Increase in stress on infrastructure facilities due to natural disasters

Juyeong Choi,Abhijeet Deshmukh,Makarand Hastak 서울시립대학교 도시과학연구원 2016 도시과학국제저널 Vol.20 No.2

The services of infrastructure are often compromised in a postdisaster situation. This could be due to a direct physical impact on the infrastructure or due to a cascading impact resulting from reduced services of the supporting infrastructure. The reduced infrastructure services are unable to adequately meet the postdisaster community needs. Therefore, infrastructure facilities are likely to be operated with high stress on their capacities above the allowable stress (i.e. designed capacities) for meeting the services required. The system is unable to sustain the required serviceability level without the infusion of additional capacities when the stress level exceeds the limit stress. For example, after Haiti’s devastating earthquake, disrupted utility services, limited road networks, and the lack of civic governance influenced the capacity of all essential service providers. Furthermore, the earthquake-impacted hospitals had limited resources such as patient beds, medical staff, medical supplies and equipment for meeting the increased health needs of the community. As a result, the hospital experienced increased levels of stress related to services as they were unable to adequately meet the community health needs without external assistance from NGOs or other entities. Therefore, understanding the stress level in postdisaster infrastructure is critical for community recovery. This paper presents a new framework to (i) explore and investigate varying functional stress level in infrastructure under various disaster scenarios and (ii) develop strategies for alleviating increased stress levels in order to facilitate the recovery process. The research framework is explained using a hypothetical situation focusing on the operation of power facilities in a postdisaster situation. The proposed unique approach enables the development of sustainable mitigation strategies by relieving the stress level in critical infrastructure while ensuring to meet recovery demands at an acceptable level.

대학생들의 여가제약과 스트레스 대처 및 삶의 질의 관계

송원익(Song, Won-Ick),황재욱(Hwang, Jae-Wook),오응수(Oh, Eung-Soo) 한국웰니스학회 2016 한국웰니스학회지 Vol.11 No.3

이 연구의 목적은 대학생들의 여가제약과 스트레스 대처 및 삶의 질의 관계를 규명하여, 대학생활의 질적 수준을 향상 시키는 효율적인 방안을 제시하는 동시에 평생 여가활동의 방향을 제시하는데 있다. 연구대상은 대학생 445명을 대상으로 편의표본추출을 통해 여가제약 질문지, 스트레스 대처 질문지, 삶의 질 질문지를 사용하여 연구 절차에 따라 분석하였다. 분석결과, 첫째, 대학생들의 여가제약 스트레스 대처에 부적인 인과관계가 있는 것으로 나타났다. 둘째, 대학생들의 여가제약은 삶의 질에 부적인 인과관계가 있는 것으로 확인되었다. 마지막으로 스트레스 대처와 삶의 질은 정적인 인과관계가 있는 것으로 나타났다. 대학생활의 여가제약은 스트레스 대처와 삶의 질에 부정적인 영향을 미치며, 대학생활의 질적 수준을 낮추는 원인임을 확인하였으며, 여가제약의 부정적인 요인을 잘 분석하여, 대학생들의 여가활동의 중요성을 인식시킬 필요가 있다. The purpose of this study was to investigate relations among leisure limitation, coping stress, and quality of life, and to suggest effective ways to improve quality level of college life and direction of leisure activity in whole life. 445 college students were selected as participants by convenience sampling, and they were done in leisure limitation questionnaire, coping stress questionnaire, and quality of life questionnaire. The data from survey were analyzed through analyzing procedure, and the results of study were as follows, Firstly, leisure limitation in college students had negative casual relationship with coping stress. Secondly, leisure limitation in college students had negative casual relationship with coping stress. Finally, coping stress had positive casual relationship with quality of life. Leisure limitation in college life affected in coping stress and quality of life negatively, and it caused making down of level of quality of college life. Therefore, it needs to analyze a negative factor of leisure limitation, and also it needs to recognize the importance of leisure activity for college students.

DEPENDENCE OF FATIGUE LIMIT OF HIGH-TENSION BOLTS ON MEAN STRESS AND ULTIMATE TENSILE STRENGTH

조성산,장훈,이경우 한국자동차공학회 2009 International journal of automotive technology Vol.10 No.4

High tension bolts in critical joints in internal combustion engines are susceptible to fatigue failure. Computeraided bolted joint design procedures require knowledge of the dependence of bolt fatigue limit on the mean stress and ultimate tensile strength. This dependence is investigated with staircase fatigue limit tests. The test results show that when the bolt fatigue limit is estimated with the nominal stress of the bolt, it decreases with increasing tensile strength and nominal mean stress. However, there is a range of the nominal mean stress where the bolt fatigue limit is almost constant. The test results are interpreted with finite element analysis.

인장하중이 작용하는 평판에 존재하는 반타원 표면균열의 J-적분 계산식

심도준(Do-Jun Shim),김윤재(Yun-Jae Kim),최재붕(Jae-Boong Choi),김영진(Young-Jin Kim),박윤원(Youn-Won Park) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.3

This paper provides a simplified engineering J estimation method for semi-elliptical surface cracked plates in tension, based on the reference stress approach. Note that the essential element of the reference stress approach is the plastic limit load in the definition of the reference stress. However, for surface cracks, the definition of the limit load is ambiguous (local or global limit load), and thus the most relevant limit load (and thus reference stress) for the J estimation should be determined. In the present work, such limit load solution is found by comparing reference stress based J results with those from extensive 3-D finite element analyses. Validation of the proposed equation against FE J results based on actual experimental tensile data of a 304 stainless steel shows excellent agreements not only for the J values at the deepest point but also for those at an arbitrary point along the crack front, including at the surface point. Thus the present results provide a good engineering tool for elastic-plastic fracture analyses of surface cracked plates in tension.

변형 에너지를 이용한 크리프 한계응력강도(S<SUB>t</SUB>)의 결정

김우곤(Woo Gon Kim),이경용(Kyung Yong Lee),윤기봉(Kee Bong Yoon),류우석(Woo Seog Ryu) 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2001 No.8

Creep stress intensity limit(S₁) value for 1% strain in 10? hr was determined using strain energy method based on the work done during creep. For this purpose, 1% creep strain tests for commercial type 316 (J316) and type 316LN (K316LN) stainless steels were conducted with various stress conditions at 550℃ or 593℃. The S₁ value of the K316LN stainless steel was 135 MPa at 550℃ and creep work was 87 KJ/m³. In order to identify reasonability of the strain energy method, the method of isochronus stress-strain curves(ISSC) for the J316 stainless steel was used comparatively. The S₁values for it showed good agreement between two methods. The strain energy method can be simply obtained using only three or four short-term 1% strain data without ISSC obtained by long-term creep data. Particularly, this method is useful in estimation of the stress intensity for new and emerging class of high-temperature materials where creep and tensile data for empirical extrapolation to design life is lacking.

원자로 운전을 위한 압력/온도 한계곡선의 설정

정명조,박윤원 한국전산구조공학회 1997 전산구조공학 Vol.10 No.4

핵분열로 인한 고온, 고압의 냉각수를 유지하는 원자로 용기는 원자로의 냉각 또는 가열시 압력에 의한 응력과 함께 열응력이 가해지고 원자로 벽의 온도변화에 따라 파괴인성치가 변화하기 때문에 임의의 결함이 존재할 경우 건전성 확보가 쉽지 않다. 따라서 가상결함이 성장하지 않도록 압력과 온도를 조정하면서 냉각 및 가열시킬 필요가 있다. 본 연구에서는 원자로 운전 중 냉각 및 가열시 안전하게 운전하기 위한 압력/온도 한계곡선을 구하는 절차에 필요한 이론을 조사하였고 이의 도출을 위한 해석과정을 전산화하였다. 국내원전 중 가장 오래된 고리 1호기에 대한 압력/온도 한계곡선을 다양한 냉각 및 가열률에 따라 설정하였고 이들 결과를 검토하였다. A reactor pressure vessel, which contains fuel assemblies and reactor vessel internals, has the thermal stress resulting from the cool-down and heat-up of the vessel wall in combination with the pressure stress from system pressure resulting in large stresses. The combination of the pressure stress and thermal stress along with a decrease in fracture toughness may cause through-wall propagation of a relatively small crack. Therefore, it is necessary to define the relations between operating pressure and temperature during cool-down and heat-up. In this study, theory of fracture mechanics for a pressure/temperature limit curve is investigated and a numerical procedure for generating it is developed. Plant-specific limit curves for the Kori unit 1 plant, the oldest nuclear power plant in Korea, have been obtained for several cooling and heating rates and their results are discussed.

원자로 운전을 위한 압력/온도 한계곡선의 설정

정명조,박윤원 한국전산구조공학회 1997 한국전산구조공학회논문집 Vol.10 No.4

핵분열로 인한 고온, 고압의 냉각수를 유지하는 원자로 용기는 원자로의 냉각 또는 가열시 압력에 의한 응력과 함께 열응력이 가해지고 원자로 벽의 온도변화에 따라 파괴인성치가 변화하기 때문에 임의의 결함이 존재할 경우 건전성 확보가 쉽지 않다. 따라서 가상결함이 성장하지 않도록 압력과 온도를 조정하면서 냉각 및 가열시킬 필요가 있다. 본 연구에서는 원자로 운전 중 냉각 및 가열시 안전하게 운전하기 위한 압력/온도 한계곡선을 구하는 절차에 필요한 이론을 조사하였고 이의 도출을 위한 해석과정을 전산화하였다. 국내원전 중 가장 오래된 고리 1호기에 대한 압력/온도 한계곡선을 다양한 냉각 및 가열률에 따라 설정하였고 이들 결과를 검토하였다. A reactor pressure vessel, which contains fuel assemblies and reactor vessel internals, has the thermal stress resulting from the cool-down and heat-up of the vessel wall in combination with the pressure stress from system pressure resulting in large stresses. The combination of the pressure stress and thermal stress along with a decrease in fracture toughness may cause through-wall propagation of a relatively small crack. Therefore, it is necessary to define the relations between operating pressure and temperature during cool-down and heat-up. In this study, theory of fracture mechanics for a pressure/temperature limit curve is investigated and a numerical procedure for generating it is developed. Plant-specific limit curves for the Kori unit 1 plant, the oldest nuclear power plant in Korea, have been obtained for several cooling and heating rates and their results are discussed.

Recent Progress in Strain-Engineered Stretchable Constructs

Adeela Hanif,Donghyeon Yoo,Dohui Kim,Farid Mustafayev,Sarkhan Hajiyev,Dong Sung Kim 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.11 No.4

A variety of natural biological tissues (e.g., skin, ligaments, and blood vessels) exhibit a J-shaped stress–strain behavior, combining soft, compliant mechanics and large levels of stretchability together with a natural ‘strain-limiting’ mechanism to prevent damage from excessive strain. This review provides an extensive overview of recent advancements in the field of strain-engineered stretchable constructs, with a particular emphasis on strain-limiting constructs mimicking the J-shaped stress–strain behavior. The use of synthetic materials that have a similar stress–strain behavior to the target could be helpful for many potential applications, such as tissue engineering (to simulate the J-shaped nonlinear mechanical properties of biological tissues) and biomedical devices (to enable natural, comfortable integration of stretchable electronics with biological tissues/organs). In recent years, several studies have been conducted on these constructs because of their exceptional ability to withstand large deformations with electrical stability in stretchable and wearable electronics. One of the purposes of this review is to summarize the recent fabrication approaches used for developing strain-engineered stretchable constructs mimicking the J-shaped stress–strain/strain-limiting behavior of biological tissues. The review also highlights recent applications of strain-limiting constructs, which have shown their potential in incorporating into a broad range of innovative fields, such as soft robotics, biomedical devices, wearable and stretchable electronics, and human–machine interfaces. Lastly, we concluded the review by pointing out some limitations and future prospective of the strain-engineered stretchable constructs.

Measurement reliability of irreversible stress/strain limits in Sn-Cu double layer stabilized IBAD/RCE-DR processed GdBCO coated conductor tapes under uniaxial tension at 77 K

Bautista, Zhierwinjay,Diaz, Mark Angelo,Shin, Hyung-Seop,Lee, Jae-Hun The Korean Society of Superconductivity and Cryoge 2018 한국초전도저온공학회논문지 Vol.20 No.4

In this study, the electromechanical properties in Sn-Cu double layer stabilized GdBCO coated conductor (CC) tapes with and without external lamination under uniaxial tension were examined at 77 K and self-field. Their irreversible stress and strain limits were determined using a loading-unloading scheme based on different critical current ($I_c$) recovery criteria. The repeated tests were performed and statistical estimation was done to check the reproducibility depending on the criterion adopted in evaluating the electromechanical properties. From the results, it showed that the Sn-Cu double-layer stabilized CC tapes have the higher irreversible stress limit, but lower irreversible strain limit as compared to brass laminated ones. Through the repeated tests, it can be found that a small scattering of irreversible limits existed in both CC tape samples. Finally, similar strain sensitivity of $I_c$ in both CC tapes was obtained.

Measurement reliability of irreversible stress/strain limits in Sn-Cu double layer stabilized IBAD/RCE-DR processed GdBCO coated conductor tapes under uniaxial tension at 77 K

Zhierwinjay Bautista,Mark Angelo Diaz,신형섭,이재훈 한국초전도.저온공학회 2018 한국초전도저온공학회논문지 Vol.20 No.4

In this study, the electromechanical properties in Sn-Cu double layer stabilized GdBCO coated conductor (CC) tapes with and without external lamination under uniaxial tension were examined at 77 K and self-field. Their irreversible stress and strain limits were determined using a loading-unloading scheme based on different critical current (Ic) recovery criteria. The repeated tests were performed and statistical estimation was done to check the reproducibility depending on the criterion adopted in evaluating the electromechanical properties. From the results, it showed that the Sn-Cu double-layer stabilized CC tapes have the higher irreversible stress limit, but lower irreversible strain limit as compared to brass laminated ones. Through the repeated tests, it can be found that a small scattering of irreversible limits existed in both CC tape samples. Finally, similar strain sensitivity of Ic in both CC tapes was obtained.