder bridges with 35m and 40m spans and one steel plate girder bridge with 50m span, to measure bridge responses when a high-speed train passes. The dynamic characteristics of the bridges, including the vibration characteristics (e.g., natural frequency and damping ratio), critical speed causing resonance, maximum responses, impact factor, and resonance level, were examined. The experimental results provide an in-depth understanding of bridge responses when resonant phenomena occur due to a running high-speed train with critical speed.