• Tunnel and Underground Space
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• v.10 no.2
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• pp.196-210
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• 2000

This study was aimed to verify the validity of the flexural toughness evaluation method of steel fiber reinforced shotcrete(SFRS) currently being adopted by Korea Highway Corporation(KHC). Total 33 beam specimens using six different kinds of steel fiber products were prepared at tunnel construction sites and flexural toughness tests were executed at laboratory. Equivalent flexural strengths and toughness quotients were evaluated from the tests following the KHC guide iud these were compared with the quality grades determined under the guides proposed by ASTM, ITA and EFNARC. To discard the disadvantage that the toughness quotient could be influenced by flexural strength when following the KHC guide, a modification substituting the designed flexural strength for the flexural strength in the toughness quotient calculation formula was proposed to rate the quality of SFRS more adequately.

• Journal of the Korean Society for Railway
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• v.13 no.2
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• pp.201-207
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• 2010

The replacement criterion of rail by accumulated passing tonnage was estimated by the bending fatigue life of rail. In order to estimate the bending fatigue life, it is basically needed to analyze bending fatigue behavior on the rail. In this study, the bending fatigue test were performed for 50kg/m and 60kg/m rails, and test specimens were distinguished by new and used rails and by the types of welded rail such as base material, thermite weld, and gas pressure weld. Also, this study analyzed the fractured surface, the position of initial crack and the bending fatigue behavior (S-N curve). Therefore, it evaluated S-N curve for welded rails according to the fracture probability. The result from this study might be used essential data in order to estimate the bending fatigue life of rail by the accumulated passing tonnage.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1A
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• pp.35-43
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• 2006

In this paper, procedures and research results involved in the development of glass reinforced composite bridge deck of hollow section were presented. Laminate design for the 3 cell deck section was performed. Structural characteristics such as serviceability, strength, failure and stability for DB24 load were analytically studied through the finite element analysis for the composite deck plate girder bridge. Composite deck tube was fabricated with pultrusion and extensive tests such as flexural test, girder-connection test, barrier-connection test, compression fatigue test and flexural fatigue test were carried out to evaluate structural behavior experimentally. Also, field load test was conducted for the demonstration plate girder bridge with composite deck and requirements for the strength and serviceability were reviewed.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.4 s.74
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• pp.337-345
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• 2006

In this study, to evaluate fatigue characteristics of developed composite bridge deck, compression fatigue test at girder support and flexural fatigue test for the 2.8m-long flexural test model were carried out. For the test specimen, DB 24 truck load was applied up to 2,000,000 cycles. In the compression fatigue test, behavior at deck tube and its bonded connection were evaluated. In the flexural fatigue test, deck behavior at mid-span and girder connection were evaluated.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.2
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• pp.299-306
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• 2015

The quality for the domestic pavement is evaluated based on flexural strength at the age of 28 days in accordance with KS regulation. Most specimens of the flexural tensile strength used currently are relatively large ones with a dimension of $150{\times}150{\times}550mm$. Accordingly, it is difficult to treat the specimens, and the utilization of a curing tank is low. In this paper, the study tried to resolve the problem by specimen size specified in the code. For this purpose, a flexural strength test was conducted according to the log scale within the specimen size specified by the KS. And, based on the results of this experiment, a comparative analysis was conducted using the prediction formula of Size Effect Law (SEL) proposed by Bazant to examine the correlation between specimen sizes, so as to use the result as basic data for the reduction of the specimen size in the quality evaluation of concrete pavement.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.5
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• pp.3251-3259
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• 2014

This paper presents experimental and analytical research results to predict nonlinear flexural behavior of corroded reinforced concrete beams. For this purpose, a series of test and an analytical simulation using the Maaddawy's model were carried. Test specimens of total 12 RC beams were placed in accelerated corrosion status using salt water spray test chamber for 5 months and 10 months, after they were preloaded up to 30% and 60% of the maximum load corresponding to nominal flexural strength. The test results showed that flexural strength and ductility decreased to 5.4% and 43% at the most respectively due to breakdown of bond at the steel-concrete interface. Comparative study between the analytical predictions and the experimental results showed that the Maaddawy's model can be applied to predict a real corroded RC flexural members.

• Journal of the Korean Society of Hazard Mitigation
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• v.3 no.1 s.8
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• pp.123-131
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• 2003

An experiment was carried out to investigate the mechanical behaviour of the circular hollow section reinforced concrete member with internal corrugated steel tube. A specimen, 50cm in diameter and 340cm in length, was made and tested by 3 points bending. The test load was increased slowly (quasi static) to the failure or unacceptable deformation. During the test, lateral displacement at mid point and longitudinal displacement of extreme fiber on compressive and tensile side of the specimen were measured. The measured data were analysed and compared with calculated results for the equivalent member without inserted corrugated steel tube. The comparison shows that the flexural strength and ductility of hollow section reinforced concrete members can be improved by inserting corrugated steel tubes inside.

• Journal of the Korean Wood Science and Technology
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• v.46 no.5
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• pp.486-496
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• 2018

This study was conducted to confirm an effect of span length on bending properties of larch dimensional lumber in the four point bending test. The size of specimen in this study was 38 (width) ${\times}$ 89 (depth) ${\times}$ 3,600 (length) $mm^3$, and average air-dry density and moisture content of the specimens was $543.5kg/m^3$ and 10.5%, respectively. Visually graded No. 1 dimensional lumbers of 248 were divided by two groups to compare modulus of rupture (MOR) and modulus of elasticity (MOE). One group was tested in the four point bending test with span length of 1,650 mm, and other was tested with span length of 3,000 mm. While MOE was not different according to span length in 5% significance level, MOR was different in accordance with span lengths and was in inverse proportion to change of span length. Fifth percentiles of MOR in span length of 1,650 and 3,000 mm were 28.65 and 25.70 MPa, respectively. It was confirmed that the difference between MORs in each case increased as normalized rank increased. This is because of size effect in Weibull weakest link failure theory. Therefore, KS F 2150, in which there is only regulation about span to depth ratio of 15 or more, is needed to be revised to contain a method considering size effect for MOR. From the method, various results of bending test with different size of lumber could be used to determine design value of lumber.

• The Journal of the Korea Contents Association
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• v.18 no.11
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• pp.455-461
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• 2018

This paper presents experimental investigations about flexural strength and durability of reinforced concrete beams repaired using ductile fiber reinforced cementitious composite (DFRCC) and carbon fiber sheet through freezing and thawing test. Total 14 RC beams of $100{\times}100{\times}400mm$ size were tested by 3-point bending and freezing and thawing test by KS F 2456. The beams were reinforced using 3D10 steels on both the tensile and compressive sides, and repaired on 3 sides expect on top cycle. Test results showed that the beams repaired using fiber carbon sheet revealed about 15% higher values of flexural strength compared than the cases of DFRCC motar. On the other hand, the results did not showed meaningful differences in the aspect of durability. For further research, consideration of the steel interference effect and real old specimens such as taken from real deteriorated structures are needed to be tested after repairing with DFRCC and carbon fiber sheet.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.401-402
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• 2010

This research initially suggest flexural toughness density as a key parameter describing energy absorption capacity of High Performance Fiber Reinforced Cementitious Composites [HPFRCC] regardless of the size of specimen. Two types of high strength steel fibers, Hooked and Twisted fiber, were used in two types of flexural specimen ($100{\times}100{\times}350mm^3$ and $150{\times}150{\times}500mm^3$) to estimate and validate the flexural toughness density.