• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.3
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• pp.161-175
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• 1985

The simplified method drawing the S-N curves in welding joints of the cover plates, the transverse stiffners and the gusset plates of the plate girders by calculation and its computer program without the direct fatigue tests, was established. And the method was applied to the Young- Dong Great Bridge, the 3 th Han River Bridge and the Kang Chon Bridge. Before this, SS 41, SS 50, SWS 50 and SWS 58 were selected, then the compact tension specimens were made by the use of these materials, the things welded by these materials transversely and the ones longitudinally to the crack propagation direction. The fatigue tests were performed by the use of these 'specimens, and the values of material constants c and m were obtained. By these results the followings were obtained. It was showed that the fatigue: strength in the case of the cover plates was much lower than in the case of other two cases. It was showed that, in the case of the cover plates with the cover plates thicker the fatigue strength was lower, but besides this the fatigue strength was not much influenced by the size of specimens. It was showed that in the difference from this the fatigue strength was sensitively influenced by the values of c and m. It was showed that in accordance with the lower values of c and m the fatigue strength was fairly higher, in accordance with the lower values of m the gradient of the S-N curves was abrupter. It was considered that if such data were accumulated continuously, in the near future the basic pattern used availably in providing the indicater of the fatigue design of the plate girders, and presuming the life-proof of the existing plate girders.

• Journal of the Korea Concrete Institute
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• v.24 no.3
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• pp.225-232
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• 2012

This paper presents the test results on the shear performance of large-size reinforced concrete beams using recycled fine aggregate to evaluate its applicability to structural concrete. The performance of these beams is compared to that of similar beams casted with natural coarse and fine aggregates. All of the beam specimens without shear reinforcement had $400mm{\times}600mm$ rectangular cross section and a shear span ratio (a/d) of 5.0. Five concrete mixtures with different replacement levels of recycled fine aggregates (0, 30, 60, 70 and 100%) were used to obtain a nominal concrete compressive strength of 28MPa. The test results of load-deflection curve, shear deformation, diagonal cracking load, crack pattern, ultimate shear strength, and failure mode are examined and compared. In addition, code and empirical equations from KCI, JSCE, CSA, Zsutty, and MCFT were considered to evaluate the applicability of these equations for predicting shear strength of reinforced concrete beam with recycled fine aggregate. The results showed that the overall shear behavior of reinforced concrete beams incorporating less than 60% recycled fine aggregate was comparable with that of conventional concrete beam. The MCFT gave good prediction and other code equations were conservative in predicting the shear strength of the tested beams. The beam specimens with replacement of 70 and 100% of natural fine aggregates by recycled fine aggregates showed different failure mode than other tested beams.

• The Journal of Engineering Geology
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• v.12 no.2
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• pp.137-150
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• 2002

Recently, plane failure mode occurred frequently along the bedding plane having low angle dip about 20 degree when cutting slopes were constructed in sedimentary rock region of the Gyeongsang Basin. Landslide of the Whangryeong Mountain which was occurred at Busan Metropolitan City in 1999 belongs to the category mentioned above. Reconstruction for cutting slope of the Whangryeong Mountain has finished in 2000 and final grade of reconstructed cutting slope is 1:2.0. To analyze slope failure mode for landslide of the Whangryeong Mountain, various analyses were performed such as in-situ investigation and test, drilling, laboratory test, aerial photograph interpretation, X-ray diffraction analysis, and slope stability analysis using Stereographic Projection and Limit Equilibrium methods. As the result, it is identified that tension cracks had been developed one year before the landslide took place. The tension crack semis to be formed by merging several joint sets. It appears that failure blocks broke down along the sliding planes of different layers. Risk of plane failure is conformed as a result of stability analysis using Stereographic Projection and Limit Equilibrium methods in case that greenish gray tuffaceous shales, regared as sliding planes, are weathered. From now on, a detailed investigation is needed for the thin layers which is sensitive to weathering, and stability analysis for this layer is performed at cut slope construction site having similar geological condition.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.2
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• pp.243-260
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• 2018

A literature review on the effects of high temperature and radiation on radiation shielding concrete in Spent Fuel Dry Storage is presented in this study with a focus on concrete degradation. The general threshold is $95^{\circ}C$ for preventing long-term degradation from high temperature, and it is suggested that the temperature gradient should be less than $60^{\circ}C$ to avoid crack generation in concrete structures. The amount of damage depends on the characteristics of the concrete mixture, and increases with the temperature and exposure time. The tensile strength of concrete is more susceptible than the compressive strength to degradation due to high temperature. Nuclear heating from radiation can be neglected under an incident energy flux density of $10^{10}MeV{\cdot}cm^{-2}{\cdot}s^{-1}$. Neutron radiation of >$10^{19}n{\cdot}cm^{-2}$ or an integrated dose of gamma radiation exceeding $10^{10}$ rads can cause a reduction in the compressive and tensile strengths and the elastic moduli. When concrete is highly irradiated, changes in the mechanical properties are primarily caused by variation in water content resulting from high temperature, volume expansion, and crack generation. It is necessary to fully utilize previous research for effective technology development and licensing of a Korean dry storage system. This study can serve as important baseline data for developing domestic technology with regard to concrete casks of an SF (Spent Fuel) dry storage system.

• The Korean Journal of Petroleum Geology
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• v.14 no.1
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• pp.36-44
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• 2008

Natural gas in tight reservoirs, one of unconventional hydrocarbon resources, has become a significant exploration and exploitation targets. Tight gas reservoirs are the gas-bearing rocks that commonly have a permeability of less than 0.1 millidarcy (mD). Tight gas reservoirs are characterized by extensive and deep locations as well as abnormal pressure such as over- or under-pressure. The tight gas reservoirs are independent of structural or stratigraphic traps, whereas conventional gases normally occur at these traps. Tight gas reservoirs can be productive when stimulated by hydraulic fracturing. Better production areas within the tight reservoir beds are referred to as sweet spots that are commonly caused by natural fractures, which should be understood and identified to enhance the recovery of the gas from tight reservoirs. The exploration and production techniques allow the commercial production of tight gas, one of environmentally friendly resources. Slant and horizontal wells have best production when they intersect the fractures. Gas production from the tight reservoirs has rapidly grown in U.S. and Canada. Indeed, the U.S. gas production of tight sandstones increases from 11.1% in 1990 to 24.1% in 2005. The presence of tight gas reservoirs has been suggested on the Korean offshore block 6-1. Paradigm shift from conventional to unconventional tight reservoir is required to develop the tight gas from the block.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.5
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• pp.111-117
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• 2019

Shear experiments were carried out to evaluate shear performance of SFRC deep beams with end-anchorage of SD600 high strength headed reinforcing tensile bars. The experimental variables include the end-anchorage methods of tensile bars (headed bar, straight bar), the end-anchorage lengths, and the presence of shear reinforcement. Specimens with a shear span ratio of 1 showed a pattern of the shear compression failure with the slope cracks progressed after the initial bending crack occurred. Specimens with end-anchorage of headed bars (H-specimens) showed a larger shear strengths of 5.6% to 22.4% compared to straight bars (NH-specimens). For H-specimens, bearing stress reached 0.9 to 17.2% of the total stress of tensile bars up to 75% of the maximum load, and reached 22.4% to 46%. This shows that the anchorage strength due to the bearing stress of headed bars has a significant effect on shear strength. The experimental shear strength was 2.68 to 4.65 times the theoretical shear strength by the practical method, and the practical method was evaluated as the safety side.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1C
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• pp.33-42
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• 2006

Lots of river embankments or levees in Korea are quite so old and unknown the origin even. The river deposits, moreover, obtainable easily somewhere were used for materials of embankment without any technical considerations such as the influence soil properties and construction methods on embankment stability. It's natural that safety would be threatened if the water level rises due to flood or rainfall when it comes to abnormal weather conditions, especially. From this point of view, enlargement of embankment, irrigation works, etc. are in progress recently at the situation from a reinforcement work. However, taking influence of soil properties and construction methods on embankment stability into account against cracking or piping is still insufficient. Fragmentary design criteria or irrational construction methods are applied rather as the case may be. In this study, therefore, a way to estimate piping and cracking resistance (Sherard, 1953) has been introduced and reevaluated for practical use with an eye to material properties and its applicability to piping-experienced embankments was examined. Piping possibility was also examined in the present design criteria and compared. In view of the results achieved, it reflects that both yield piping possibility. But it's still necessary to complement how to judge and verify piping resistance of given soils with gradation curves by the representative curve, quantitatively and that piping resistance should consider compaction effects as well.

• Journal of Conservation Science
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• v.33 no.6
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• pp.399-416
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• 2017

The 'Wat Phou and Associated Ancient Settlements within the Champasak Cultural Landscape' of Laos was designated as a UNESCO World Cultural Heritage in 2001. The uppermost structure of the Sanctuary in Wat Phou has been destroyed and being variably damaged, maintenance is required through scientific and systematic diagnosis. The Sanctuary of Wat Phou was constructed mainly using sandstones and bricks. There are physical damages including fracture, break out, exfoliation and interval as well as biological damages by lichen, mosses and weeds. According to the ultrasonic velocity measurement and property evaluation of the sandstones of the Sanctuary in Wat Phou, weathering index of the eastern side sandstones is 0.10 to 0.74 (mean 0.36), showing MW grade. Southern and northern side sandstones have relatively higher properties with average weathering indices of 0.30 and 0.32. The results of slope analysis of the Sanctuary, indicated that the 4th spot in the southern side has the largest slope of $5^{\circ}W$, seemingly due to the unstable ground around the Sanctuary. Based on the relative level measurement and past drawings, the Sanctuary is verified to have been located on ground with a certain slope rather than flatland. The ground of the southern side is inclined $1.51^{\circ}$ more than that of the northern side, which will affect the structural stability of the temple. The interval width of the selected southern spot is the largest with an average width of 159.5 mm, and the largest width is 328.3 mm at the top, since the width increases above rather than below, seemingly due to the unequal subsidence of the ground. Constant maintenance for conservation is required for the structural stability of the Sanctuary in Wat Phou, which was partly collapsed and has also suffered physical damage.

• Journal of the Korean Geophysical Society
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• v.7 no.3
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• pp.193-206
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• 2004

Geophysical data including chirp (3 7 kHz) subbottom profile and detailed bathymetry were obtained over three seamounts in the Ogasawara Fracture Zone (OFZ) of the western Pacific, as a part of manganese crust survey onboard R/V Onnuri in 2003. The OFZ is a 150-km-wide, 600-km-long rift zone, which separates the East Mariana and Pigafetta Basin. The OFZ is unique in that it includes many seamounts (e.g., Magellan Seamounts andseamounts on the Dutton Ridge). The sub-seafloor acoustic echoes obtained near the OFZ were classified into following types on the basis of their characteristics: types I-1(pelagic sediment with parallel or subparallel reflectors), I-2 (pelagic sediment with no internal reflectors), and III-1 (reef build-up complex) on summit; types II-1 and III-2 (basement outcrop) on flank rift zone and upper slope, respectively; type III-3 (slump) on the lower slope and embayment between the flank rift zones; types II-2 (debrite) on the base of slope and basin floor; and types II-3 (turbidite or pelagic sediment) and II-4 (turbidite) on the basin floor. The mass-wasting that produced the complex of type II-2 debrite and III-3 slump on the lower slope and basin may have been caused by (1) strong tensional stress in the OFZ which may cause the numerous fissures or basement faults and (2) complex of the faults on the summit and steep upper slope. The variations in the echo type of pelagic sediment in the summit of seamounts may be related with the changes in the depositional and/or erosional environments. Type I-2 pelagic sediment, which is characterized by a thin and intermittent coverage, was probably deposited at a sheltered area when the current was strong, whereas type I-1 pelagic deposit occurred during a stage of progressive sedimentation.

• The Journal of Engineering Geology
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• v.10 no.3
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• pp.205-216
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• 2000

An unstable natural slope located at Icheon-Ri, Dasa-Eup, Dalseong-Kun which has been severely cracked during heavy rain fall in September, 1998, was investigated and analysed for remedial measures. Various geological data were obtained by performing a surface geological survey, a ground penetrating radar(GPR) exploration, four geotechnical borings with field and laboratory tests, and the precipitation records were also reviewed. Based on the these data, the probable sliding plane was determined as a bedding plane with dip angle of 20 to 25 degrees between sandstone and shale layers at depth of 6 to 8 meters. By performing back analyses with the limit equilibrium method, the friction angle and cohesion of the sliding plane were determined as 18$^{\circ}$ and 0, respectively. Based on these results, a series of stability analyses such as stereo-graphic projection method, limiting equilibrium method and numerical method were carried out. The remedial measures for the unstable slope were selected based on the results of the limit equilibrium analyses by considering various conditions expected at the site. Ground grouting or anchoring method with proper surface drainage systems could be employed for the long term safety of the slope.