• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.12
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• pp.1131-1138
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• 2007

This paper studies experimentally on the building-up process for the amplitude of a commercial truck vibration induced by brake judder. A front axle drum equipped with a drum brake system is utilized for this experiment. A brake dynamo test, a real vehicle ride test and a real vehicle braking test are performed for the analysis of brake judder. The brake dynamo test measures judder by applying brake chamber pressures of 1, 2 and 3 bar at initial brake pad temperatures of $100^{\circ}C$ and $150^{\circ}C$. In order to assess the vertical acceleration at the front axle, the real vehicle ride test on a straight test road with velocities of 20, 40, 60 and 80 km/h is performed. The real vehicle braking test is carried out at the deceleration rate of 0.2g from a velocity of 90km/h for evaluating the vertical, lateral and longitudinal accelerations both at the front axle and at the cab floor under the driver's seat. The magnitudes and frequencies of the measured peak accelerations from the brake dynamo test, the real vehicle ride test and the real vehicle braking test are comparatively analyzed. This paper shows that the vibration produced by brake judder is built up due to the brake system's peak acceleration frequency being close to the vehicle ride mode's frequency.

• Journal of the Korea Concrete Institute
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• v.23 no.5
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• pp.569-579
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• 2011

Reinforced concrete walls subjected to cyclic loading show complicated inelastic behaviors varying with aspect ratio, re-bar detail, and loading condition. In the present study, a macro model for nonlinear analysis of reinforced concrete walls was developed. For exact prediction of inelastic flexure-compression and shear behaviors, the macro model of the wall was idealized with longitudinal and diagonal uniaxial elements. The uniaxial elements consist of concrete and re-bars. Simplified cyclic models for concrete and re-bars under uniaxial loading was used. For verification, the proposed model was applied to slender, lowrise, and coupled walls subjected to cyclic loading. The results showed that the proposed method predicted the nonlinear behaviors of the walls with reasonable precision.

• Parasites, Hosts and Diseases
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• v.23 no.1
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• pp.111-122
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• 1985

The present study was performed to observe the ultrastructure of the integument of adult Paragonimus westermani. Dogs experimentally infected with 60 metacercariae of F. westermani were autopsied 4 months after the infection. Adult p. westermani were extracted from the dogs and the fine structure was studied by means of scanning and transmission electron microscope. The findings are as follows: 1. Scanning electron microscopic findings showed that the spines and the papillae are distributed at whole body surface but the well developed spines or papaillae are shown around the oral sucker and ventral sucker. 2. At the end of the body, excretory pore was found, the shape was irregular. 3. Transmission electron microscopic findings showed that plasma membrane, tegument, basal lamina, connective tissue, circular muscle layer, longitudinal muscle layer. nerve axon and tegumental cell were observed. 4. In higher magnification, plasma membrance and bar-shaped granules were found at the outer surface of the tegument.

• Journal of Korean Society of Steel Construction
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• v.25 no.6
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• pp.635-647
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• 2013

PSRC composite column is a concrete encased steel angle column. In the PSRC composite column, the steel angles placed at the corner of the cross-section resists bending moment and compression load. In the present study, using the performance criteria in KBC 2009, cyclic lateral loading test was performed for PSRC columns to verify the seismic performance. The test parameters were the column type, the use of continuous hoop, and the use of studs for steel angle. 2/3 scale specimens of a conventional composite column and three PSRC columns were tested. The test results showed that the load-carrying capacity predicted by KBC 2009 correlated well with the test results. The specimens also exhibited good deformation and energy dissipation capacities. After concrete cover spalling under cyclic loading, the load-carrying capacity were decreased by buckling of longitudinal bars and steel angles. When continuous hoop was used, the deformability of the PSRC column was improved, preventing early buckling of the steel angles.

• Journal of the Earthquake Engineering Society of Korea
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• v.9 no.3 s.43
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• pp.77-85
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• 2005

After the collapse of the World Trade Center in september 11, 2001 and due to the frequent fire-caused damages of buildings during earthquake attacks, social concerns have been increased for the fire proof of the structural members of buildings. Recently, researches have been conducted to improve the fire resistance for building members not by the traditional ways but by utilizing the fire-resisting characteristics of reinforced concrete and structural characteristics of H-steel. In this paper, laboratory tests were conducted in room temperature to investigate the structural performance of the composite beams, which were developed to improve the fire resistance, comprising with concrete incasement between upper and lower flanges of H steel. From the experimental results, the displacement ductility factors of $6\~8$ were obtained. The difference of flexural behavior ol H steel-partial concrete incased composite beams with various composite details seems to be minor. The amount of longitudinal rebars is the most influential factor for the flexural strength of the composite beams. Therefore, if this type of composite beams are selected for designing a building located in moderate seismic lone, identical beam size could be used in several stories of the building.

• Transactions of Materials Processing
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• v.25 no.1
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• pp.12-20
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• 2016

Press machines and dies are commonly used for 3D curved sheet forming. Using conventional die forming can cause economic problems since various modifications of the die shape are required depending on the product shape. Various types of flexible forming such as multi-point dieless forming (MDF), flexible incremental roll forming have been developed to improve the needed process flexibility. Although MDF can reduce the production cost using reconfigurable dies, it still has significant material loss. Drawbacks such as wrinkling, dimpling, and forming errors can also occur despite continuous investigations to mitigate these defects. A novel sheet forming process for 3D curved surfaces, a flexibly-reconfigurable roll forming (FRRF), has been recently proposed to overcome the economic and technical limitations of current practice. FRRF has no limitation on blank size in the longitudinal direction, and also minimizes or eliminates forming defects such as wrinkling and dimpling. Feasibility studies of FRRF have been conducted using FE simulations for multi-curved shapes and various sheet thicknesses. Therefore, the fabrication of a FRRF apparatus is required for any follow-up studies. In the current study, experiments with reconfigurable rollers were conducted using a simple design pre-FRRF apparatus prior to fabricating the full size FRRF apparatus. There are three candidates for the reconfigurable roller: a bar-type shaft, a flexible shaft, a ground flexible shaft. Among these candidates, the suitable reconfigurable roller for FRRF is determined through various forming tests.

• Ecology and Resilient Infrastructure
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• v.6 no.4
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• pp.287-294
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• 2019

This study investigated longitudinal changes in riverbed materials properties and temporal alteration of river channel geomorphology in the Geum River basin, where two multipurpose dams(Yongdam Dam and Daecheong Dam) were built in upstream area. We carried out grain size distribution analyses and measured soil organic matter contents of riverbed materials taken at the upper and lower sites of the two large dams. We also estimated the channel width, bar area and vegetation encroachment using the oldest map and aerial photographs taken before and after the construction of the dams. The results can contribute to increasing understandings of dam induced habitat alteration in river ecosystem.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.3
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• pp.58-68
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• 2014

Transverse steel bars are used in the plastic hinge zone of columns to insure adequate confinement, prevention of longitudinal bar buckling and ductile behavior. Fabrication and placement of rectangular hoops and cross-ties in columns are difficult to construct and require larger amount of transverse steels. In this paper, to solve these problems, the new lateral confinement method using oblong hoop is proposed for the transverse confinement of columns of the oblong cross-section and flared column. The experimental study for octagonal oblong cross-section was carried out by the flared columns test in strong axis. The lateral confinement method using proposed oblong hoop detail showed satisfactory performance of lateral confinement. Therefore it can be the alternative for oblong cross-section and flared column with improved workability and cost-efficiency.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.6
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• pp.1-9
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• 2015

Transverse steel bars are used in the plastic hinge zone of columns to insure adequate confinement, prevention of longitudinal bar buckling and ductile behavior. Fabrication and placement of rectangular hoops and cross-ties in columns are difficult to construct. Details of reinforcement for rectangular section require a lot of rectangular hoops and cross-ties. In this paper, to solve these problems, the new lateral confinement method using oblong hoop is proposed for the transverse confinement of the flared column. It can be the alternative for oblong cross-section and flared column with improved workability and cost-efficiency. The final objectives of this study are to suggest appropriate oblong hoop details and to provide quantitative reference data and tendency for seismic performance or damage assessment based on the drift levels such as residual deformation, elastic strain energy. This paper describes factors of seismic performance such as ultimate displacement/drift ratio, displacement ductility, response modification factor, equivalent viscous damping ratio and effective stiffness.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.6
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• pp.72-81
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• 2014

This paper reports the test results of reinforced concrete exterior beam-column joints with high-strength concrete. The main parameters of eight specimens were joint failure modes, the compressive strength of concrete, and the head shapes of steel bars. All specimens were designed according to ACI 352R-02 design recommendations. Two types of failure modes were considered; J-failure and BJ-failure. The longitudinal steel bars were anchored by 90 degree standard hooks or headed reinforcement. Experimental results indicated that the current ACI design recommendation limited by the compressive strength of concrete somewhat underestimated the strength of beam-column joints with high-strength concrete. In the specimens showed joint shear failure, the strength of beam-column joints with headed bars was approximately 10 percent higher than that of joints with 90 degree standard hooks.