• Structural Engineering and Mechanics
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• 제29권3호
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• pp.289-300
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• 2008

The use of metric trial functions to represent the real stress field in what is called the unsymmetric finite element formulation is an effective way to improve predictions from distorted finite elements. This approach works surprisingly well because the use of parametric functions for the test functions satisfies the continuity conditions while the use of metric (Cartesian) shape functions for the trial functions attempts to ensure that the stress representation during finite element computation can retrieve in a best-fit manner, the actual variation of stress in the metric space. However, the issue of how to handle situations where there is locking along with mesh distortion has never been addressed. In this paper, we show that the use of a consistent definition of the constrained strain field in the metric space can ensure a lock-free solution even when there is mesh distortion. The three-noded Timoshenko beam element is used to illustrate the principles. Some significant conclusions are drawn regarding the optimal strategy for finite element modelling where distortion effects and field-consistency requirements have to be reconciled simultaneously.

• Geomechanics and Engineering
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• 제25권4호
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• pp.303-315
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• 2021

A rigorous and generic similarity solution is developed for assessment of the undrained expansion responses of a cylindrical cavity expansion in K₀-consolidated anisotropic soils. A K₀-consolidated anisotropic modified Cam-clay (K₀-AMCC) model that can represent the initial stress anisotropy and the effects of stress-induced anisotropy is used to model the soil behaviors during cavity expansion. All the seven basic unknowns, the three stress components, the pore water pressure, the particle velocity, the specific volume and the hardening parameter, are reduced to the functions of a dimensionless radial coordinate and are taken as coupled variables to formulate the problem. The governing equations are formulated by making use of the equilibrium equation, the constitutive equation, the consistency condition, the continuity condition and the undrained condition, which are then solved as an initial value problem. The proposed rigorous similarity solution is compared with some well-documented rigorous solutions to validate the solution and to highlight the special expansion responses in anisotropic soils. The results reveal that the present solution can yield more predictions for cavity expansion problems in soils with initial anisotropic stresses.

• 지질공학
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• 제33권4호
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• pp.573-586
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• 2023

절리성 암반은 절리 또는 연약면에 의해 역학적인 이방성이 발현될 수 있으며 절리성 암반의 강도 및 변형 특성에 대한 이해는 지질공학 현장에서 주된 관심사이다. 본 연구는 마찰재료로 채택된 석고를 이용하여 단일절리를 포함하는 시료를 성형하고 진삼축시험을 통하여 진삼축 조건의 강도 및 변형 특성을 고찰하였다. 동일한 조건에서 수행한 개별요소법 기반의 삼차원 수치해석은 진삼축시험을 통하여 검증되었으며 타당성이 확보되었다. 수치해석 결과는 절리의 방향성과 더불어 현장의 주응력 조건이 절리성 암반의 강도 및 변형 특성 연구에 있어서 필수적인 요소임을 지시한다. 수치해석을 통하여 절리의 경사각 변화에 따라 산정한 횡등방성 암반의 강도는 중간주응력이 강화함에 따라 유의미한 증가를 나타내며, 증가의 폭은 절리의 경사 조건에 큰 영향을 받는다. 또한, 절리의 경사방향과 두 수평 주응력 방향 간의 상대적인 관계는 횡등방성 암반의 강도특성을 좌우하는 요인이다. 두 개의 절리군을 포함하는 암반의 강도는 경사가 더욱 급한 절리군이 전체 암반의 강도를 좌우한다. 두 절리군 중 한 절리군의 연속성이 짧아 암교 효과를 발휘하면 연속성이 상대적으로 긴 절리군의 방향성이 전체 암반의 강도를 좌우할 수 있다. 절리성 암반에 대한 기존의 삼차원 파괴기준식은 적용성 측면에서 한계도 있지만, 수치해석이 이를 보완하는 데 유용하게 활용될 수 있다.

• Human Ecology Research
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• 제55권4호
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• pp.363-384
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• 2017

The Korean government implemented better support for adolescent single-parent families by expanding the coverage of the Single-parent Family Support Act in 2010. In order to understand the effect, this study verified the moderating effect of the single-parent family policy's support for child rearing in the context of adolescent female single-parent's stress levels and education sustainability. This study utilized part of the National Youth Policy Institute's 'Research on the Actual Condition of the Adolescent Pregnancy, Birth and Rearing Children'. Participants of the study were 248 adolescent single-parents aged 24 and below. The findings and discussion of this study are as follows. First, the stress level of adolescent female single-parent in continuing studies was lower than those for discontinued studies. Students who discontinued their education in the middle of studies showed an increase in life stress level relative to age because they had a low level of education and had discontinued studies before pregnancy. Second, the public nanny service has been verified as an element to increase the continuation of education by controlling the level of stress. It is advisable to fortify and expand the scope of support for childcare services in the form of a study assistant or child education assistant. Last, adolescent single-parent childcare subsidies have been verified as a direct factor that raised the meaningful level of education continuity potential to a meaningful standard that can be seen as a more effective method than general policy support for single-parent families.

• 디지털융복합연구
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• 제19권9호
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• pp.349-360
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• 2021

본 연구의 목적은 청소년 한부모의 스트레스 상황이 학업지속에 미치는 영향에서 여가, 문화, 정보통신 영역에서의 한부모를 위한 사회적 지원이 조절효과를 나타내는 지 검증함에 목적이 있다. 이를 위해 18세 이상의 임신 중인자나 임신해 있으면서 출산 후 자녀를 양육할 계획을 가진 자, 자녀를 낳아 키우고 있는 청소년 한부모 248명을 대상으로 기술통계와 로지스틱 분석을 실시하였다. 그 결과 4명 중 1명이 수혜자로, 청소년 한부모들의 스트레스로 인한 학업 중단 경향을 여가, 문화, 정보통신비 지원이 조절하여 학업지속의 가능성을 증가시키고 있었다. 이러한 결과는 여가, 문화, 정보통신비 지원이 스트레스로 인해 학업을 중단하려는 청소년 한부모의 학업지속 가능성을 높이는 데 효과적으로 기여하고 있음을 보여준다. 따라서 청소년 한부모의 학업지속을 위해 여가와 문화, 정보통신 영역에서의 사회적 지원을 강화할 필요가 있다.

• 터널과지하공간
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• 제17권2호
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• pp.128-138
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• 2007

상대적으로 저심도에 건설되는 암반구조물의 경우 단층이나 절리 등 암반 내 존재하는 불연속면이 굴착 후 생성된 경계면과의 교차에 의해 구조적인 형태의 파괴가 지배적으로 발생하나, 고심도에 건설되는 경우 높은 현지응력과 굴착에 따른 유도응력으로 인해 공동 경계면에서 스폴링이나 슬래빙과 같은 취성파괴가 발생할 수 있다. 취성파괴는 암반구조물의 안정성을 약화시키는 주된 원인으로, 고심도 영역에서 암반구조물의 안정성을 확보하기 위하여 응력조건에 따라 발생하는 취성파괴의 개시시점, 파괴수준 및 파괴범위 등과 같은 파괴특성이 규명되어야 한다. 본 연구에서는 고심도의 암반구조물에서 발생할 수 있는 취성파괴의 파괴수준 및 개시시점과 재하응력사이의 관계를 정량적으로 평가하고자 진삼축 응력조건을 구현할 수 있는 모형실험장치를 설계, 제작하여 여러 응력조건에서 모형실험을 수행하였다. 공동주변에서 발생한 파괴수준을 육안관찰과 미소파괴음 발생양상에 의해 3단계로 구분하고, 진삼축 응력조건에 따라 제시하였다. 그 결과 파괴수준은 공동단면에 작용하는 재하응력$(S_v,\;S_{H2})$ 뿐 아니라 공동 축에 평행한 재하응력 $S_{H1}$에 영향을 받으며, $S_{H1}$와 $S_{H2}$의 크기가 증가할수록 동일한 $S_v$에서 파괴수준은 감소하였다. 파괴개시점 역시 $S_{H1}$와 $S_{H2}$의 증가에 따라 파괴개시를 위한 응력수준은 증가하였으며, 다중회귀분석을 통해 파괴개시시점과 진삼축 응력조건의 관계식을 도출하였다.

• 한국디지털건축인테리어학회논문집
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• 제13권2호
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• pp.17-25
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• 2013

It is important to eliminate thermal bridge for achieving passive and environmental-friendly buildings. Structural members may frequently act as thermal bridges that become a conduit of energy. it is emphasized that thermal bridge breaker (TBB) system is necessary for blocking thermal bridge of the structural members. This TBB system has to maintain a performance to tensile and compressive stress which arises in member section in order to being realized structurally. Thus, it is composed with anchorage devices which obtain continuity with structural members inside building and rebar of cantilever balcony, and compression joint which resist compression stress occurring to TBB. Applying method of TBB's compression joint is designed to have high strength with comparatively small element section which can cover external load. This study carried out finite elements method based on compression experiment. Throughout the FEM analysis, this study provides information on finding optimal shape for compression joint of TBB which can suitably apply to current building balcony of Korea.

• 한국보건간호학회지
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• 제32권3호
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• pp.388-399
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• 2018

Purpose: The aim of this qualitative study was to identify the experiences of smoking and smoking cessation in out-of-school youth. Methods: The participants were 12 out-of-school youths belonging the Youth support Center located in A and B area. The data were collected from January 8 to 15, 2018, using a FGI(Focus Group Interview). The main sub-domains of the experiences of smoking and smoking cessation in out-of-school youth by 7 questions were categorized from the intrapersonal, interpersonal, organizational, and community factors in ecological model. Results: The motivation, continuity, disadvantage of smoking experiences of out-of-school youth were analyzed in 10 sub-domains (curiosity, friend's invitation, mood of adapted group, habit, relieving stress, providing breaks, friendship, physical damage, loss of money, a bad sight of smoker). The reason, difficulty, advantage, reason for restarting smoking cessation experiences of out-of-school youth were analyzed in 15 sub-domains (physical damage, for future hope, invitation of others, influence of family, weight gain, emotional stress, worsening friendship, improvement physical condition, saving money, better relationships, not with bad friends, withdrawal, smoking of friends, drinking, separated a lover). Conclusion: Based on the results, it is expected that a Specialized Smoking Cessation Education Program will be developed for out-of-school youth's health activities in ecological factors.

• Steel and Composite Structures
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• 제49권5호
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• pp.547-570
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• 2023

In the present work, a comparative study has been carried out between power, exponential, and sigmoidal sandwich FGM plates for free vibration conditions under hygro-thermal conditions. Rules of mixture is used to determine effective material properties across the thickness for power-law and sigmoid sandwich FGM plates. Exponential law is used to plot effective material properties for exponentially graded sandwich FGM plates. Temperature and moisture dependent material properties were used during the analysis. Free vibration analysis is carried out using recently proposed finite element based HOZT. Present formulation satisfies interlayer transverse stress continuity conditions at interfaces and transverse shear stress-free conditions at the plate's top and bottom surfaces. The present model is free from any penalty or post-processing requirements. Several new results are reported in the present work, especially for unsymmetric sandwich FGM plates and exponential and sigmoidal sandwich FGM plates.

• Geomechanics and Engineering
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• 제38권6호
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• pp.621-631
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• 2024

In designing earthquake-resistant structures, we traditionally select dynamic loads based on the recurrence period of earthquakes, using individual seismic records or aligning them with the design spectrum. However, these records often represent isolated waveforms lacking continuity, underscoring the need for a deeper understanding of natural seismic phenomena. The Earth's crustal movement, both before and after a significant earthquake, can trigger a series of both minor and major seismic events. These minor earthquakes, which often occur in short time before or after the major seismic events, prompt a critical reassessment of their potential impact on structural design. In this study, we conducted a detailed tunnel response analysis to assess the impact of both single mainshock and multiple earthquake scenarios (including foreshock-mainshock and mainshock-aftershock sequences). Utilizing numerical analysis, we explored how multiple earthquakes affect tunnel deformation. Our findings reveal that sequential seismic events, even those of moderate magnitude, can exert considerable stress on tunnel lining, resulting in heightened bending stress and permanent displacement. This research highlights a significant insight: current seismic design methodologies, which predominantly focus on the largest seismic intensity, may fail to account for the cumulative impact of smaller, yet frequent, seismic events like foreshocks and aftershocks. Our results demonstrate that dynamic analyses considering only a single mainshock are likely to underestimate the potential damage (i.e., ovaling deformation, failure lining, permanent displacement etc.) when compared to analyses that incorporate multiple earthquake scenarios.