• Journal of Korean Society of Steel Construction
• /
• v.12 no.6
• /
• pp.727-736
• /
• 2000

The present study investigates the influences of vehicle induced loads on the thermal buckling behavior of straight and curved continuous welded rail (CWR) tracks. Quasi-static loads model is assumed to determine the uplift region, which occurs due to the vertical track deflection induced by wheel loads of vehicle. The lateral loads of vehicle induced by weight, the speed, the superelevation and curvature of track, and other dynamic vehicle track interaction, are included in the ratio of lateral to vertical vehicle load. Parametric numerical analyses are perfomed to calculate the upper and lower critical buckling temperatures of CWR tracks, and the comparison between the results of this work and the previous results without vehicle is also included.

• Journal of Korean Society of Steel Construction
• /
• v.17 no.6 s.79
• /
• pp.681-688
• /
• 2005

This study investigates an existing steel plate girder railroad bridge after superstructure rehabilitation to monitor static and dynamic responses using Fiber Bragg Grating (FBG) sensors. This paper also presents an experimental technique to estimate the vertical deflection of the bridge using FBG sensors. Seven FBG sensors are multiplexed in a single optical fiber and installed in parallel pairs along the length of the bridge, with one set at the top flange and the other at the bottom flange. In addition to FBG sensors, a conventional electric strain gauge and anLVDT are installed at the mid-span of the bridge for comparison. A test train consisting of one locomotive is placed at the center of the bridge to produce the maximum static effect. The train is also made to pass over the bridge at different speeds ranging from 10 km/h to 90 km/h to monitor the dynamic response of the bridge. This study demonstrates that the measured strains using the FBG sensor compared well with the readings from the electric strain gauge. The results show that the proposed instrumentation technique is capable of estimating the vertical deflection of the bridge for various loading conditions, which is crucial in structural health monitoring. Several dynamic characteristics of the bridge were also identified.

• Economic and Environmental Geology
• /
• v.54 no.1
• /
• pp.91-103
• /
• 2021

In order to estimate the vertical and horizontal structural in the Yangsan fault core line (Naengsuri area, Pohang), we carried out gravity field measurements and interpretation procedures such as Euler deconvolution method and curvature analysis in addition to the forward modelling technique (i.e. IGMAS+). We found a prominent gravity difference of more than 1.5 mGal across the fault core. This indicates a distinct density difference between the western and eastern crustal area across the Yangsan fault line. Comparing this gravity field interpretation with other existent geologic and geophysical survey data (e.g. LiDAR, trenching, electric resistivity measurements), It is concluded that (1) the prominent gravity difference is caused by the density difference of about 0.1 g/㎤ between the Bulguksa Granite in the west and the Cretaceous Sandstone in the east side, (2) the fault core is elongated vertically into a depth of about 2,000 meters and extended horizontally 3,000 meters to the NNE direction from Naengsuri area. Our results present that the gravity field method is a very effective tool to estimate a three -dimensional image of the active fault core.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.7
• /
• pp.54-62
• /
• 2016

The most efficient system for converting heat to electricity, AMTEC (Alkali Metal Thermal-to-Electric Convertor), is a device that directly converts heat energy to electricity using an alkali metal (sodium) as the working fluid. The AMTEC consists of a low pressure chamber, high pressure chamber, BASE (Beta-Alumina Solid Electrolyte), and artery wick. The main heat loss of the AMTEC system occurs in the low pressure chamber. A high power generation rate is thought to be obtainable by using a high temperature in the BASE. Therefore, to reduce the radiation heat loss, 6 types of radiation shields were examined to reduce the radiative heat loss in the low pressure chamber. The power generation rate of the AMTEC varied depending on the shape of the radiation shield. CFD (Computational Fluid Dynamics) analyses were carried out to optimize the shape of the radiation shield. As a result, the optimum radiation shield was found to consist of a curvature formed at the vertical point, in which case the dimensionless temperature (condenser temperature/BASE temperature) is approximately 0.665 and the maximum power generated is calculated to be 17.69W. Increasing the distance beween the BASE and condenser leads to an increase in the power generated, and the power generated with the longest distance was 17.58 W. The shields with multiple holes and multiple horizontal layers showed power reduction rates of 0.91 W and 2.06 W, respectively.

• Journal of Korean Society of Steel Construction
• /
• v.22 no.4
• /
• pp.313-324
• /
• 2010

In this study, an unbraced five-story steel-framed structure was designed in accordance with KBC2005 to understand the features of structural behavior for the arrangement of semi-rigid connections. An inelastic time history analysis of structural models was performed, wherein all the connections were idealized as fully rigid and semi-rigid. Additionally, horizontal and vertical arrangements of semi-rigid connections were used for the models. A fiber model was utilized for the moment-curvature relationship of a steel beam and a column, a three-parameter power model for the moment-rotation angle of the semi-rigid connection, and a three-parameter model for the hysteretic behavior of a steel beam, column, and connection. The base-shear force, top displacement, story drift, required ductility for the connection, maximum bending moment of the column, beam, and connection, and distribution of the plastic hinge were investigated using four earthquake excitations with peak ground acceleration for a mean return period of 2,400 years and for the maximum base-shear force in the pushover analysis of a 5% story drift. The maximum base-shear force and story drift decreased with the outer vertical distribution of the semi-rigid connection, and the required ductility for the connection decreased with the higher horizontal distribution of the semi-rigid connection. The location of the maximum story drift differed in the pushover analysis and the time history analysis, and the magnitude was overestimated in the pushover analysis. The outer vertical distribution of the semi-rigid connection was recommended for the base-shear force, story drift, and required ductility for the connection.

• Journal of the Korean GEO-environmental Society
• /
• v.16 no.9
• /
• pp.43-51
• /
• 2015

In this paper, a 3D shell-spring model that can perform time history analysis of buried pipelines is used to evaluate the effect of the incident direction of the earthquake motion. When applying harmonic motions, it is shown that the period of vibration has pronounced influence on the response of buried pipelines. With decrease in the period, the curvature of the pipeline and corresponding response are shown to increase. To evaluate the effect of the incident angle, the motions are applied in the direction of the pipleline, horizontal, and vertical planes. When the motion is applied parallel to the direction of the pipeline, it only induces bending strains and therefore, the response is the lowest. Under motions subjected in horizontal and vertical planes at an angle of $45^{\circ}$ from the longitudinal axis of the buried pipeline, the axial deformation is shown to contribute greatly to the response of the pipelines. When imposing two-components simultaneously, the calculated response is similar to the case where only single-component is imposed. It is because one component only induces bending strain, resulting in very small increase in the response. The trend of the response is shown to be quite similar for recorded motions. Therefore, it is concluded that use of a single-component is sufficient for estimation of the longitudinal response of buried pipelines.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.19 no.4 s.74
• /
• pp.375-387
• /
• 2006

Different from the previous studies which investigated seismic P-$\Delta$ effect in slender columns though comparison of response spectra according to stability coefficients obtained from the analyses based on the assumed moment-curvature relationship, the axial force and P-$\Delta$ effect in RC columns are investigated on the basis of the layered section method which can effectively consider the changes of stiffness and yield strength due to the application of axial force in RC members. Practical ranges of slenderness and stability coefficient are assumed, and sixty sets of horizontal/vertical earthquake inputs are used in the analysis. From the parametric study, it is noted that the maximum deformation of the slender RC column is hardly affected by P-$\Delta$ effect or vortical earthquake but dominantly affected by the applied axial force. Therefore, it can be concluded that no additional consideration for the P-$\Delta$ effect and vortical earthquake is required in the seismic design of a slender RC column if the axial force effect is taken into account in the analysis and design procedures.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2009.10a
• /
• pp.941-944
• /
• 2009

In this paper, we present a improved algorithm for thinning vein pattern. The vein image scanned using near infra-red is sliced in the horizontality or verticality direction, and then average value is gained from each slice image. Using curvature value changed from average value, search candidate part and extract vein pattern through re-searched candidate part in overlapping area. For the extracted vein pattern connecting, we proposed a DAL method that verify distance, angle and luminosity on pattern before tracking pattern extracted. The proposed improved thinning method is helpful for accurate connecting of vein pattern more than method used distance material in candidate part.

• Journal of The Korean Ophthalmological Society
• /
• v.59 no.11
• /
• pp.1049-1055
• /
• 2018

Purpose: To investigate the factors associated with glaucoma in patients with pseudoexfoliation syndrome by comparing features of the anterior segments and ocular biometry according to the presence or absence of open-angle glaucoma in pseudoexfoliation syndrome. Methods: We analyzed 96 patients (115 eyes) diagnosed as having pseudoexfoliation syndrome in this study. The patients were divided into two groups of simple pseudoexfoliation syndrome (64 patients, 76 eyes) and pseudoexfoliation glaucoma (32 patients, 39 eyes). We compared the age, sex, underlying disease, location of pseudoexfoliative material, iris change, degree of nuclear cataract, pupil dilatation, corneal endothelial cell counts, central corneal thickness, anterior chamber depth, axial length, corneal curvature, and intraocular pressure (IOP). Results: There were no significant differences between the two groups in terms of age (p = 0.694), sex (p = 0.161), diabetes (p = 0.440), hypertension (p = 0.238), pseudoexfoliative material observed in anterior capsule (p = 0.700), pupillary margin (p = 0.210), iris depigmentation (p = 0.526), pupillary ruff loss (p = 0.708), degree of nuclear cataract (p = 0.617), pupil dilatation (p = 0.526), central corneal thickness (p = 0.097), anterior chamber depth (p = 0.283), axial length (p = 0.095), or horizontal and vertical corneal curvature (p = 0.066 and 0.306, respectively). In pseudoexfoliation glaucoma, significantly higher IOP (p = 0.026), a high frequency of membrane formation (p = 0.047), and decreased corneal endothelial cell counts (p = 0.048) were observed. Conclusions: Pseudoexfoliation syndrome with open-angle glaucoma was shown to be associated with high IOP, decreased corneal endothelial cell counts, and a high frequency of membrane formation. Therefore, when such changes are observed in pseudoexfoliation syndrome patients, a higher risk of open-angle glaucoma should be recognized, and careful attentionis required accordingly.

• Journal of Korean Society of Steel Construction
• /
• v.22 no.4
• /
• pp.325-334
• /
• 2010

In this study, an unbraced five-story steel-framed structure was designed in accordance with KBC2005 to understand the features of structural behavior for the arrangement of semi-rigid connections. A pushover analysis of the structural models was performed, wherein all the connections were idealized as fully rigid and semi-rigid. Additionally, horizontal and vertical arrangements of the semi-rigid connection were adopted for the models. A fiber model was utilized for the moment-curvature relationship of the steel beam and the column, and a three-parameter power model was adopted for the moment-rotation angle of the semi-rigid connection. The top displacement, base-shear force, required ductility for the connection, sequence of the plastic hinge, and design factors such as the overstrength factor, ductility factor, and response modification coefficient were investigated using the pushover analysis of a 2D structure subjected to the equivalent static lateral force of KBC2005. The partial arrangement of the semi-rigid connection was found to have secured higher strength and lateral stiffness than that of the A-Semi frame, and greater ductility than the A-Rigid frame. The TSD connection was found suitable for use for economy and safety in the sample structure.