• Journal of the Korean Society of Safety
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• v.31 no.6
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• pp.6-11
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• 2016

CFRP composite laminates are widely used as structural materials for airplanes, automobile and aerospace vehicles because of their high strength and stiffness. This study aims to examine an effect of curvature on the penetration fracture characteristic of an orthotropic composite laminated shell. For the purpose, we manufactured orthotropic CFRP shell specimen with different curvatures, and conducted a penetration test using an air-gun. Those specimens were prepared to varied curvature radius(${\infty}$, 200mm, 150mm and 100mm)and were stacked to $[O^{\circ}{_3}/90^{\circ}{_3}]_s$. When the specimen is subjected to transverse impact by a steel sphere(${\Phi}10$), the velocity of steel sphere was measured both before and after impact by determining the time for it to pass two ball-screen sensors located a known distance apart. As the curvature increases, the absorption energy and the critical penetration energy increased linearly because the resistance to the bending moment. Patterns of cracks caused by the penetration of CFRP laminated shells included fiber breakage, lamina fracture, matrix crack interlaminar crack and intralaminar crack.

• Proceedings of the KSR Conference
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• 2001.10a
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• pp.558-561
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• 2001

SIP(Soil cement Injected Precast pile) that inserts a precast pile after injecting a cement paste into a boring has been applied rapidly through the change of construction circumstances. But there isnt any logical equation of a bearing capacity fitted to SIP yet. So Meyerhof equation has mainly been used to predict a bearing capacity in a design stage instead. But it has shortcomings such as lack of confidence because it has derived not from a theory but from an experience obtained from the result of SPT (Standard Penetration Test) and because a penetration depth tends to be deeper by an excessive design that depends on an end bearing capacity of a pile more than a skin frictional resistance. In this study, thereupon, a direct shear test in the laboratory was performed to both SM and SC soils in variable conditions to verify skin friction properties for the purpose of presenting some reasons capable of reducing penetration depths. Through the tests, soil to soil of SM in cohesion, rough panel to soil of SM in friction angle and soil to soil of SM in shear strength tended to be high. And a shear strength increased as its total unit weight increased in all cases.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.4
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• pp.113-120
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• 2005

In order to investigate the characteristics of penatration and the effect of surface treatment in A15052-H34, Al5082-Hl31 and titanium alloy laminates which were treated by anodizing and PVD(Physical Vapor Desposition) method, ballistic tests were conducted. Thickness of surface membrane in A15052-H34, Al5082-Hl31, were $25{\mu}m$ and that of titanium $0.9{\mu}m$ respectively. Surface hardness test was conducted using micro Vicker's hardness tester. Resistance to penetration is determined by the protection ballistic limit(V50), a statistical velocity with $50\%$ probability for complete penetration. Fracture behaviors and ballistic tolerance, described by penetration modes, are observed from the results of V50 test and Projectile Through Plate(PTP) test at velocities greater than protection ballistic limit, respectively. Present experimental results derived from this research help to optimize laminate impact behavior by varing the laminate thickness and surface treated materials.

• Journal of the Korea Concrete Institute
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• v.16 no.4 s.82
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• pp.485-492
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• 2004

In this study, ASTM C 1202 which is most commonly used for evaluating the penetration resistance into the concrete is reviewed. The test results by ASTM C 1202 showed that the passed charge could be underestimated as the $OH^-$ ion concentration in the concrete is lowered when the concrete is mixed with the admixtures. Therefore, the modified method using the distilled water was proposed in the paper. According to the test results, the modified method is not susceptible to $OH^-$ ion and temperature rise. In addition, the long term emersion test for the concrete mixed with the admixtures in the NaCl solution showed that the chloride diffusion coefficient tested by the modified method have higher correlation compared to the conventional ASTM method.

• Journal of the Korea Institute of Building Construction
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• v.11 no.2
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• pp.189-199
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• 2011

Installation of a proper root barrier in a green roof system is very important in order to protect the concrete slab of roof and the root penetration in the waterproofing layer. To select the proper root barrier materials and methods, it is necessary to understand the environmental conditions affecting the waterproofing-root barrier system in green roof construction site. Therefore, we suggested as the environmental performance indexes four kinds of performance requirements; root penetration, chemical attack by chemical agent or fertilizer, load impact by soil depth and size of plant, and water pressure. The related four test methods were suggested for the inspection of these performance indexes. In this research, we could suggest for kinds of test methods as standard test methods to evaluate the environmental performance of waterproofing-root barrier for greening roof system.

• Journal of the Korean Geotechnical Society
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• v.22 no.10
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• pp.55-67
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• 2006

Modern methods for designing IGM(Intermediate Geomaterial) socketed drilled shafts require knowledge of the compressive strength and modulus of the IGM. However, the weathered IGMs at many sites prohibit the recovery of samples of sufficient length and integrity to test cores in either unconfined or triaxial compression tests. Since rational design procedures usually require values of compressive strength, surrogate methods must be employed to estimate the compressive strength of the IGM. A surrogate method considered in this study was Texas cone penetrometer tests which were performed at several sites in North Central Texas. Correlations of Texas cone penetrometer tests and compressive strengths of cores from these formations are provided in the paper. In order to develop the relationships between Texas cone penetrations and side and base resistance of IGM socketed drilled shafts, three filed load tests were conducted in the same sites. Based on the field study and literature reviews, a design method for IGM socketed drilled shafts using Texas cone penetration test was proposed.

• Structural Engineering and Mechanics
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• v.47 no.5
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• pp.701-711
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• 2013

People started to replace natural aggregate with recycled aggregate for a number of years due to disposal problem and certain other potential benefits. Though there are number of drawbacks with use of recycled aggregates like lesser modulus of elasticity, low compressive strength, increase in shrinkage, there are results of earlier studies that use of chemical and mineral admixtures improves the strength and durability of recycled concrete. The use of recycled aggregate from construction and demolition wastes is showing prospective application in construction as alternative to natural aggregates. It conserves lot of natural resources and reduces the space required for the landfill disposal. In the present research work, the effect of recycled aggregate on strength and durability aspects of concrete is studied. Grade of concrete chosen for the present work is M50 (with a characteristic compressive strength of 50 MPa). The recycled aggregates were collected from demolished structure with 20 years of age. Natural Aggregate (NA) was replaced with Recycled Aggregate (RA) in different percentages such as 25, 50 and 100 to understand its effect. The experiments were conducted for different ages of concrete such as 7, 14, 28, 56 days to assess the compressive and tensile strength. Durability characteristics of recycled aggregate concrete were studied with Rapid chloride penetration test (as per ASTMC1202), sorptivity test and acid test to assess resistance against chloride ion penetration, capillary suction and chemical attack respectively. Mix design for 50 MPa gives around 35 MPa after replacing natural aggregate with recycled aggregate in concrete mix and the chloride penetration range also lies in moderate limit. Hence it is understood from the results that replacement of NA with RA is very much possible and will be ecofriendly.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.269-281
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• 2010

The cone penetration test(CPT) has been increasingly used for in situ site characterization. However, the use of CPT is often limited due to specific site conditions depending on the cone size, geometry, and capacity of the CPT system used. In South Korea, it has generally been considered that the CPT could be satisfactorily performed only in soft soils. Louisiana State University/ Louisiana Transportation Research Center has implemented a field-rugged continuous intrusion miniature cone penetration test (CIMCPT) system since the 1990s. The miniature cone penetrometer of the CIMCPT system has a cross-sectional cone area of $2cm^2$ allowing finer soil profiles compared to the standard $10cm^2$. The reduced cross-sectional area also enables a system capacity reduction leading to cost saving and ease in maintenance. In addition, the continuous intrusion mechanism allows fast and economic site investigations. Samsung C&T Corporation has recently implemented a similar CIMCPT system. In this study, case studies on the field application of Samsung CIMCPT system for the last 2 years are presented to illustrate its performance investigation and its usefulness and limitation. Results of the case studies show that the CIMCPT system can be applied to soils with cone tip resistance($q_c$) values up to about 30MPa and allows a reliable and useful way to characterize soft soils. The results also show that the rod buckling limits the investigation depth by the system and the large contact pressure of the CIMCPT truck prevents the use of the system at sites with soft surface soils. According to the results of the case studies, the Samsung CIMCPT system has been being upgraded with a miniature cone with a longer rod, a crawler-type transportation system, a pre-boring system, and so on.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.301-302
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• 2023

In this study, we aimed to identify changes in fire resistance according to the type of sleeves used for pipe penetrations and to examine their accreditation of fire resistance performance and use them as basic data. The test results of fire resistance according to the type of sleeve used in non-metallic pipe facilities showed that the temperature on the support side was higher for sleeves with higher thermal conductivity. For the temperature on the surface of the pipes, in the case of galvanized steel plates, steel pipes, and structures without sleeves, the highest temperature was observed after the expansion of the firestop material for 46 to 53 minutes and then decreased. PVC sleeves showed a steady increase in temperature until 53 minutes, after which the temperature did not increase further. In addition, for non-metallic pipes, the effect of the type of sleeve on fire resistance is considered to be insignificant because the lower part (heating direction of the furnace) under the support structure is cut off to block the heat during the two-hour fire resistance test.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.141-142
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• 2002

In this paper, we propose a slurry jet (water containing $1\;{\mu}m$ alumina particles) impact test in order to quickly evaluate the wear properties of physical vapor deposited (PVD) coatings on commercial cutting tools. Linear wear was obtained for bothe coating and substrate material, and the penetration through the coating into the substrate was signified by a sharp increase in slope of the wear versus time curve. The PVD coatings deposited on the tools showed the same wear rates as those on reference plate specimens produced by the same coating methods. We conclude that our proposed evaluation technique for coatings is considerably useful as a screening test when evaluating coated tools like twist drills, taps, end mills, gear hobs, etc.