• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.4
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• pp.292-301
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• 2012

The rise in sea surface temperature (SST) as a global warming enhance overall typhoon activity. We assumed that there exist thermodynamic limits to intensity that apply in the absence of significant interaction between storms and their environment. The limit calculations depend on SST and atmospheric profiles of temperature and moisture. This approach do appear to provide resonable upper bounds on the intensities of observed storms and may even be useful for predicting the change in intensity over a long period time. The maximum storm intensities was estimated through the global warming scenarios from IPCC-AR4 report over the North-East Asia. The result shows stronger intensities according to scenarios for increase of carbon dioxide levels. And storm surge simulations was performed with the typhoons which were combined route of the typhoon Maemi (2003) and intensity as climate change scenarios. The maximum increase of storm surge heights was shown about 29~110 cm (36~65%) regionally. Especially at Masan, the result of simulated maximum surge height exceed the 200 years return period surge.

• Journal of Korean Society of Steel Construction
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• v.25 no.1
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• pp.61-70
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• 2013

A turn-buckle is capable of adjusting the tensile force by left-hand threads and right-hand threads between tension members. There are different types of turn-buckles according to tension member and connection form but the practical and existing turn-buckles are incapable of measuring the tensile force. A turn-buckle for adjusting and measuring tensile force has therefore been developed. This study shows the ultimate strength and reliability for measurement of the new turn-buckles through finite element analysis of the developed ones. From analytic results of the new turn-buckles which have the measurement limit loads of 100kN, 200kN and 300kN, the ultimate strength is approximately five times stronger than the measurement limit capacity. Additionally, a review of the new turn-buckle, which has the measurement limit load of over 300kN, shows that there is a tendency for the size of turn-buckle to become larger. So the connection devices were designed and the loading test was conducted from the concept that the parallel connection of turn-buckle with 300kN capacity can measure the tensile force of 600kN. The results of parallel loading test show the sufficient possibility. Furthermore, the mock-up test was constructed to investigate the release of initial load and corrosion when the new turn-buckle is installed at the outdoor and exposed to rain and atmosphere.

• Journal of Welding and Joining
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• v.13 no.2
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• pp.96-105
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• 1995

A modified method for the analysis of short fatigue crack growth has been presented, and calculations based upon the modified method are compared with experimental results for S45C carbon steel. It is also shown that the modified method is in good agreement with experimental data. The proposed equation for the fatigue crack growth rates includes a material constant which relates the threshold level to the endurance limit, a correction for elastic-plastic behaviour and a means for dealing with the effects of crack closure. In this study one of the modifications is to substitute the Forman' s elastic expression of the stress intensity factor range into the geometrical factor The other is a consideration of the bending effect which is developed from the moment caused by the eccentric cross sectional geometry as the crack grows. Thus, this method is useful for residual life prediction of the mechanical structures as well as the welding structures.

• Journal of Korean Association for Spatial Structures
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• v.11 no.1
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• pp.57-66
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• 2011

For the lateral load resistance of a RC frame in a medium risk seismic zone, the strength of lower story beams and columns should be larger than those of the upper stories. However, the lateral loads can be accommodated by redistributing design beam moments vertically as well as horizontally so all beams end up with identical strengths. This paper looks at the impact of the vertical redistribution of beam moments to provide identical beam strength over as many floors as possible. Two-bay six-story RC frame was designed with and without vertical beam moment redistribution and its seismic performance were evaluated by using push-over limit analysis and by non-linear time history dynamic analysis. Analytical results show that with the use of vertical beam moment redistribution the increase in the ductility demand is similar to the proportion of moment redistribution applied, but this additional demand is below the ductility capacity of well detailed RC members.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.3
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• pp.33-41
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• 2016

Concrete is inherently a good fire-resistance material among all other constrcution materials and protects the reinforcing steel inside. This study investigates the material characteristics of concrete and steel bar inside the full scale reinforced concrete(RC) beam exposed to fire test. The fire test specimen was 4 m long and the test was conducted under no loading condition following KS F 2257. Fire source is simulated by ISO 834 and number of thermocouples were installed to measure temperature variation of surfaces and inside of the beam. The measured compressive strength of cored specimen, which was exposed to fire test, was 11 MPa, about 66% lower than the strength before exposure. The yielding strength of steel bar also decreased about 75 MPa, about 17% lower. The measured temperature of protected steel bar was around $649^{\circ}C$, the critical limit, after 4 hour exposure.

• Journal of the Korean GEO-environmental Society
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• v.14 no.5
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• pp.49-56
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• 2013

The necessity of exploration in deep sea increases to develop the natural resources. The deep marine sediments, which were recovered from the hydrate occurrence regions during the Ulleung Basin Gas Hydrate Expedition 2 (UBGH2), East Sea, Korea in 2010, are explored to obtain the geotechnical characteristics and strength parameters. The index properties of the specimens including the atterberg limits, specific surface, and particle size distribution are measured and compared with the previous studies. X-ray diffraction, scanning electron microscope, and X-ray energy dispersive spectroscopy are conducted to analyze the clay mineralogy, chemical composition, and microstructure of the sediments. Strength parameters and shear wave velocities are measured with the axial strain by using an instrumented triaxial device. The strength parameters estimated by empirical equations are compared with the experimental results.

• Journal of the Korean Geotechnical Society
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• v.38 no.8
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• pp.7-15
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• 2022

Most studies have conducted cryogenic triaxial compression tests with frozen specimens prepared in a separate mold by one-directional freezing. This method has the potential to generate residual stress in a frozen specimen and cannot be adopted to simulate the application of the artificial ground freezing method in the field. Therefore, in this study, novel equipment and procedure for the cryogenic triaxial compression test were proposed to overcome the limitations of existing test methods. Therefore, the mechanical characteristics of frozen sand, considering the effect of temperature and confining pressure, were evaluated. As the freezing temperature decreased, the brittleness of frozen sand increased, and the strength increased due to a decrease in the unfrozen water content and an increase in the ice strength. A higher confining pressure resulted in an increase in interparticle friction and the pressure melting phenomenon, which caused strength reduction. Thus, it was found that the mechanical behaviors of frozen sand were simultaneously affected by both temperature and confining pressure.

• Journal of Korean Society of Steel Construction
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• v.15 no.1
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• pp.51-57
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• 2003

Current steel-framed building design codes are based on theoretical and experimental researches on the conventional structural steel. However, the yield phenomenon of austenitic stainless steel, which is characterized by continuous yielding, is quite different from that of conventional structural steel. The offset strength, which should determine the design strength, may affect the limits of width-thickness ratio of current design codes. Stub column test results showed that the limits of width-thickness ratio satisfied both ASD and LRFD codes when 0.2% offset strength was regarded as design strength. In addition, the local buckling strengths of all stainless steel stub columns did not decrease rapidly compared with those of conventional structural steel columns, even though the width-thickness ratio exceeded the design limit.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.63-63
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• 2009

최근 연비 향상 및 배기가스 저감을 위한 친환경 경량 굴삭기에 대한 연구가 활발히 진행되고 있다. 이러한 시도는 굴삭기의 소재의 강도를 490MPa급에서 700MPa급으로 고강도화를 통하여 작업장치의 경량화를 도모하고 있다. 본 연구에서는 중장비용 고강도 열연강재로 재발중인 ATOS70강재의 기본 용접성 및 GMAW 용접부 특성을 검토하였다. 사용한 시험재는 현장시험재인 14~16mmt두께의 ATOS70강재를 사용하였고, 용접경화성 및 저온균열감수성을 평가하였다. 또한 GMAW 용접을 실시하여 용접부의 이음부 특성을 검토하였다. 14mmt 두께의 ATOS70강재의 탄소당량은 약 0.44수준이고, 모재 인장강도는 약 760MPa급 수준을 보였다. 한편 최고경도시험에 의한 용접부 최도경도는 약 300Hv 수준을 보였으며, 경사 y-groove구속시험에 의한 14mmt두께의 한계예열온도는 상온이었다. 한편 GMAW 용접부 인장시험결과 740MPa급 이상의 인장강도를 확보하였고, $-5^{\circ}C$ 용접부 Charpy 충격시험결과 48J 이상의 충격인성을 나타내었다.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.1
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• pp.86-94
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• 1999

Measured shock wave effects were investigated by changing shock strength and position with particular emphasis on the stability limits of hydrogen-air jet flames. For this purpose, a supersonic nonpremixed, jet-like flame was stabilized along the axis of a Mach 2.5 wind tunnel, and wedges were mounted on the sidewall in order to interact oblique shock waves with the flame. This experiment was the first reacting flow experiment interacting with shock waves. Schilieren visualization pictures, wall static pressures, and flame stability limits were measured and compared to corresponding flames without shock-flame interaction. Substantial improvements in the flame stability limits were achieved by properly interacting the shock waves with the flameholding recirculation zone. The reason for the significant improvement in flame stability limits is believed to be the adverse pressure gradient caused by the shock, which can elongate the recirculation zone.