• Steel and Composite Structures
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• v.33 no.3
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• pp.333-346
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• 2019

Foam ceramic materials contribute to the explosion effect weakening on concrete structures, due to the corresponding excellent energy absorption ability. The blast resistance of concrete members could be improved through steel-foam ceramics as protective cladding layers. An approach for the modeling of dynamic response of steel-foam ceramic protected reinforced concrete (Steel-FC-RC) slabs under blast loading was presented with the LS-DYNA software. The orthogonal analysis (five factors with five levels) under three degrees of blast loads was conducted. The influence rankings and trend laws were further analyzed. The dynamic displacement of the slab bottom was significantly reduced by increasing the thickness of steel plate, foam ceramic and RC slab, while the displacement decreased slightly as the steel yield strength and the compressive strength of concrete increased. However, the optimized efficiency of blast resistance decreases with factors increase to higher level. Moreover, an efficient design method was reported based on the orthogonal analysis.

• Earthquakes and Structures
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• v.26 no.6
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• pp.463-475
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• 2024

The study aims to investigate the pounding that occurs between the isolator's ring and slider of isolated structures resulting from excessive seismic excitation, while considering soil-structure interaction. The dynamic responses and poundings of structures subjected a series seismic records were comparatively analyzed for three different soil types and fixed-base structures. A series of parametric studies were conducted to thoroughly discuss the effects of the impact displacement ratio, the FPB friction coefficient ratio, and the radius ratio on the structural dynamic response when considering impact and SSI. It was found that the pounding is extremely brief, with an exceptionally large pounding force generated by impact, resulting in significant acceleration pulse. The acceleration and inter-story shear force of the structure experiencing pounding were greater than those without considering pounding. Sudden changes in the inter-story shear force between the first and second floors of the structure were also observed. The dynamic response of structures in soft ground was significantly lower than that of structures in other ground conditions under the same conditions, regardless of the earthquake wave exciting the structure. When the structure is influenced by pulse-type earthquake records, its dynamic response exhibits a trend of first intensifying and then weakening as the equivalent radius ratio and friction coefficient ratio increase. However, it increases with an increase in the pounding displacement ratio, equivalent radius ratio, friction coefficient ratio, and displacement ratio when the structures are subjected to non-pulse-type seismic record.

• Tunnel and Underground Space
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• v.19 no.5
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• pp.397-406
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• 2009

Recently, the number of industrial structures that must be demolished due to structural deterioration and unsatisfactory functional conditions has been increased. To minimize environmental hazardous factors created during the process of demolition, the explosive demolition method has been applied increasingly. This execution case was intended to describe an application of the explosive demolition method to the demolition of a Crusher & Screen structure, which was a large-section reinforced concrete special structure. It was deemed necessary due to its structural deterioration and unsatisfactory functional condition. Various pre-weakening processes and blasting patterns were applied to the large-section reinforced concrete members, and to reduce blasting vibration and impact vibration, time intervals were established for blasting in the same column and for blasting between blasting blocks. By applying the explosive demolition method to the demolition of a large-section reinforced concrete special structure, the explosive demolition was completed safely and efficiently, without causing any damage to surrounding facilities.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.5
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• pp.11-18
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• 2012

Deterioration and weakening is advanced in compliance with flowing of time and the change of environment in RC structures. Consequently, strength and serviceability decreases, finally, the life of infrastructure shortens and safety characteristics decreases. Accordingly, in this study, a new method to develop a strengthening method using the vacuum impregnation, which increases durability of the infrastructure occurred the safety reduction due to the performance degradation and increases the life of infrastructure by improving the durability compared to the existing method, was planned. For flexural tests, the maximum strength was a low-end order from high order as follows: (1) vacuum impregnation with 2 fold reinforcement, (2) fiber sheet 2 fold reinforcement, (3) vacuum impregnation with 1 fold reinforcement, (4) fiber sheet 1 fold reinforcement, and (5) nothing. Also, for confirmation results about durability, when the fiber reinforcement is being exposed to the inferior environment, the remaining tensile strength exceeded of 90% or more for all environments. This is because the reinforcement used in this research shows the excellent resistance in severe environment.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.4
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• pp.639-647
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• 2002

A simplified analytical procedure is presented to estimate the reduction of elastic lateral stiffness of steel moment frames arising from the radius-cut dogbone weakening. With the original radius-cut dogbone shape, it is almost impossible or too complicated to integrate analytically the mathematical expressions encountered when applying the conjugate beam method to compute the beam deflection component. In this study, the problem is circumvented by replacing the original radius-cut dogbone with an equivalent dogbone of constant width. The equivalence between the two is established by imposing an equal dogbone elongation criterion. This approach is justified by using a calibrated finite clement analysis. Then, the elastic lateral deflection components from the column, panel zone, and beam are derived for a typical beam-column subassembly. The derived results can be used to evaluate the reduction of the frame lateral stiffness. Case studies conducted within some practical ranges of frame configurations show that the reduction in frame lateral stiffness due to the presence of dogbone cut is on the order of 1 to 2 percent and is reasonably negligible in practical sense.

• Journal of the Korean Home Economics Association
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• v.30 no.1
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• pp.283-309
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• 1992

This study examines work and family life of married women employed in a manufacturing industry. Data were gathered from the use of fact-to-face interview method from a sample of 230 married working women. The major findings of this study can be summarized as follows : (1) With high rates of change of job, most of the respondents remain unstable in their working situation. It was shown that the important factors influencing job satisfaction of married women are women's life cycle, degree of contribution of wife's income toward total family income, and husband's attitude toward wife's empolyment. The degree of job satisfaction is also strongly influenced by labor structural factors such as pay, work environment and fringe benefits. (2) The amount of household labor time was limited by job-related factors rather than by family-related factors, because among these working women employment itself is necessarily for their subsistance. (3) It was shown that wives participated more actively in their marital communications than their husbands. Most of the respondents showed the syncratic type of the decision making patterns, but this results does not necessarily mean wives exercised an equal power with their husbands. The economic factors and the emotional instability of the husband are the ones mostly influencing marital conflicts of the employed women. It was found that the respondents easily revealed marital conflicts related to personal problems of their husbands(such as extramarital affairs, gambling and alchoholism). However, they tried to overcome the structural conflicts related to authoritarian attitudes of their husbands or economic problems without any complaints. (4) Mothers have difficulty in controlling their adolescent children, due to the weakening of parental authority. Although most of the respondents perceived their employment as having negative impacts on their children, they still have high expectations toward their children. Inspite of low degree of father role expectations and facther role performance of their husbands, most of the respondents anticipated expressive roles as well as traditionally instrumental role from their husbands. Finally, these findings would help us determine family welfare policies in Korea. Improvements in paid and household labor structure of married women should be accomplished at the national level. Also, the acting programs for parent education, marital councelling services, and law enforcement for equal employment between men and women should be provided in our society.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.45 no.4
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• pp.210-216
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• 2022

The army is concerned about the decrease in enlistment resources due to the low birth rate and the weakening of military combat power due to the shortening of the military service period. Now, the military's quantitative growth is no longer limited and it is a time for qualitative growth. To this end, the Army has been applying the Israeli learning method Havruta to recruit training to improve the quality of training since 2019. After applying Havruta, several scholars have studied the effect of recruit training applying Havruta. As a result, it was verified that recruit training applying Havruta improves the inner motive, creativity, and military service value of trainees. This study investigated how trainees' inner motive, creativity, and military service value affect their satisfaction and achievement. In addition, it was studied whether the effect of recruit training applied with Havruta on achievement differs according to the educational background (high school graduate or higher) and military family (professional soldiers within 4th degree) of the trainees. To this end, a survey was conducted on 472 recruits, and the structural relationship between each variable and the moderating effect were analyzed using the structural equation model. As a result of the study, military service value did not affect training satisfaction. Also, there was a difference in the effect of creativity on training satisfaction according to the educational background of new recruits, and there was a difference in the effect of military service value on training satisfaction and training achievement according to military family members. The purpose of this study is to contribute to the improvement of the army's recruit training development plan and effective training system.

• Computers and Concrete
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• v.32 no.2
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• pp.119-138
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• 2023

Concrete carbonation is a prevalent phenomenon that leads to steel reinforcement corrosion in reinforced concrete (RC) structures, thereby decreasing their service life as well as durability. The process of carbonation results in a lower pH level of concrete, resulting in an acidic environment with a pH value below 12. This acidic environment initiates and accelerates the corrosion of steel reinforcement in concrete, rendering it more susceptible to damage and ultimately weakening the overall structural integrity of the RC system. Lower pH values might cause damage to the protective coating of steel, also known as the passive film, thus speeding up the process of corrosion. It is essential to estimate the carbonation factor to reduce the deterioration in concrete structures. A lot of work has gone into developing a carbonation model that is precise and efficient that takes both internal and external factors into account. This study presents an ML-based adaptive-neuro fuzzy inference system (ANFIS) approach to predict the carbonation depth of fly ash (FA)-based concrete structures. Cement content, FA, water-cement ratio, relative humidity, duration, and CO2 level have been used as input parameters to develop the ANFIS model. Six performance indices have been used for finding the accuracy of the developed model and two analytical models. The outcome of the ANFIS model has also been compared with the other models used in this study. The prediction results show that the ANFIS model outperforms analytical models with R-value, MAE, RMSE, and Nash-Sutcliffe efficiency index values of 0.9951, 0.7255 mm, 1.2346 mm, and 0.9957, respectively. Surface plots and sensitivity analysis have also been performed to identify the repercussion of individual features on the carbonation depth of FA-based concrete structures. The developed ANFIS-based model is simple, easy to use, and cost-effective with good accuracy as compared to existing models.

• Ecology and Resilient Infrastructure
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• v.3 no.4
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• pp.272-278
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• 2016

Porous pavements are recommended as a Low-Impact Development (LID) method which is a strategy to develop a water cycle as close to a natural state as possible, and to solve the urban impervious surface problems. Porous pavements can yield a solution if it provides a more permeable surface with extra space to contain extra water from building roofs. But there are few applications in Korea because of a lack of recognition and experience. Highway engineers are mainly concerned about the infiltration of water into pavement structures. They worry about the weakening of the asphalt mixture and subgrade, and freezing during the winter season due to the infiltration of water. Meanwhile, hydrological experts doubt the effects of the amount of water to control during the flooding season, and environmental experts prefer a non-point pollution treatment system established beside highway. In this study, from reviewing the history and the body of literature about porous pavements, conclusions regarding the most advanced technologies were made. First, traditional thickness designs can be used for porous pavement, no extra distresses was found by weakening and freezing during the winter season. Second, hydrological design can be made by controlling the thickness of the pavement and the outlet of water. Third, the treatment efficiency of non-point pollution of porous pavements is not worse than any other method. Importantly, it's a more eco-friendly solution because of its lower requirement for de-icing agents.

• Korean Journal of Food Science and Technology
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• v.46 no.2
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• pp.180-188
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• 2014

This study focused on assessing the solubility and structural characteristics of two types of coenzyme $Q_{10}$ ($CoQ_{10}$) complexes: the $CoQ_{10}$-starch and the $CoQ_{10}$-cyclodextrin complexes. The solubility of $CoQ_{10}$-starch complex increased significantly as the temperature was increased. However, the solubility of $CoQ_{10}$-cyclodextrin complex reached a peak at $37^{\circ}C$, and strong aggregation occurred at $50^{\circ}C$. When the temperature was raised to $80^{\circ}C$, the $CoQ_{10}$-cyclodextrin complex dissociated owing to the weakening of bonds, resulting in $CoQ_{10}$ emerging at the surface of water. Therefore, $CoQ_{10}$-cyclodextrin complexes have lower solubility, due to their reduced heat-stability, than do the $CoQ_{10}$-starch complexes. Structural differences between the two $CoQ_{10}$ complexes were confirmed by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffractometer (XRD), and differential scanning calorimeter (DSC). The $CoQ_{10}$-cyclodextrin complex included an isoprenoid chain of $CoQ_{10}$, while the $CoQ_{10}$-starch complex included both the benzoquinone ring and the isoprenoid chain of $CoQ_{10}$. These results suggest that $CoQ_{10}$-starch complexes possess higher heat-stability and solubility than do the $CoQ_{10}$-cyclodextrin complexes.