• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.1
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• pp.65-72
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• 1983

Dry sand specimens for both normally consolidated and overconsolidated triaxial compression tests were prestressed on the path with five different coefficients of earth pressure 1.0, 3/4, 0.55, $K_0$ and 1/3. Deformation resistance of normally consolidated sand increased with increasing the initial stress for all coefficients of earth pressure during consolidation, and the deformation modulus at a certain initial stress showed a tendency to increase with increasing the coefficient of earth pressure. And deformation moduli($E_i$, $E_{50}$), were found to be proportional to the $n_{th}$ power of initial stresses[${\sigma}_{m0}{^{\prime}}$, ${\sigma}_{10}{^{\prime}}$, ${\sigma}_{30}{^{\prime}}$, $({\sigma}_1-{\sigma}_3)_0$] for both isotropically and anisotropically normally consolidated samples, where n varied from 0.37 to 0.92. Overconsolidated sand with the higher overconsolidation ratio showed the higher deformation modulus. It is concluded that the $K_0$-anisotropically consolidated triaxial compression test is necessary to obtain the more accurate value of in-situ deformation modulus.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5D
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• pp.831-838
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• 2006

An experimental/analytic study has been conducted to understand the adverse effects of low vehicle speed, high axle load and high tire pressure on the performance of asphalt pavements. Of 33 asphalt sections at KHC test road, two sections having different base layer thickness (180 mm versus 280 mm) are adopted for rollover tests. During the test, a standard three-axle dump truck maintains a steady state condition as moving along the wheel path of a passing lane, and lateral offsets and real travel speed are measured with a laser-based wandering system. Test results suggest that vehicle speed affects both longitudinal and transverse strains at the bottom of asphalt layer (290 mm and 390 mm below the surface), and even slightly influences the measured vertical stresses at the top of subbase and subgrade due to the dynamic effect of rolling vehicle. Since the anisotropic nature of asphalt-aggregate mixtures, the difference between longitudinal and transverse strains appears prominent throughout the measurements. As the thickness of asphalt pavement increases, the measured lateral strains become larger than its corresponding longitudinal strains. Over the limited testing conditions, it is concluded that higher axle weight and higher tire pressures induce more strains and vertical stresses, leading to a premature deterioration of pavements. Finally, a layered elastic analysis overestimates the maximum strains measured under the 1st axle load, while underestimating the maximum vertical stress in both pavement sections.

• Korean Journal of Human Ecology
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• v.6 no.1
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• pp.15-27
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• 1997

The purpose of this study was to examine the effects from social supports and global self-worth on stresses for the children. The subjects were 438 children of the 5th grade in Elementary School and the first grade in Junior High School in Taejeon. The instruments used for this study were Children's Social Support, Global Self-Worth and Stress Scale. The data were analyzed using t-test, Pearson's correlation, multiple regression and path analysis. The main results of the study were as follows; 1. The stresses were different depending on age. When the family and the teacher give higher social supports, the 5th graders have higher global self-worth. When the family gives higher social supports, the stresses were decreased for the 5th graders. When the children have higher global self-worth, the stresses were decreased. 2. When the first graders in Junior High School experienced higher global self-worth and social supports from their friends, family, teacher, the stresses were decreased. 3. The first graders in Junior High School experienced more stresses than the 5th graders in Elementary School in parent-related and academic-related domains. But the first graders in Junior High School experienced less stresses than the 5th graders in Elementary School in friend-related domains. 4. The path analysis showed that social supports from friends and family explained 15% of the stresses for the 5th graders in elementary school. Social support from friends, family, and teacher explained 28% of the stresses for the first graders in Junior High School. 5. For the 5th graders in Elementary School, social supports from friends and family had direct influences on the global self-worth. And the global self-worth had direct influence on children's stresses. But for the first graders in Junior High School, social supports from friends, family, and teacher had direct influences on the global self-worth. And the social supports from friends had direct and indirect effects on children's stresses. 6. For predicting the stresses, the most significant variable was the global self-worth for the 5th graders in Elementary School and the first graders in Junior High School.

• Journal of the Architectural Institute of Korea Planning & Design
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• v.34 no.11
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• pp.85-94
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• 2018

This study aims to investigate how easy pedestrians get around within/through the "Apartment Complexes (AC), " a common style of high-rise multi-family housing in Korea. Over the past six decades, the AC has been the most conventional way to provide standardized housing efficiently to address the problems of the shortage of housing and the substandard housing, due to the explosion of urban population with the rapid industrialization. The AC is a huge chunk of homeogenous multi-family housing, mostly condos with decent infrastructure, including parks, pedestrian passages, schools, ect. Both in the new town development and urban renewal programs have utilized the advantages of the AC. Since the design principals of AC tend to adopt the "protective design" to prevent cars and pedestrians coming outside from passing it, it has been criticised for dissecting the continuity of socioeconomic context in neighborhoods. The neo-traditional planning urbanists, including Jane Jacobs, emphasize that smaller blocks and grid road newtworks are the key in improving social, cultural, and economic vitality of the neighborhoods, because these design concepts allow more pedestrians and different types of people to be mixed in a neighborhood. In this study, we first adopted objective measures for pedestrian accessibility and pedestrian efficiency. These measures were used to calculate the lengths of shortest paths from residential buildings to the edges of AC. We tested the difference in shortest paths between the current pedestrian networks of AC and hypothetical grid networks on the AC, and the relative difference is considered as the pedestrian efficiency, using the network analysis function of Geographic Information Systems (GIS) and Python programming. We found from the randomly selected 30 ACs that the existing non-grid road networks in ACs are worse than the hypothesized grid networks, in terms of pedestrian efficiency. In average, pedestrians in AC with the conventional road networks have to walk than 25%, 26%, and 27% longer than the networks of $125{\times}45m$, $100{\times}45m$, and $75{\times}45m$, respectively. With the t-test analysis, we found the pedestrian efficiency of AC with the conventional network is lower than grid-networks. Many new urbanists stress, easiness of walking is one of the most import elements for community building and social bonds. With the findings from the objective measures of pedestrian accessibility and efficiency, the AC would have limitations to attract people outside into the AC itself, which would increase dis-connectivity with adjacent areas.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.2
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• pp.55-64
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• 1984

Presented is a nonlinear constitutive model for progressive tensile fracturing of concrete. The model is incremental, path-dependent, and tensorialy invariant. The total strain tensor is assumed to be a sum of a purely elastic component and an inelastic component. The material is considered to contain weak planes of all directions which characterize the planes of the microcracks. A one-to-one functional dependence is assumed between the normal stress and the normal strain across each of the weak planes. The tangential stiffness of concrete is then derived form the principle of virtual work. The present theory can be applied to loading histories which are nonproportional or during which the principal directions rotate. Good agreement with the available direct tensile test data which cover strain-softening is demonstrated.

• Journal of Korean Academy of Nursing
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• v.48 no.5
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• pp.565-577
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• 2018

Purpose: The purpose of this study was to construct and test a hypothetical model about impact of parents' problem drinking on suicidal ideation of their children who are university students and the multiple mediating effects of childhood trauma, experiential avoidance, and depression based on stress-vulnerability model. Methods: A purposive sample of 400 university students was recruited from three universities in provincial areas and the data were collected between October and November 2016. The collected data were then analyzed using SPSS 20.0 and AMOS 20.0 programs. For data analysis, descriptive statistics, factor analysis, and structural equation modeling were performed. Multiple mediating effects analysis using phantom variable and bootstrapping were implemented to verify the mediating effect of the research model. Results: We found no significant direct effect on depression and suicidal ideation of parents' problem drinking, but multiple mediating effects of childhood trauma and experiential avoidance between parents' problem drinking and depression (B=.38, p=.001). The path from parents' problem drinking to suicidal ideation was significantly mediated by childhood trauma and depression (B=.02, p=.016) and by childhood trauma, experiential avoidance, and depression (B=.05, p=.011), but experiential avoidance did not have a significant direct effect on suicidal ideation (B=.02, p=.616). Conclusions: Based on the results of this study, it can be suggested that in order to decrease depression and prevent suicide of university students, considering of parents' problem drinking and childhood trauma, intervention methods that decreased chronic use of experiential avoidance and strengthen acceptance should be developed and made available to them.

• Journal of the Korean Geotechnical Society
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• v.20 no.5
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• pp.145-159
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• 2004

The conventional method for assessment of liquefaction potential proposed by Seed and Idriss has been widely used in most countries because of simplicity of tests. Even though various data such as stress, strain, stress path, and excess pore water pressure can be obtained from the dynamic test, especially, two simple experimental data such as the maximum deviatoric stress and the number of cycles at liquefaction have been used in the conventional assessment. In this study, a new detailed assessment for liquefaction potential to reflect both characteristics of real earthquake motion and dynamic soil resistance is proposed and verified. In the assessment, the safety factor of the liquefaction potential at a given depth of a site can be obtained by the ratio of a resistible cumulative plastic shear strain determined through the performance of the conventional cyclic test and a driving cumulative plastic shear strain calculated from the shear strain time history through the ground response analysis. The last point to cumulate the driving plastic shear strain to initiate soil liquefaction is important for this assessment. From the result of cyclic triaxial test using real earthquake motions, it was concluded that liquefaction under the impact-type earthquake loads would initiate as soon as a peak loading signal was reached. The driving cumulative plastic shear strain, therefore, can be determined by adding all plastic shear strains obtained from the ground response analysis up to the peak point. Through the verification of the proposed assessment, it can be concluded that the proposed assessment for liquefaction potential can be a progressive method to reflect both characteristics of the unique soil resistance and earthquake parameters such as peak earthquake signal, significant duration time, earthquake loading type, and magnitude.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.3
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• pp.43-52
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• 1984

This paper is concerned with the strain characteristics of the time effect on the remoulded saturated day sampled from the downstream of the Yeongsan river, and the constitutive equation that can generally explain time-dependent behaviors of norma1ly consolidated clay. This paper examines whether or not the afore-said constitutive equation can be applied to the remoulded Mooan-clay. Throughout this study, the conclusions obtained are as follows. 1. Throughout the isotropic consolidation test for 7 days and the isotropic relaxation test, the existence of the static and dynamic yielding surfaces is confirmed respectively. 2. The characteristics of time effect of the deformation, namely, the existence of a unique stress-strain-time relation, is conformed from the experimental result on the Mooan-clay. 3. The prodictions of the stress path and the strain on the Cam-clay theory is not consistent with those observed during the experiments. 4. Constitutive equation(2-3-12) obtained by applying Cam-clay theory to Perzyna's elastic-viscoplasticity theory can explain the behavior of pore water pressure during isotropic stress relaxation, concerned with time dependency under undrained condition. The equation can also explain the results of the undrained triaxial compression test for the clay with different strain rate under the same or different consolidation history. 5. This constitutive equation has eight material parameters which can be determined from triaxial compression tests.

• Korean Journal of Social Welfare
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• v.58 no.1
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• pp.59-85
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• 2006

The purpose of this study was to identify how traumatic experiences and stresses caused hopelessness and depression among low-income residents, and to delineate what social problem solving capabilities might play roles in relation to the hopelessness theory of depression. For the purpose of the study, the target group of this study was restricted to adults over 20. This study recruited 175 low-income residents(the Beneficiary of National Basic Livelihood Security Act and the Near Poor Group) in Busan, Korea and employed a self-administered survey method during February, 2004. The following are the major results of the study. First, in low-income subjects, stresses showed positive influences on hopelessness. Second, in low-income subjects, stresses and hopelessness showed positive influences on depression. Third, stress influenced depression with hopelessness as the intervening variable, but it was not statistically significant path in traumatic experiences. The hopelessness theory of depression is to test whether the individuals who have negative attributional style and experience negative life events are likely to make negative attributions for the negative events they confront. The present study, using low-income residents, found that negative life experience predict negative attributions without negative attributional style. Fourth, social problem solving capabilities buffered the relationship between stress and hopelessness. It was also significant subscales apart from Positive Problem Orientation and Negative Problem Orientation. Fifth, social problem solving capabilities buffered the relationship between hopelessness and depression. It was also significant subscales apart from Negative Problem Orientation and Impulsivity/Carelessness Style. Based on the results, practice implications by identifying what social problem solving capabilities might play roles in hopelessness theory of depression were discussed.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.247-256
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• 2003

FEM analyses which are based on modified Cam-clay theory have been generally used in such cases as analyses of stability and displacement fur embankment construction on soft clays. However, the Modified Cam Clay Model can generate some problems in anisotropic stress conditions of field because the critical state theory has been developed through many laboratory tests in isotropic conditions. Thus, the applicability on the prediction of undrained shear strength and pore water pressure which was based on the critical state theory was evaluated by triaxial tests and numerical analyses in isotropic and anisotropic conditions. Used samples often come out in domestic area, together with general low plastic clays which are showing dilatant behavior in shearing process. They were evaluated by laboratory tests and FEM based on MCCM. From the results of test and numerical analysis, the predictions of undrained strength in low plastic clays well coincided with each other in both isotropic and anisotropic conditions. However, the generation of porewater pressure was often overestimated during undrained shearing in anisotropic conditions. The results can generate the errors in the prediction of stress path of field sites during loading such as construction of embankment on soft clays because the field is subjected to anisotropic conditions during loading.