• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.821-828
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• 2011

A significantly larger lateral load and moment are applied on a high speed railway bridge foundation than other bridge foundations. Therefore most of bridge foundations on Honam high speed railway project were designed by high strength steel pipe piles to resist lateral load and moment, which caused the increase of construction costs. In order to perform optimum design, it is important to estimate accurate lateral resistance when designing this type of structure. Lateral load tests were carried out based on the field design data with the purpose of examining the lateral behavioral characteristics of a railway bridge foundation. The standard load test method(ASTM D 3966) was used for field tests by applying twice of design load. Total four load tests were performed on high speed railway bridge foundations with strain gages installed by every 1m along piles to measure load-resistance characteristics under applied lateral loads. The back-calculated P-y curves from strain gages were compared with estimated P-y curves using theoretical methods based on geotechnical investment data. Back-calculated P-y curves from field tests for sand and clay ground conditions were presented in this paper, which are different from theoretical P-y curves. By using the research results of this study, more accurate estimations of pile design under lateral loads can be available for similar geotechnical conditions.

• 한국재료학회지
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• 제28권12호
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• pp.702-708
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• 2018

This study deals with the effect of microstructure factors on the strain aging properties of API X70 pipeline steels with different microstructure fractions and grain sizes. The grain size and microstructure fraction of the API pipeline steels are analyzed by optical and scanning electron microscopy and electron backscatter diffraction analysis. Tensile tests before and after 1 % pre-strain and thermal aging treatment are conducted to simulate pipe forming and coating processes. All the steels are composed mostly of polygonal ferrite, acicular ferrite, granular bainite, and bainitic ferrite. After 1 % pre-strain and thermal aging treatment, the tensile test results reveal that yield strength, tensile strength and yield ratio increase, while uniform elongation decreases with an increasing thermal aging temperature. The increment of yield and tensile strengths are affected by the fraction of bainitic ferrite with high dislocation density because the mobility of dislocations is inhibited by interaction between interstitial atoms and dislocations in bainitic ferrite. On the other hand, the variation of yield ratio and uniform elongation is the smallest in the steel with the largest grain size because of the decrease in the grain boundary area for dislocation pile-ups and the presence of many dislocations inside large grains after 1 % pre-strain.