• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2011년도 춘계 학술논문 발표대회 1부
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• pp.27-30
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• 2011

Analysis data of basics which are used for LCC(Life Cycle Cost) analysis of buildings and maintenance plan, are demanded to secure according as replacement cycle of repairs of apartment houses has come. However, investigation techniques and systems for investigating condition of deterioration of apartment houses, have not been made yet in Korea. For this reason, this study was wanted to make investigation techniques and systems, so the process for maintenance of apartment houses was researched and the required quality and deterioration factors of interior/exterior materials were investigated. As a result Check-List for investigating condition of deterioration, was made. if this is used during a nonscheduled, a routine, a regular and a urgency check, the methodical investigation will be achieved. Furthermore, if this is used for maintenance of apartment houses, it will be helped to select the repair cycle and the long-term repair plan.

• 국제학술발표논문집
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• The 3th International Conference on Construction Engineering and Project Management
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• pp.1630-1636
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• 2009

Nine alkali-activated (AA) mortars were mixed and cured at water or air-dried conditions to explore the significance and limitation for the application of the combination of Ba and Ca ions as an alkali-activator. Ground granulated blast-furnace slag (GGBS) was used for source materials, and calcium hydroxide (Ca(OH)₂) and barium hydroxide (Ba(OH)₂) were employed as alkali activators. Test results clearly showed that the water curing condition was more effective than the air-dried curing condition for the formation of the denser calcium silicate hydrate (C-S-H) gels that had a higher molar Si/Ca ratio, resulting in a higher strength development. At the same time, the introduction of Ba(OH)₂ led to the formation of 2CaO·Al₂O₃·SiO₂·8H₂O (C₂ASH₈) hydrates with higher molar Si/Al and Ca/Al ratios. Based on the test results, it can be concluded that the developed cementless mortars have highly effective performance and high potential as an eco-friendly sustainable building material.

• Geomechanics and Engineering
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• 제32권2호
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• pp.179-191
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• 2023

To study the influences of tunneling on the earth pressure and ground settlement when the tunnel passes through the adjacent underground retaining structure, 30 two-dimensional model tests were carried out taking into account the ratios of tunnel excavation depth (H) to lateral width (w), excavation width (B), and excavation distance using a custom-made test device and an analogical soil. Tunnel crossing adjacent existing retaining structure (TCE) and tunnel crossing adjacent newly-built retaining structure (TCN) were simulated and the earth pressure variations and ground settlement distribution during excavation were analyzed. For TCE condition, the earth pressure increments, maximum ground settlement and the curvature of the ground settlement curve are negatively related to H/B, but positively related to H/s and H/w. For TCN condition, most trends are consistent with TCE except that the earth pressure increments and the curvature of ground settlement curve are negatively related to H/w. The maximum ground settlement is larger than that observed in tunnel crossing the existing underground structure. This study provides an assessment basis for the design and construction under confined space conditions.

• 천문학회보
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• 제44권2호
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• pp.71.3-71.3
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• 2019

Previously we developed a method of coronal force-free field construction using vector potentials. In this method, the boundary normal component of the vector potential should be adjusted at every iteration step to implement the boundary normal current density, which is provided by observations. The method was a variational method in the sense that the excessive kinetic energy is removed from the system at every iteration step. The boundary condition imposing the normal current density, however, is not compatible with the variational procedure seeking for the minimum energy state, which is employed by most force-free field solvers currently being used. To resolve this problem, we have developed a totally new method of force-free field construction. Our new method uses a unique magnetic field description using two scalar functions. Our procedure is non-variational and can impose the boundary normal current density exactly. We have tested the new force-free solver for standard Low & Lou fields and Titov-Demoulin flux ropes. Our code excels others in both examples, especially in Titov-Demoulin flux ropes, for which most codes available now yield poor results. Application to a real active region will also be presented.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2013년도 춘계 학술논문 발표대회
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• pp.46-47
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• 2013

This study investigates the effect of a grading of aggregate on the properties of concrete. It is a common sense in Korea that the production of coarse aggregate in ready mixed concrete industry excludes particular aggregate size ranged from 5 mm to 13 mm for saving the production cost. This causes a gap grading of the aggregate for concrete, which can lead to the increase of unit water, the development of drying shrinkage-induced crack and the reduction of compressive strength. In this study, conventional aggregate obtained from a ready mixed concrete factory and the aggregate with a modified grading produced in lab. condition were prepared. Results showed that a good grading of aggregate (i.e., the ratio of 5~13 mm and 13~25 mm is 6 to 4) produced in the lab. condition significantly improved the slump and the compressive strength of the concrete.

• Structural Monitoring and Maintenance
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• 제10권2호
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• pp.155-174
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• 2023

High performance concrete (HPC) has been extensively used in thin overlay for repair purpose due to its excellent strength and durability. This paper presents an experiment, where the sensor-instrumented HPC overlays have been followed by dynamic strain and moisture content monitoring for 1 year, under normal traffic. The vibrating wire and soil moisture sensors were embedded in overlay before construction. Four given HPC mixes (2 original mixes and their shrinkage-modified mixes) were used for overlays to contrast the strain and moisture results. A calibration method to accurately measure the moisture content for a given concrete mixture using soil moisture sensor was established. The monitoring results indicated that the modified mixes performed much better than the original mixes in shrinkage cracking control. Weather condition and concrete maturity at early age greatly affected the strain in concrete. The strain in HPC overlay was primarily in longitudinal direction, leading to transverse cracks. Additionally, the most moisture loss in concrete occurred at early age. Its rate was very dependent on weather. After one year, cracking survey was carried out by vision to verify the strain direction and no cracks observed in shrinkage modified mixes.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.309-310
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• 2023

Slag and ash generally have a higher powder degree than portland cement, so workability may deteriorate under the same unit quantity condition, and strength and durability decrease when the unit quantity is increased. At this time, if an aggregate having a low water absorption and an appropriate particle size is used to recover the loss of strength, it can contribute to reducing the unit quantity of the binder. Therefore, for the purpose of improving the workability and strength of non-sintered cement mortar using slag and ash, ferro nikel slag whose particle size was adjusted was used as an aggregate and its applicability was identified. In this experimental condition, it was confirmed that non-sintered cement mortar tends to improve workability and secure strength when ferro nikel slag having various particle size distributions is used as an aggregate. This can be analyzed as the effect of ferro nikel slag material properties including glassy properties and mixing conditions with a wide particle size distribution.

• Smart Structures and Systems
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• 제32권6호
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• pp.359-369
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• 2023

Servo-motor driven uniaxial shake tables have been widely used for education and research purposes in earthquake engineering. These shake tables are mostly displacement-controlled by a digital proportional-integral-derivative (PID) controller; however, accurate reproduction of acceleration time histories is not guaranteed. In this study, a control strategy is proposed and verified for uniaxial shake tables driven by a servo-motor. This strategy incorporates a deep-learning algorithm named Long Short-Term Memory (LSTM) network into a displacement PID feedback controller. The LSTM controller is trained by using a large number of experimental data of a self-made servo-motor driven uniaxial shake table. After the training is completed, the LSTM controller is implemented for directly generating the command voltage for the servo motor to drive the shake table. Meanwhile, a displacement PID controller is tuned and implemented close to the LSTM controller to prevent the shake table from permanent drift. The control strategy is named the LSTM-PID control scheme. Experimental results demonstrate that the proposed LSTM-PID improves the acceleration tracking performance of the uniaxial shake table for both bare condition and loaded condition with a slender specimen.

• 한국건설관리학회:학술대회논문집
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• 한국건설관리학회 2004년도 제5회 정기학술발표대회 논문집
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• pp.79-86
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• 2004

국내 건설산업의 기술자격제도는 노동부주관 $\ulcorner$국가기술자격법$\lrcorner$ 에 의하여 운영되며, 대표적인 국가자격은 건축사, 기술사 및 기사 등을 들 수 있다. 1990년 중반에 도입된 건설사업관리(CM)는 건설산업을 활성화하기 위한 필수불가결의 조건이 되고 있으나 국가자격으로 공인되지 못하고 있으며, 현안문제로서 가장 시급하다고 판단되는 전문인력 양성은 민간 CM교육기관들의 "공인민간자격"으로서 각각의 교육프로그램과 별도의 인증자격을 가지고 이루어지고 있는 실정이다. 문제는 국제공인자격으로서 신뢰성을 확보하고 있는 유일한 미국CM협회(CMAA)의 "CCM"인증자격과 미국VE협회(SAVE)의 "CVS"인증자격의 사례로 볼 때, 외국에 비하여 CM인증자격이 과다하며, 신뢰성과 효율성을 확보하지 못한 상태로 인증자격자득에게 혼란을 주면서 양산되고 있다는 점이다. 본 고에서는 국내CM인증자격의 문제점을 살펴보고 인증자격의 통합 및 체계화를 통하여 국가공인자격으로 발전하기 위한 개선방안을 제시하고자 한다.

• 한국도로학회논문집
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• 제13권4호
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• pp.167-175
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• 2011

효율적인 도로의 설계와 관리를 위해서는 도로건설의 경제성 분석이 중요하며 이를 위해서는 도로 상태별 차량별 유류소모량의 평가가 필요하다. 도로에서는 초기 건설비용, 유지보수비용, 차량운행비용, 지정체비용 등이 발생되는데, 도로의 경제성 분석을 위해서는 초기 건설비용, 유지보수비용 등과 같은 관리자비용과 차량운행비용, 지정체비용 등과 같은 이용자비용을 모두 포함한 사회적 비용이 고려되어야 한다. 이 중 차량운행비용은 교통량에 따라 그 비용이 변화되므로 차량운행비용 항목의 큰 부분을 차지하는 유류소모량 또한 교통량에 따라 변화하게 된다. 그런데 유류소모량은 차량의 주행속도 및 도로포장의 상태, 특히 평탄성에 따라 크게 변화되므로 도로의 경제성 분석을 위한 차량운행비용의 산정을 위해서는 주행차량에 대해 도로 상태에 따른 유류소모량을 평가하여 경제성 분석에 반영해야 할 필요가 있으나 아직 이를 고려하지 못하고 있는 상황이다. 본 연구에서는 국내에서 운행되는 승용차에 대해서 도로 상태별 유류소모량 추정모델을 개발하였다. 우선 우리나라의 교통시설 투자평가 및 도로건설의 예비타당성 조사에서 차량운행비용 산정을 위해 사용되고 있는 주행속도와 유류소모량의 관계식을 고찰하고, 승용차를 대상으로 도로포장의 평탄성에 따른 유류소모량 변화의 관계를 실제 도로에서 실측하여 평탄성과 유류소모량 변화의 관계를 분석하였다. 실험 결과, 평탄성에 따른 유류소모량의 변화는 평탄성이 1m/km 증가하였을 경우 100km 주행시 약 $80m{\ell}$ 정도의 비율로 유류소모량이 증가하는 것으로 확인되었다. 따라서 도로의 설계 및 유지관리에 있어서 보다 정확한 경제성 분석을 수행하기 위해서는 도로포장의 평탄성에 따른 유류소모량 변화를 고려해야 할 필요가 있다.