• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.4
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• pp.1290-1300
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• 1996

The finite element method, based on rigid-plastic formulation, is widely used to simulate metal forming processes. In order to improve the computational efficiency of the rigid-plastic FEM, one-point integration is used to evaluate the stiffness matrix with four-node rectangular elements and eight-node brick elements. In order to control the hourglass modes, hourglass strain rate components were introduced and included in the effective strain rate definition, Numerical tests have shown that the proposed one-point integration scheme reduces the stiffness matrix evaluation time without deteriorating the convergence behavior of Newton-Raphson method. Simulations of a ring compression, a plane-strain closed-die forging and the three-dimensional spike forging processes were carried out by using the proposed integration method. The simulation results are compared to those obtained by applying the conventional integraiton method in terms of the solution accuracy and computational efficiency.

• Journal of the Korea Concrete Institute
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• v.21 no.2
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• pp.169-178
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• 2009

An equation for calculating confining reinforcement amount of RC bridge columns, specified in the current bridge design codes, has been made to provide additional load-carrying strength for concentrically loaded columns. The additional load-carrying strength will be equal to or slightly greater than the resistant strength of a column against axial load, which is lost because the cover concrete spalls off. The equation considers concrete compressive strength, yield strength of transverse reinforcement, and the section area ratio as major variables. Among those variables, the section area ratio between the gross section and the core section, varying by cover thickness, is a variable which considers the strength in the compression-controlled region. Therefore, the cross section ratio does not have a large effect in the aspect of ductile behavior of the tension-controlled region, which is governed by bending moment rather than axial force. However, the equation of the design codes for calculating confining reinforcement amount does not directly consider ductile behavior, which is an important factor for the seismic behavior of bridge columns. Consequently, if the size of section is relatively small or if the section area ratio becomes excessively large due to the cover thickness increased for durability, too large an amount of confining reinforcement will be required possibly deteriorating the constructability and economy. Against this backdrop, in this study, comparison and analysis were performed to understand how the cover thickness influences the equation for calculating the amount of confining reinforcement. An equation for calculating the amount of confining reinforcement was also modified for reasonable seismic design and the safety. In addition, appropriateness of the modified equation was examined based on the results of various test results performed at home and abroad.

• International Journal of Concrete Structures and Materials
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• v.9 no.3
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• pp.345-367
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• 2015

Past earthquakes have signaled the increased collapse vulnerability of mainshock-damaged bridge piers and urgent need of repair interventions prior to subsequent cascading hazard events, such as aftershocks, triggered by the mainshock (MS). The overarching goal of this study is to quantify the collapse vulnerability of mainshock-damaged substandard RC bridge piers rehabilitated with different repair jackets (FRP, conventional thick steel and hybrid jacket) under aftershock (AS) attacks of various intensities. The efficacy of repair jackets on post-MS resilience of repaired bridges is quantified for a prototype two-span single-column bridge bent with lap-splice deficiency at column-footing interface. Extensive number of incremental dynamic time history analyses on numerical finite element bridge models with deteriorating properties under back-to-back MS-AS sequences were utilized to evaluate the efficacy of different repair jackets on the post-repair behavior of RC bridges subjected to AS attacks. Results indicate the dramatic impact of repair jacket application on post-MS resilience of damaged bridge piers-up to 45.5 % increase of structural collapse capacity-subjected to aftershocks of multiple intensities. Besides, the efficacy of repair jackets is found to be proportionate to the intensity of AS attacks. Moreover, the steel jacket exhibited to be the most vulnerable repair intervention compared to CFRP, irrespective of the seismic sequence (severe MS-severe or moderate AS) or earthquake type (near-fault or far-fault).

• Korean Institute of Interior Design Journal
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• v.22 no.5
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• pp.188-198
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• 2013

Advancement toward aging society has presented the importance of house planning in consideration of the elderly, increasing the necessity of such planning. Therefore the importance of indoor design guideline for elderly houses has been stressed and the understanding of the aging in regard to this trend will create more mature spaces. In line with this trend the purpose of this study is to study the medical factors related with bathroom interior design guidelines of the existing elderly houses from the viewpoint of deteriorating physical functions due to aging process. In order to research the deterioration of physical functions due to aging literatures of medical and exercise physiology were used and concerning the existing bathroom design guidelines for the aged people, the guideline items of behavior facilitation, physiological maintenance and perceptual maintenance aspects out of Murtha & Lee's user benefit criteria(1976) related with physical functions were selected to research in relation with the knowledge about the deterioration phenomena of physical functions. Physical aging and deterioration aspects were classified from the viewpoint of musculoskeletal disorder, cardiovascular disorder, respiratory disorder, gastronomy disorder, urology disorder, somatosensory disorder, endocrine disorder, immune disorder, nervous disorder and skin diseases and these were utilized in interpreting total 100 items of bathroom design guideline. Because bathroom is the space where many physical movements are done, it had the closest relationship with the deterioration of musculoskeletal health in general and as bathroom is the space where people use water and feel the difference in temperature and moisture more than other spaces, deterioration of skin and somatosensory health had the next closest relationship. The result of this study revealed that regarding the deterioration of physical functions of the elderly people in aspect of their perceptibility as designers will design creatively and sincerely based on its relationship with nervous system in future, the result of this study will be used to develop better spatial designs efficiently to meet for the aging society.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.1
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• pp.6-12
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• 2018

Recently, The use of the curtain wall method is increasing in construction. The curtain wall construction is widely applied to the exterior wall of the building for shortening construction period and economical efficiency. However, the replacement of deterioration of the weather resistance and structural behavior of the sealing material connecting the curtain wall method and the glass frame is necessary for introduction of the stable curtain wall method and quality improvement in accordance with KS F 4910 standard. In this study, the elastic restoring force test was performed in the external environment. In this study, the deterioration of the sealant was evaluated for structural sealants. In Korea, studies on the variable displacement behavior of structural sealants are lacked. In this study, the reproduced results in laboratory conditions are compared with the deteriorating conditions exposed to the external environment, and they are reflected in the design of sealing materials in the future. According to the results of the study, it was confirmed that the existing structure sealant meets the quality standard of KS F 4910, but in the conditions performed in this study, adhesion failure of the specimen and cracking of the surface occurred. Especially, in the weather resistance test, it is necessary to evaluate the long-term durability performance of the structural sealant used in the curtain wall method by checking the insoluble state of all the test pieces. Therefore, in order to apply a conventional structural sealant to the site, it is necessary to introduce another durability performance evaluation.

• Journal of Korean Society of Steel Construction
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• v.17 no.6 s.79
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• pp.673-679
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• 2005

According to continuous welded rails on a bridge, temperature changes bring about the expansion of the bridge deck,adding axial forces on the track. Moreover, the ballast on the bridge deck expansion joint is moved due to the bridge deck. The longer the bridge deck is, the greater the influence will be, loosening the ballast, causing track irregularities, and deteriorating passenger comfort. Considering the structure of the bridge itself and tolerance for track irregularities caused by the loosened ballast on the bridge, the maximum length of the deck should be less than 80 m, which is the same as the standard of French railways. In this study, the interaction between the expansion related to the bridge length and the irregularity in the longitudinal level, referring to measurements and maintenance work performed in high-speed railways, was analyzed. This research shows that the installation of a sliding plate or a vertical ballast stopper is not a good option, since it is difficult. On the other hand, the installation of a ZLR fastener or gluing is easy, but its influence is insignificant. In conclusion, switch tie tamping or manual tamping is more effective than other methods of what?

• Korean Journal of Social Welfare
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• v.61 no.4
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• pp.5-33
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• 2009

This study attempted to evaluate the effectiveness of the Supportive Project for the Priority Region of Educational Welfare Investment(SPPREWI) which has been put into action in Korea as a part of national policies for poor school children. In so doing this study aimed to test SPPREWI's legitimacy as well as whether we have to continue this program or not. In order to fulfill this research purpose researchers identified several outcome indicators of SPPREWI, which represent psychosocial and cognitive adjustment. The variables pertaining to psychosocial adjustment domain are: self-concept; depression, anxiety, and suicidal impulse; inclination of assault and indignation; delinquency; school life adjustment; and change in social relations. The variables of cognitive adjustment include recognition of self-control in learning; control strategy of learning behavior; and preparedness for job hunting. In this study the quasi-experimental group contained students from schools which are under the SPPREWI. The control group was composed of students from schools which were free from SPPREWI but under the influence of deteriorating school environment. The quasi-experimental group and the control group were compared in terms of outcome indicators presented earlier. Within the quasi-experimental group both the students below poverty-line and the students above poverty-line were divided into two groups each by the level of service use, and were compared in terms of the outcome variables presented earlier. Study results supported the argument that SPPREWI was effective generally in improving students' school adjustment. Study results also showed that the variable of 'school nurturance' played a significant role in moderating the effect of SPPREWI on a couple of outcome variables specially when schools' overall educational environment was in poor condition. Implication as well as suggestion were presented on the basis of study findings.

• Journal of the Korean Applied Science and Technology
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• v.37 no.5
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• pp.1441-1453
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• 2020

The purpose of this study was to compare acne recognition and management methods for those in their 20s and 30s who live in China and have acne. A total of 600 questionnaires were distributed and 533 copies were used for final analysis, excluding 27 of the 560 collected questionnaires. As a result of the study, the difference in perception of the cause of acne, management perception, and exacerbation factor of Chinese people according to age showed'management perception' t=3.380, and deteriorating factor recognition' t=2.314, indicating that there was a difference in perception of acne according to age. It was found that the recognition degree of acne is higher in the 20s than in the 30s. Through this study, by comparing and analyzing the perceptions and management methods of acne according to the age of Chinese people, the changes in acne management perception and behavior according to the change of the times were identified, and the difference between Korean and Chinese perceptions of acne, and later acne skin It is believed that it can be provided as a basic data for finding an effective management method.

• Journal of the Korea Concrete Institute
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• v.22 no.1
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• pp.19-27
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• 2010

Aging and severe environments are major causes of damage in reinforced concrete (RC) structures such as buildings and bridges. Deterioration such as concrete cracks, corrosion of steel, and deformation of structural members can significantly degrade the structural performance and safety. Therefore, effective and easy-to-use methods are desired for repairing and strengthening such concrete structures. Various methods for strengthening and rehabilitation of RC structures have been developed in the past several decades. Recently, FRP composite materials have emerged as a cost-effective alternative to the conventional materials for repairing, strengthening, and retrofitting deteriorating/deficient concrete structures, by externally bonding FRP laminates to concrete structural members. The main purpose of this study is to investigate the effectiveness of adaptive neuro-fuzzy inference system (ANFIS) in predicting behavior of circular type concrete column retrofitted with FRP. To construct training and testing dataset, experiment results for the specimens which have different retrofit profile are used. Retrofit ratio, strength of existing concrete, thickness, number of layer, stiffness, ultimate strength of fiber and size of specimens are selected as input parameters to predict strength, strain, and stiffness of post-yielding modulus. These proposed ANFIS models show reliable increased accuracy in predicting constitutive properties of concrete retrofitted by FRP, compared to the constitutive models suggested by other researchers.

• 한국노년학
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• v.32 no.4
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• pp.993-1011
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• 2012

The purpose of this study is to investigate the factors associated with the incidence and the transition of disability among Korean older adults. Samples consist of 1,454(42.7%) men and 2,032(58.3%) women aged 65 and over who participated in the 1st and 2nd wave of the Korea Longitudinal Study of Aging: KLOSA. To estimate the level of disability, ADL and IADL disability indexes are used. As the results, major risk factors for ADL/IADL disability incidence include injury, vision problem, cognitive function, depression, health behavior, socioeconomic characteristics and age. Among the normal older adults, the odds ratio of having dementia symptoms at 2nd wave(2008) are 2.0 times greater for the older adults who have less cognitive function than those who don't have at 1st wave(2006). Among the older adults with chronic diseases, the odds ratio of having disability at 2nd wave are 1.8 times greater for the older persons who have depression than those who don't have at 1st wave. Secondly, concerning the predictors affecting the disability transition among the disabled older adults at 1st wave, the likelihood of remaining at the same level or deteriorating the level of IADL disability, as compared with improving the level, is associated with having less instrumental support or being older. These results indicate that it is necessary to prefer multilevel intervention in order not only to prevent the incidence of disability, but also to prolong the deterioration of disability in the older adults.