• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.04a
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• pp.319-326
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• 2000

The purpose of this study is to evaluate seismic performance of reinforced concrete pier columns in Seohae Ground Bridge. Since the bridge was designed before preparing the seismic design specification the bridge columns of hollow hexagonal section were designed and constructed with insufficient seismic reinforcement details such as longitudinal and transverse reinforcement lap-splices. In order to take the necessary measures to improve its seismic performance experimental study was performed by small-scale test for the bridge columns, From the quasi-static test for small-scale column specimens the lap-splices were not critical for overall behavior of the column if sufficient lap-splice-length was provided. The test results of failure mode effective stiffness ductility and equivalent viscous damping ratio are presented.

• International Journal of Safety
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• v.3 no.1
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• pp.15-19
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• 2004

A new tower internal, which is called CSE, is presented. The CSE is composed of a nozzle perforated in its bottom along the entire periphery and equipped with a multi vane axial swirler at the inlet and hollow cylindrical separator at the outlet of the nozzle. According to the experimental work for obtaining the necessary hydraulic information of the CSE, which is used for preliminary design of a separation column, the CSE showed a stable operation over the wide rage of gas/liquid ratio. However, it caused large pressure drop due to the high gas velocity which should carry liquid droplets through the element. The high pressure drop may cause problems in energy recovery and the application of the CSE can be limited to the high pressure columns. Assuming that the tray efficiency of the CSE is the same with the existing separation columns, the results of the column design showed the size reduction of the column diameters by 30 to $40\%$ and investment cost saving, depending on operating conditions. The application of the CSE to separation column may also contribute to the de-bottlenecking the existing column.

• Steel and Composite Structures
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• v.9 no.1
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• pp.19-38
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• 2009

The present paper provides test data to evaluate the seismic performance of recycled aggregate concrete (RAC) filled steel square hollow section (SHS) beam-columns. Fifteen specimens, including 12 RAC filled steel tubular (RACFST) columns and 3 reference conventional concrete filled steel tubular (CFST) columns, were tested under reversed cyclic flexural loading while subjected to constant axially compressive load. The test parameters include: (1) axial load level (n), from 0.05 to 0.47; and (2) recycled coarse aggregate replacement ratio (r), from 0 to 50%. It was found that, generally, the seismic performance of RACFST columns was similar to that of the reference conventional CFST columns, and RACFST columns exhibited high levels of bearing capacity and ductility. Comparisons are made with predicted RACFST beam-column bearing capacities and flexural stiffness using current design codes. A theoretical model for conventional CFST beam-columns is employed in this paper for square RACFST beam-columns. The predicted load versus deformation hysteretic curves are found to exhibit satisfactory agreement with test results.

• Steel and Composite Structures
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• v.4 no.1
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• pp.37-48
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• 2004

This paper deals with the strength and deformation of both short and slender concrete filled steel tubular columns under the combined actions of axial compression and bending moment. Sixteen specimens were tested to investigate the effect of fiber reinforced concrete on the ultimate strength and behavior of the composite column. The primary test parameters were load eccentricity and column slenderness. Companion tests were also undertaken on eight numbers of similar empty steel tubes to highlight the synergistic effects of composite column. The test results demonstrate the influence of fiber reinforced concrete on the strength and behavior of concrete filled steel tubular columns.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.329-332
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• 2006

$Conform^{TM}$, a continuous extrusion forming process can produce a variety of very long extruded products such as aluminum alloyed wires, strips and profiles, hollow sectioned tubes, coated wires used in the current forming industry. This process has some advantages like as superiority of pre-heating free, availability of high extrusion ratio and continuous forming without stroke limit. But it is still difficult to analyze the realistic model of the process. In this study the analysis using two-dimensional model of $Conform^{TM}$ process together with several parametric investigations on the heat transfer are carried out by FEA code DEFORM $^{TM}2D$. In spite of simple model the results of analysis shows a good guidance to design the real process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.217-222
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• 1994

This paper describes the determination of optimal initial billet size for axisymmetric cold forging products using neural networks. The determination of optimal initial billet size is very important in forging design and forming sequence design, because the result of such designs and forming load can be different by variable initial billet sizes. The forming difficulty has been defined as the degree of difficulty in forming by 3 process ' forward extrusion, backward extrusion and upsetting. By neural networks a forming difficulty can be determined with the ratio of shape and forming process. From the graph of maximum, minimum, and average forming difficulties by variable billet sizes, the optimal billet size can be determined. The initial billets of a solid part and a hollow part whichwas determined by this study are compared with the sequence drawing generated by the one of forming sequence design system.

• Membrane Journal
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• v.14 no.1
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• pp.1-17
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• 2004

Dehumidification systems have been developed for the various applications, especially for the production of dry compressed air. Compressed air producing system attach $\varepsilon$ d with dehumidification unit have advantages such as high reliability, low error ratio, comfortable working conditions, etc. Conventional dehumidification systems have several economical drawbacks like high electric cost, high cost of adsorbent and it is not environmentally friendly system because freezing agent like a Freon has been used. Membrane dryer is emerging system which have economical advantages and environmental merits.

• Structural Engineering and Mechanics
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• v.74 no.1
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• pp.121-128
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• 2020

This paper presents an experimental study on the dynamic characteristics of infilled reinforced concrete (RC) frames. A 1/3-scaled, one-bay, three-storey RC frame was produced and tested by using operational modal analysis (OMA). The experiments were performed on five specimens: one reference frame with no infill walls and four frames with infill walls. The RC frame systems included infill walls made of hollow clay brick, which were constructed in four different patterns. The dynamic characteristics of the patterns, including the frequency, mode shapes and damping ratios in the in-plane direction, were obtained by 6 accelerometers. Twenty-minute records under ambient vibration were collected for each model, and the dynamic characteristics were determined using the ambient vibration testing and modal identification software (ARTeMIS). The experimental studies showed that the infill walls significantly affected the frequency value, rigidity and damping ratio of the RC frame system.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.49-52
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• 2006

Unlike columns having lap-spliced longitudinal bars in plastic hinge regions columns having 50% of lap-spliced bars were reported to have good ductilities relatively. But the effect of transverse reinforcements to deformability is not clearly confirmed. In this study scale models with different confinements were tested under various loading conditions. It was confirmed that deformability was increased with increase of transverse reinforcement ratio regardless of loading conditions and 75% of confinement yielded the satisfactory deformability.

• Journal of Power System Engineering
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• v.15 no.5
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• pp.61-66
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• 2011

Recently, the speed reducer which is applied to robot has conducted a steady development on developments in the field of robotics. Among them, Harmonic drive is a high-stiffness, precision-controlled speed reducer and has high precision, compact, light in weight and high-reduction-ratio characteristics. The feature of flexspline of Harmonic Drive are two types. One is Cup type, the other is Silk Hat type. Silk Hat type is used in case of lighter and more compact in spatial because Silk Hat Type is hollow. According to the shape of silk hat, diaphragm is fractured because stress is concentrated. In this paper, the various shapes of silk hat are suggested to improve the durability of silk hat. And in the case of each shape, a study on stress and deformation using the FEM tool was carried out on flexspline.