• Advances in concrete construction
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• 제10권4호
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• pp.289-299
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• 2020

A reliability analysis of the axial compressive load bearing capacity of postfire reinforced concrete (RC) columns strengthened with carbon fiber reinforced polymer (CFRP) sheets was presented. A 3D finite element (FE) model was built for heat transfer analysis using software ABAQUS. Based on the temperature distribution obtained from the FE analysis, the residual axial compressive load bearing capacity of RC columns was worked out using the section method. Formulas for calculating the residual axial compressive load bearing capacity of the columns after fire exposure and the axial compressive load bearing capacity of postfire columns retrofitted with CFRP sheets were developed. Then the Monte Carlo method was used to analyze the reliability of the axial compressive load bearing capacity of the RC columns retrofitted with CFRP sheets using a code developed in MATLAB. The effects of fire exposure time, load ratio, number of CFRP layers, concrete cover thickness, and longitudinal reinforcement ratio on the reliability of the axial compressive load bearing capacity of the columns after fire were investigated. The results show that within 60 minutes of fire exposure time, the reliability index of the RC columns after retrofitting with two layers of CFRPs can meet the requirements of Chinese code GB 50068 (GB 2001) for safety level II. This method is effective and accurate for the reliability analysis of the axial load bearing capacity of postfire reinforced concrete columns retrofitted with CFRP.

• 한국경제지리학회지
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• 제25권2호
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• pp.219-236
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• 2022

1950년대 이후 선진공업국에서 나타난 탈 공업화 현상과 1970년대의 석유위기 이후의 경제위기에서 탈피하기 위한 대안 중 하나는 첨단 신산업을 중심으로 지역혁신을 유도하는 것이었다. 미국의 실리콘 밸리, 영국의 캠브리지 등은 체계적인 계획이나 정책적 노력 없이 혁신환경이 조성된 대표적인 예라고 할 때, 옥스퍼드 지역 역시 그에 버금가는 혁신지역이라 할 수 있다. 본 연구는 옥스퍼드 지역을 대상으로 지역혁신이 언제, 어떠한 방식으로 발생하였으며, 그러한 변화과정에 영향을 미치는 요소는 무엇인지, 혁신은 어떻게 시작되었는지 등을 규명하고자 한다. 본 연구는 여러 가지 문헌자료와 인터넷 포탈 등을 검색하고 현장답사를 통한 관계자, 전문가 면담 등을 통해 수집한 자료에 근거하여 이루어졌다.

• Computers and Concrete
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• 제26권2호
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• pp.115-125
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• 2020

To reduce the damage of concrete in fire, a new type of lightweight cinder aggregate concrete was developed due to the excellent fire resistance of cinder. To further enhance its fire resistance, Polypropylene (PP) Fibers which can enhance the fire resistance of concrete were also used in this type of concrete. However, the bond behavior of this new type of concrete after fire exposure is still unknown. To investigate its bond behavior, 185 specimens were heated up to 22, 200, 400, 600 or 800℃ for 2 h duration respectively, which is followed by subsequent compressive and tensile tests at room temperature. The concrete-rebar bond strength of C30 PP fiber-reinforced cinder concrete was subsequently investigated through pull-out tests after fire exposure. The microstructures of the PP fiber-reinforced cinder concrete and the status of the PP fibre at different temperature were inspected using an advanced scanning electron microscopy, aiming to understand the mechanism of the bonding deterioration under high temperature. The effects of rebar diameter and bond length on the bond strength of PP fiber-reinforced cinder concrete were investigated based on the test results. The bond-slip relation of PP fiber-reinforced cinder concrete after exposure at different temperature was derived based on the test results.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.745-755
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• 2010

GTX(Great Train Express), the wide area express train of a big city center of metropolitan area, is the best new transportation method able to realize 'Low Carbon Green Growth' for solving traffic congestion of the metropolitan area with the connection the metropolitan area into 40-minute life zone by speeding up the standardized velocity, making the route straight and reducing the compensation of land using the space of 40~50m below the ground. In the transportation sector all over the world, if it turned into the public transportation system focusing on the train at a point of time that low carbon green revolution takes the initiative, national competitiveness would be enhanced by reducing the emission of carbon from cars by 1/6. Accordingly, this study is to look into the efficient operation in accordance with GTX construction superintended by currently Gyeonggi province and to consider the optimum operation plan of GTX that are proper for the actual circumstances of the country by comparatively analyzing overseas cases that took their positions as new transportation by curtailment of transit time through highspeed such as London area, Paris area, and Tokyo area etc that are similar to Korean metropolitan area.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권2호
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• pp.796-808
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• 2019

In this paper, a Smoothed Particle Hydrodynamics (SPH) method is extended to simulate the ice failure process and ice-ship interactions. The softening elastoplastic model integrating Drucker-Prager yield criterion is embedded into the SPH method to simulate the failure progress of ice. To verify the accuracy of the proposed SPH method, two benchmarks are presented, which include the elastic vibration of a cantilever beam and three-point bending failure of the ice beam. The good agreement between the obtained numerical results and experimental data indicates that the presented SPH method can give the reliable and accurate results for simulating the ice failure progress. On this basis, the extended SPH method is employed to simulate level ice interacting with sloping structure and three-dimensional ice-ship interaction in level ice, and the numerical data is validated through comparing with experimental results of a 1:20 scaled Araon icebreaker model. It is shown the proposed SPH model can satisfactorily predict the ice breaking process and ice breaking resistance on ships in ice-ship interaction.

• International Journal of Naval Architecture and Ocean Engineering
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• 제10권3호
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• pp.329-347
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• 2018

The Smoothed Particle Hydrodynamics (SPH) method has proved to have great potentials in dealing with the wave-structure interactions. Compared with the Weakly Compressible SPH (WCSPH) method, the ISPH approach solves the pressure by using the pressure Poisson equation rather than the equation of state. This could provide a more stable and accurate pressure field that is important in the study of wave-structure interactions. This paper improves the solid boundary treatment of ISPH by using a high accuracy Simplified Finite Difference Interpolation (SFDI) scheme for the 2D wave-structure coupling problems, especially for free-moving structure. The proposed method is referred as the ISPH_BS. The model improvement is demonstrated by the documented benchmark tests and laboratory experiment covering various wave-structure interaction applications.

• 대한지리학회지
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• 제49권2호
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• pp.299-309
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• 2014

재개발과정에서 상가세입자의 보상과 강제철거문제에 대한 관심이 증가하고 있다. 본 연구는 왜 상가세입자들이 재개발에 저항하며 단체운동을 하지 않는지 어떻게 그들의 권리를 향상시킬 수 있는가에 초점을 두고 있다. 용산의 한 재개발 지역을 대상으로 사례연구를 진행하였다. 도시재개발 계획이 세입자들에게 많은 문제점을 야기함에도 불구하고, 세입자들이 도시재개발 의사결정과정에 참여할 기회가 전무하다. 상가세입자들은 개인적으로 집단적으로 지역정치에 미치는 영향력이 미약한 탓에 도시재개발제도를 변화시킬 충분한 기회를 갖지 못한다. 도시재개발영역에서 상가세입자의 무력함으로 인해 많은 세입자들이 젠트리피케이션 반대운동에 소극적이거나 냉담하였다. 구조적인 부정의 문제를 해결하기 위해서는 세입자 보호를 위한 강력한 법률개정과 더불어 도시에 대한 권리에 대한 세입자들의 의식을 향상시키는 것이 중요하다.

• 한국대기환경학회지
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• 제8권1호
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• pp.1-6
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• 1992

Using data measured in 1989, a study on variations of visibility and air pollution observed in Seoul, Chongju and Choopoongryong is carried out. Analysis includes on low visibility (< 10km) and smog occurring in the Metropolitan Seoul. It was observed that number of days of visibility less than 10km during 1989 was 56.7% (207 days) for Seoul, 45.7%(167 days) for Chongju and 5.8% (21 days) for Choopoongryong. Chongju is a medium size city (population : a half million) and Choopoongryong is a rural site. In the urban are as, however, the number of low visibility days was relatively large during the winter but with little seasonal variations. In each month these cities recorded more than 10 days of low visibility. The visibility reduction due to mist, fog and haze been occurred with air pollution. In particular, the reduction in a cold season related with an increase in high concentrations of $SO_x$ and aerosols. This type of low visibility occurring in Seoul is a similar type that is occurring in London, U.K. On the other hand, the visibility reduction during in a warm season is related with high concentrations of NOx and other photochemical precursors. The visibility reduction in Seoul during summer is the same type occurring in Los Angeles, U.S.A.

• The Journal of Asian Finance, Economics and Business
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• 제8권5호
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• pp.201-210
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• 2021

COVID-19 presented the world with a severe loss of life and impact, which has no geographical bounds or expected time to when its effects will subside. It has affected countries across the globe, disrupting economic levels and businesses in every industry while also altering individuals' everyday lives. The current research aims to examine the impact of coronavirus pandemic on entrepreneur's business activities and their perceptions on the difference in consumer behavior during this time. The findings reveal the pandemic negatively impacted business productivity and profits, forcing many businesses to physically close permanently. Surprisingly, female entrepreneurs do not perceive a change in consumer behavior compared to pre-COVID-19 times. Interestingly, the results indicate there is a negative impact on employees' efficiency to conduct work in which almost no research has conveyed such a finding. For this purpose, a survey was conducted with 445 responses from male and female entrepreneurs in the capital city of Riyadh, Saudi Arabia, using a simple random sample over the period of four months. Ultimately, this research will help entrepreneurs gain more knowledge and a deeper understanding of this new environment necessary to undertaking certain measures and adaptability in order to sustain their businesses during unprecedented times.

• Coupled systems mechanics
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• 제6권2호
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• pp.189-206
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• 2017

Tanks are used to store a wide variety of liquids such as oil, gasoline and water. It is reported that, a large number of tanks have been damaged during severe earthquakes. Therefore, understanding their behavior under earthquake is an important subject for structural engineers. In this paper, a comprehensive study is presented on dynamic response of tanks. A parametric study has been completed on the rectangular storage tanks with aid of finite element method (FEM). Various parameters are investigated, such as; liquid height, density and earthquake with different peak ground acceleration (PGA). When investigating these parameters, modal and time history method is used. Six different earthquake records are used for time history analysis. The analysis results show that when the PGA increases by 10.7 times, the maximum displacements, stress, sloshing and base shear increase by 11.4, 22.6, 5.46 and 17.8 times, respectively and when the liquid height increases by two times, the absolute maximum values of stress, displacements, base shear and sloshing increase 1.65, 2.04, 2.05 and 1.34. Furthermore, values of sloshing increase with decrease in density.