• Proceedings of the KWS Conference
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• 2010.05a
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• pp.63-63
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• 2010

The pre-heat free consumables for GMAW, SAW and FCAW processes that matches the Cu-bearing PFS-700 steel which has yield strength over 700MPa were developed and evaluated to see the suitability in military such as submarine and battle ship. Explosion bulge test in underwater was developed and applied to see the reliability of welded structure. All welding was conducted without pre-heat before welding, the interpass temperature was below $150^{\circ}C$ for all welding conditions. Tensile strength for the weld metal in GMAW, SAW and FCAW process is 887MPa, 875MPa and 813MPa, respectively, these values are similar to the base metal of PFS-700 steel of 838MPa. EBT results in GMAW, SAW and FCAW show 14.0%, 14.02% and 15.9% reduction of thickness without generation of crack, respectively and stand-off distance was set up properly to have over 14.0% reduction of thickness. Through EBT results, the developed new consumables are applicable to the weapon systems such as submarine and battle ship.

• International Journal of Highway Engineering
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• v.3 no.2 s.8
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• pp.103-112
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• 2001

This study was performed to evaluate applicability of recycled aggregates as subbase and surface concrete materials for cement concrete pavement. Laboratory compaction test, CBR test and plate load bearing test were conducted to evaluate applicability for pavement subbase materials. Recycled concrete for surface course was manufactured with a design strength of $280kgf/cm^2$. Normal coarse aggregate was substituted with recycled aggregates with five different ratios, 0%, 20%, 40%, 60% and 80% for recycled concrete mixes. Fresh concrete Properties, concrete strength properties for the five substitution percentages of recycled aggregates after 28-day curing and freezing-and-thawing resistance were evaluated experimentally. Based on the experimental results, it was concluded that the recycled aggregate was the material good enough to use for subbase material, and 40% or lower substitution ratio was an appropriate percentage of recycled aggregates replacement for surface concrete.

• The Korean Journal of Mycology
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• v.13 no.3
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• pp.179-183
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• 1985

Cylindrocarpon spp. were isolated from the soil where strawberry was grown in Suweon by soil plate method: colonies reaching 10 mm diam. in seven days at about $20^{\circ}C$; sporodochia with cream to beige to conidial slime commonly produced; conidiophore repeatedly branched and bearing subulate phialides; macroconidia cylindrical in the center part, straight or slightly curved and mostly $1{\sim}3\;septate,\;22{\sim}45\;{\times}\;5.0{\sim}6.0\;{\mu}m$; chlamydospore abundantly produced, intercalary or terminal on mycelium, singly or in chains and smooth or warted. The hypha and spore were easily fused each other on water agar. This fungus was pathogenic strawberry as a result of inoculation test. The symptom showed dwarf and yellowing at top and rotted roots under the ground. The fungus was identified as Cylindrocarpon destructans Scholten from the shape of conidiophores and conidia, mycelial growth and pathogenicity test.

• International Journal of Highway Engineering
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• v.14 no.3
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• pp.49-58
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• 2012

In many countries including Korea, the design concept of pavement structure has been converted from empirical method to mechanisticempirical method since the advent of compaction control based on resilient modulus proposed by AASHTO in 1986. Studies of last decades indicates that the classical compaction control method based on relative compaction and plate bearing test(PBT) will necessarily move to the methods taking advantage of light falling weight deflectometer(LFWD) and dynamic cone penetrometer(DCP) in addition to PBT. In this study, the validity of resilient modulus prediction equation proposed by Korean Pavement Design Guide is verified by comparison with physical properties of subgrade soil and the results of structural analysis. In addition, correlational equations between elastic modulus measured by various field tests and resilient modulus estimated by empirical model are proposed. Finally, a field test-based compaction control procedure for subgrade is suggested by using proposed correlational equations.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.6
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• pp.197-204
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• 2006

Recently, in order to realization of construction and economical saving, various studies are progressing. Also, the study on RCS system which is consisted of reinforced concrete column and steel beam is progressing actively. Actually, however, resisting mechanism of panel zone is influenced by transverse beams when the stress transfers inner panel to outer panel but existing literature didn't reflect the effect of transverse beams. This paper is to analyze the test result of five inner beam-column joints specimen with a variable such as web, flange thickness of transverse beam and face bearing plate(FBP) for RCS systems were tested under cyclic loadings conforming to NEHRP recommendation to investigate the effect of transverse beams and the structural performance of beam-column joints. From the test result, it was shown that transverse beams are effective to enhance the shear strength and structural performance of beam-column joints.

• Journal of the Korean GEO-environmental Society
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• v.14 no.12
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• pp.23-30
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• 2013

Bearing capacity of pile is governed by only skin friction in frozen ground condition, while it is generally governed both by skin friction and end bearing capacity in typically unfrozen ground condition. Skin friction force, which arises from the interaction between pile and frozen soils, is defined as adfreeze bond strength, and adfreeze bond strength is one of the most important key parameters for design of pile in frozen soils. Many studies have been carried out in order to analyze adfreeze bond strength characteristics over the last fifty years. However, many studies for adfreeze bond strength have been conducted with limited circumstances, since adfreeze bond strength is sensitively affected by various influence factors such as intrinsic material properties, pile surface roughness, and externally imposed testing conditions. In this study, direct shear test is carried out inside of large-scaled freezing chamber in order to analyze the adfreeze bond strength characteristics with varying freezing temperature and normal stress. Also, the relationship between adfreeze bond strength and shear strength of the frozen soil obtained from previous study was analyzed. The coefficient of adfreeze bond strength was evaluated in order to predict adfreeze bond strength based on shear strength, and coefficients suggested from this and previous studies were compared.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.40 no.5
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• pp.421-428
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• 2022

The earthwork is a core process of all constructions, and compaction measurement of earthwork play an important role in improving productivity. The analog tests such as Plate Bearing Test and Sand-cone occupy current compaction measurement techniques. Due to advanced 4th Industrial Revolution, research on analog tests combined smart construction technology are actively conducted. DCPT (Dynamic Cone penetration Test), simpler and faster than conventional tests, has recently on rise. However, it is also an analog that measures data manually and has several disadvantages such as history management and data verification. The IoT-based DCPT system developed in this study combines digital wire sensors, mobile phones, and Bluetooth with conventional DCPT. Compare to conventional test methods, IoT-based DCPT has advantages such as performance time, single-person measurement, low cost, mobile-based management, and real-time data verification. In addition, a test bed was built to verify IoT-based DCPT. The test bed was built under similar conditions to the actual earthworks site through roller equipment. DCPT data obtained from 322 stations. As a result, IoT-based DCPT showed good performance, and the test bed was also showed stable results as the compaction was carried out.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.5
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• pp.32-39
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• 2021

Recently, necessities of steel form for reinforced concrete beam and girder have been emphasized in building structures for the reduction of the construction period and the labor cost. SY Beam was developed for the these purposes and is roll-formed using thin steel plate. On this research, we tried to evaluate and verify the performance and behavior of SY Beam under construction loading stage as like pouring in situ concrete. For the standard shape of SY beam, structural modelling with various steel thicknesses has carried out using MIDAS GEN program. From results of modelling, the width and height of SY Beam were determined 600mm and 400mm respectively. For 3 SY Beams, the loading experiment was performed to measure vertical and horizontal displacement under stacking sand, concrete block, and bundle of rebar. As a result, the vertical deflection showed a tendency to decrease as the thickness increased. In the horizontal displacement, the trend according to the thickness was not clearly observed. From the evaluation on the loading experiment, it is considered that the SY Beam can secure both workability and structural safety. In particular, the SY Beam(1.2mm) hardly generates horizontal displacement, so it has excellent load-bearing capacity. So, we judged that the SY Beam with 1.2mm steel plate has excellent performance and consider to be immediately commercially available.

• Journal of the Korean GEO-environmental Society
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• v.19 no.11
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• pp.5-14
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• 2018

Worldwide, soil compaction work is one of the most important activities that are carried out on civil engineering works sites. Compaction work, particularly in the area of road construction, is considered to be important, as poor compaction work is closely related with poor construction even after a construction is complete. Currently, the plate bearing test or the sand cone method relative to the unit weight of soil test are commonly used to measure the degree of compaction, but as these require a great deal of time, equipment and manpower, it is difficult to secure economic efficiency. The method that is used to measure the degree of compaction according to the penetration depth achieved by free fall objects through gravity is the Free-Fall Penetration Test (FFPT), which uses a so-called "portable compaction measuring meter (PCMM)." In this study, the degree of compaction was measured and a penetration depth graph was developed after the field test using the portable compaction measuring meter. The coefficient of determination was 0.963 at a drop height of 10 cm, showing the highest level of accuracy. Both horizontal axis and longitudinal axis were developed in a decimal form of graph, and the range of allowable error was ${\pm}1.28mm$ based on the penetration depth. The portable compaction measuring meter makes it possible to measure the degree of compaction simply, quickly and accurately in the field, which will ensure economic efficiency and facilitate the process management.

• Journal of the Korean Geotechnical Society
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• v.36 no.12
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• pp.45-56
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• 2020

In this paper, intelligent compaction (IC) technology and the earthwork quality control specifications based on IC were analyzed, and the field study was conducted to investigate the relationship between the representative IC value CMV (Compaction Meter Value) and spot test results (plate bearing test and field density test). As the number of roller passes increased, both the CMV and spot test results increased. However, point-by-point comparison between CMV and spot test results yielded poor quality correlations; this is because the ununiform stiffness of the underlying layer and the moisture content of the lift layer affected the CMV and spot test results, respectively. Most international specifications related to IC requires knowledge of the IC values and their relationships with the soil properties obtained by the traditional spot tests. Therefore, for the successful implementation of intelligent compaction technology into earthwork construction practice, the number of roller passes as well as the lift thickness and the moisture content of the soil should be carefully considered.