• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1455-1462
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• 2010

PHE (Process Heat Exchanger) is a key component required to transfer heat energy of $950^{\circ}C$ generated in a VHTR (Very High Temperature Reactor) to the chemical reaction that yields a large quantity of hydrogen. Korea Atomic Energy Research Institute established the helium gas loop for the performance test of components, which are used in the VHTR, and they manufactured a PHE prototype to be tested in the loop. In this study, as part of the hightemperature structural-integrity evaluation of the PHE prototype, which is scheduled to be tested in the helium gas loop, we carried out high-temperature structural-analysis modeling, thermal analysis, and thermal expansion analysis of the PHE prototype. The results obtained in this study will be used to design the performance test setup for the PHE prototype.

• Science of Emotion and Sensibility
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• v.14 no.2
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• pp.191-196
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• 2011

Fabric extraction force measured through nozzle tester reflects a comprehensive fabric handle. Nozzle tester takes advantage of low cost, and simple and fast operating procedure compared with KES system. The paper is to develop the semi-emprical equation for assessment of the fabric handle measured with nozzle tester on the basis of friction law. The variables considered in the equation arc fabric's frictional coefficient and drape coefficient which is determined in terms of fabric bending length and shear strain. The experiment of 12 different cotton and polyester fabrics and comparisons between experimental and theoretical results were conducted. Fabrics of high frictional coefficients, high bending length, and low shear strain showed high fabric handle forces (low handle values). The handle forces predicted from the equation agreed well with those measured, which indicates that the equation can be used to objectively evaluate fabric handle with respect to fabric's own properties and also provide an information for fabric design to improve the handle performance.

• Journal of the Korean Society for Railway
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• v.17 no.1
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• pp.43-51
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• 2014

In the earth structures of railways, large coarse granular materials are widely used as fill materials. However, experimental studies that consider the dynamic properties of these coarse granular materials have rarely been carried out in Korea due to the lack of a large scale test apparatus in this country. In this study, large scale cyclic triaxial tests were carried out for materials such as reinforced roadbed (subballast, graded crushed stone), transition zone gravel, and the upper subgrade of a railway. These specimens were prepared according to certain conditions (dry unit weight, grain size distribution, and so on) specified in the Korea railroad design standard. Based on these large triaxial test results, normalized shear modulus and damping ratio curves according to small strain level are suggested. A model and coefficients for each material are also proposed.

• The Journal of Engineering Geology
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• v.22 no.3
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• pp.293-307
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• 2012

Shear wave velocity is commonly invoked in explaining geophysical phenomena and in solving geotechnical engineering problems. In particular, the importance of shear wave velocity in geotechnical earthquake engineering has been widely recognized for seismic design and seismic performance evaluation. In the present study, various insitu seismic tests were performed to evaluate geotechnical dynamic characteristics at 183 sites in Korea, and shear wave velocity profiles with depth were determined to be representative of the dynamic properties at the investigated sites. Subsurface soil and rock layers at the target sites were reclassified into five geotechnical layers: fill, alluvial soil, weathered soil, weathered rock, and bedrock, taking into account their general uses in geotechnical earthquake engineering practice. Average shear wave velocity profiles for the five geotechnical layers were obtained by synthesizing the shear wave velocity profiles from seismic tests in the field. Based on the profiles, a representative shear wave velocity value was determined for each layer, for use in engineering seismology and geotechnical earthquake engineering.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.4
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• pp.385-391
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• 2014

A wheeled armored vehicle is a military vehicle that has been developed to enhance combat capabilities and mobility for the army. The wheeled armored vehicle has a high center of gravity, and it operates on unpaved and sloped roads. Therefore, this vehicle has a high risk of rollover crashes. To design the interior of the military vehicle, the crew's safety during rollover crashes is an important factor. However, actual vehicle tests for design are extremely expensive. In this paper, nonlinear dynamic analysis is performed to simulate the rollover crashes and the passenger injury is assessed for a wheeled armored vehicle. The scope of this research is the rollover condition, FE modeling of the wheeled armored vehicle and the dummy, arrangement of dummies, assessment of passenger injuries, and simulation model for rollover crashes.

• KEPCO Journal on Electric Power and Energy
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• v.6 no.2
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• pp.163-171
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• 2020

A model test for assessment of towing stability and seakeeping of a multi-purpose mobile base (MMB) was performed in calm water and wave conditions. Scale ratio of the MMB was 1/48. Tension of the towing line was measured during tests to estimate effective power to tow the full scale MMB. The tests were repeated with towing speed. In addition, an inertial measurement unit was used to measure six DOF motion of the model. Seakeeping performance was assessed through the captive model test.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.2
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• pp.191-200
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• 2011

A PHE (Process Heat Exchanger) is a key component of nuclear hydrogen system for massive production of hydrogen; the PHE transfers the very high temperature heat ($950^{\circ}C$) generated from the VHTR (Very High Temperature Reactor) to a chemical reaction. The Korea Atomic Energy Research Institute developed a small-scale gas loop for testing the performance of VHTR components and manufactured a modified PHE prototype for carrying out the testing in the gas loop. In this study, as a part of the evaluation of the high-temperature structural integrity of the modified PHE prototype which is scheduled to test in the gas loop, we carried out high-temperature structural analysis modeling, macroscopic thermal and structural analysis of the PHE prototype under the gas loop test conditions as a precedent study before carrying out the performance test in the gas loop. The results obtained in this study will be used to design the performance test setup for the modified PHE prototype.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2C
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• pp.125-131
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• 2008

Ground stiffness(shear wave velocity) is one of the key parameters in geotechnical earthquake engineering. An In-situ seismic technique has its own advantages and disadvantages over the others in stiffness measurements. By combining the crosshole and seismic cone techniques and utilizing favourable features of bender elements, a new hybrid probe has been developed in order to enhance data quality and easiness of testing. The basic structure of the probe, called "MudFork" is a fork composed of two blades, on each of which source and receiver bender elements were mounted respectively. To evaluate the disturbance caused by the penetration of the probe, shear wave velocity measurements were carried out in the Kaolinite slurry in the laboratory. Finally, the probe was penetrated in coastal mud near Incheon, Korea, using SPT(standard penetration test)rods pushed with a routine boring machine and shear wave velocity measurements were carried out. The results were verified with data from laboratory and cone testing. The performance of the probe turns out to be excellent in terms of data quality and testing convenience.

• Journal of the Korean Geotechnical Society
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• v.30 no.1
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• pp.17-25
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• 2014

Offshore wind turbine foundations are subjected to wind, current and wave loadings. Hence, both static and cyclic behaviors of foundation's soil are important for the design of offshore wind turbine foundation. Undrained cyclic behaviors of soils depend upon the number of loading cycles, vertical effective stress, cyclic shear strain, relative density, and the combination of cyclic and average shear stresses. In order to evaluate the effect of average and cyclic shear stresses on the undrained cyclic behavior of marine silty sand, cyclic direct simple shear (CDSS) tests are performed with relative density of 85%, vertical effective stress of 200 and 300 kPa, and failure criteria of either 15% double amplitude cyclic shear strain (${\gamma}_{cyc}$) or permanent shear strain (${\gamma}_{p}$). The results are presented in the form of design graphs or contour diagrams. The undrained cyclic behavior of marine silty sand is found to be dependent on cyclic and average shear stresses and/or the combination of both shear stresses. It is found that when significant average shear stress exists the permanent or progressive shear strain is the govering failure criteria instead of cyclic shear strain.

• Journal of the Korea Concrete Institute
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• v.16 no.4 s.82
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• pp.529-539
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• 2004

The corrosion of steel rebars has been the major cause of reinforced concrete deterioration. FRP(Fiber-reinforced polymer) rebar has emerged as one of the most promising and affordable solutions to the corrosion problems of steel reinforcement in structural concrete. However, FRP rebar is prone to deteriorate due to other degradation mechanisms than those for steel. The high alkalinity of concrete, for instance, is a possible degradation source. Therefore, the USA, Japan, Canada, UK. etc are using environmental reduction factor. Although difference design guidelines were drawn in many, including USA, Japan, Canada, UK etc, recommendations and coefficients that could take into account the long-term behavior of FRP reinforcement were not well defined. This study focuses on recommendation of environmental reduction factor of FRP rebar. Environment reduction factor were decided using durability test result. FRP rebars were subjected to twelve type of exposure conditions including alkaline solution, acid solution, salt solution and deionized water etc. The water absorption behavior was observed by means of simple gravimetric measurements and durability properties were investigated by performing tensile, compressive and short beam tests. Based on the experimental result, environmental reduction factor of hybrid FRP rebar(A), and (C) and CFRP rebar was decided as 0.85. Also, hybrid FRP rebar(B) and GFRP rebar were decided as 0.7 for the environmental reduction factor