• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.5
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• pp.13-21
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• 2012

In this study, the response modification factor for a RC IMRF is evaluated via pushover analysis, where 5-story structures were designed in accordance with KBC2009. The bending moment-curvature relationship for beams and columns was identified with a fiber model, and the bending moment-rotation relationship for beam-column joints was calculated using a simple and unified joint shear behavior model and the moment equilibrium relationship for the joint. The results of the pushover analysis showed that the strength of the structure was overestimated with negligence of the inelastic shear behavior of the beam-column joint, and that the average response modification factor for category C was 7.78 and the factor for category D was 3.64.

• Journal of Korean Ophthalmic Optics Society
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• v.15 no.2
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• pp.195-199
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• 2010

Purpose: This study was to investigate the relevance between refractive and anatomical changes temporarily on the eyes after alcohol ingestion. Methods: Eight subjects (16 eyes) which were $24.5{\pm}1.5$ aged males drunk the alcohol of 0.42 g per kg of body weight within 30 minutes. Refractive errors, the radius of corneal curvature, corneal thickness, pupillary size, intraocular pressure, and the length of the ocular axis at 1 h, 4 h, and 24 h after alcohol ingestion were compared with them of non-alcoholic state. Results: At 1 h after alcohol ingestion, breath alcohol concentration was the highest (p<0.001), more negative spherical power was needed (p<0.05) for correction, pupillary diameter was decreased (p<0.05), intraocular pressure was decreased (p<0.001), and the length of the ocular axis was increased compared with each one of non-alcoholic state. At 4 h after alcohol ingestion, all anatomical changes were the same tendency as at 1 h after alcohol ingestion. But at 24 h after alcohol ingestion, both refractive changes and anatomical changes were not significant compared with them of non-alcoholic state. Conclusions: Temporary changes of refractive error after alcohol ingestion may be related with decrease of intraocular pressure and increase of the length of ocular axis.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.3
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• pp.397-402
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• 2014

Purpose: To investigate the relationship between axial length (AL) and anthropometric parameters in Korean children. Methods: This study included 40 urban school children aged 11-12 years (mean age, $11.95{\pm}0.22$ years; 45.0% girls) residing in Seoul, South Korea. AL (using partial coherence laser interferometry), corneal radius, refractive error, height (m), and weight (kg) were measured. Body mass index (BMI $[kg/m^2]=weight/[height]^2$) and degree of obesity (DO[%]=[actual weight standard weight]/standard weight) were calculated. Furthermore, the number of hours spent reading, watching television, and using a computer every day was determined using a detailed questionnaire. Results: The students had a mean spherical equivalent refraction of $1.06{\pm}0.84$ D. Weight (r=0.427, p=0.006), BMI (r=0.508, p=0.001), and DO (r=0.371, p=0.018) showed a significant positive correlation with AL. Furthermore, longer AL was significantly associated with heavier weight (p=0.041), and higher BMI (p=0.015), and higher DO quartiles (p=0.042). After adjust for age, sex, and near-work activities, multivariate linear regression models showed that weight, BMI, and DO were still significantly associated with AL. Among the near-work activities, daily reading time was significantly associated with AL. Conclusions: AL was positively related to weight as well as daily reading time in Korean urban school children.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.1
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• pp.105-115
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• 2009

Numerical analysis of shear walls governed by flexural behavior is conducted for the seismic control performance of proposed friction dampers installed at the center of coupling beams. Control effectiveness of shear walls connected by beams with the proposed dampers are compared for single shear wall with same flexural rigidity. Average responses of the shear walls with the dampers are found with seven scaled-downed earthquakes based on KEC 2005 design spectrum. Slip load is the most important design parameter. It is designed to be 5, 10, 20, 30, 60, 90% of total vertical shear force at damper location to prevent damper slip in specific stories. Nonlinear time-history analysis is conducted by using SeismoStruct analysis program. Seismic control performance of the dampers is evaluated for base shear, energy dissipation, curvature and top-floor displacement. Results show that the dampers are the most effective in reducing the responses when their total slip load is 30% of total vertical shear force.

• Journal of the Korean Institute of Gas
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• v.1 no.1
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• pp.21-26
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• 1997

This paper presents the numerical results of six corrugation models which compute the stress behaviours and stress levels of the membrane structure under the hydrostatic pressure of cryogenic liquids and thermal loadings using a non -linear finite element analysis program. A three-dimensional analysis of various corrugation geometries was performed on the maximum mean normal stress distributions along the upper surface of the membrane sheet. Comparisons of the FEM results for various geometry models of the corrugation are presented, which shows that the corrugated configuration of the ring knot model can be effectively performed for the combined forces such as the hydrostatic pressure and thermal loading in comparison with the Technigaz type corrugation which has small comer and apex curvatures. The FEM results show that the ring knot corrugation can be used for the deepest depth, 180m of the LNG storage tank in comparison with other corrugation models.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.9
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• pp.859-869
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• 2009

The sharp indenters such as Berkovich and conical indenters have a geometrical self-similarity in theory, but different materials have the same load-depth curve in case of single indentation. In this study, we analyze the load-depth curves of conical indenter with angles of indenter via finite element method. From FE analyses of dual-conical indentation test, we investigate the relationships between indentation parameters and load-deflection curves. With numerical regressions of obtained data, we finally propose indentation formulae for material properties evaluation. The proposed approach provides stress-strain curve and the values of elastic modulus, yield strength and strain-hardening exponent with an average error of less than 2%. It is also discussed that the method is valid for any elastically deforming indenters made of tungsten carbide and diamond for instance. The proposed indentation approach provides a substantial enhancement in accuracy compared with the prior methods.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.7
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• pp.757-764
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• 2014

In this study, the effect of shape parameters on the J-R curves of curved CT specimens was evaluated using the limit load method. Fracture toughness tests considering the shape factors L/W and $R_m/t$ of the specimens were also performed. Thereafter, the J-R curves of the curved CT specimens were compared using the J-integral equation proposed in the ASTM (American Society for Testing and Materials) and limit load solution. The J-R curves of the curved CT specimens were also compared with those of the CWP (curved wide plate), which is regarded to be similar to real pipe and standard specimens. Finally, the effectiveness of the J-R curve of each curved CT specimen was evaluated. The results of this study can be used for assessing the applicability of curved CT specimens in the accurate evaluation of the fracture toughness of real pipes.

• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.4
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• pp.333-338
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• 2008

The coastal zone is a delicate and dynamic area in which the majority of a water kinetic energy is dissipated. These processes are subsequent to the transport of the beach materials. In comparison to emerged breakwaters, submerged structures permit the passage of some wave energy and in turn allow for circulation along the shoreline zone. This research aims to examine the beach erosion prevention capability of submerged structure by laboratory model. The flow characteristics behind a submerged obstacle with bottom gap were experimentally investigated at Re = $1.2{\times}10^4$ using the two-frame PIV(CACTUS 2000) system. Streamline curvature field behind the obstacle has been obtained by using the data of time-averaged mean velocity information. And the large eddy structure in the separated shear layer seems to have signification influence on the development of the separated shear layer. As bottom gap size increases, the recirculation occurring behind the obstacle moves toward downstream and its strength is weakened.

• Tunnel and Underground Space
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• v.24 no.3
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• pp.212-223
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• 2014

In this study, the stability analyses for metal mine roadways at a great depth were performed. In-situ stress measurements using hydrofracturing, numerous laboratory tests for rock cores and GSI & RMR classifications were conducted in order to find the physical properties of both intact rock and in-situ rock mass distributed in the studied metal mine. Through the scenario analysis and probabilistic assessment on the results of rock mass classification, the in-situ ground conditions of mine roadways were divided into the best, the average and the worst cases, respectively. The roadway stabilities corresponding to the respective conditions were assessed by way of the elasto-plastic analysis. In addition, the appropriate roadway shapes and the support patterns were examined through the numerical analyses considering the blast damaged zone around roadway. It was finally shown to be necessary to reduce the radius of roadway roof curvature and/or to install the crown reinforcement in order to enhance the stability of studied mine roadways.

• Journal of the Korea Concrete Institute
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• v.14 no.6
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• pp.900-909
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• 2002

Fibers play a role to increase the tensile strength and cracking resistance of concrete structures. The post cracking behavior must be clarified to predict cracking resistance of fiber reinforced concrete. The purpose of this study is to develop a realistic analysis method for the post cracking behavior of synthetic fiber reinforced concrete members. For this purpose, the cracked section is assumed to behave as a rigid body and the pullout behavior of single fiber is employed. A probabilistic approach is used to calculate effective number of fibers across crack faces. The existing theory is compared with test data and shows good agreement. The proposed theory can be efficiently used to describe the load-deflection behavior, moment-curvature relation, load-crack width relation of synthetic fiber reinforced concrete beams.