• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.989-992
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• 2008

In this paper, we are presenting a case that integrates ultra high strength concrete(150MPa) with surface-exposed concrete. Ahead of the field application, we carried out laboratory experiment and B/P Test for a basic property of concrete(slump flow, air content, 50cm flow time, elapse time change and compression strength) and productivity. The next, we conducted Mock-up Test using simulation specimen to evaluate infilling, surface-finishing and hydration heat of concrete. We had satisfactory results for a basic property and hydration heat of concrete. However at the time of field application, it was occurred rupture of formwork because of high lateral pressure of concrete, and then formwork was reinforced and case-in-place time was adjusted. And regardless of low and high frequency vibration, it occurred to surface-pockmark. In case that applies ultra high strength concrete to surface-exposed concrete, we estimate that it is important of systematic management and improvement of construction.

• Journal of the Society of Disaster Information
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• v.8 no.2
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• pp.119-137
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• 2012

In this study, the damages and condition of road pavement were analyzed using pavement management system (PMS) for the structural improvement. Problems of road pavement management were issued by in-depth interview with workers in charge of plant, construction and supervision. By surveying advanced road pavement management, the way how to improve road pavement management in Seoul was discussed. In conclusion, it is necessary to take measures against road heavy traffic and heavy rain in summer. It was found that the problem of early damages of road pavement due to uniform layout with analyzing life cycle cost (LCC). According to the results of survey, it was suggested to strength practical training and to control precisely the temperature of pavement in the process of production and construction.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.1
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• pp.41-49
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• 2021

3D printing techniques have been recently adopted in the construction industry. It mainly utilizes additive manufacturing which is the fabrication process depositing successive layers of materials without any formworks. Conventional cementitious materials may not be directly applicable to 3D printing because 3D printable cementitious materials is required to satisfy such characteristics as pumpability, extrudability, and buildability in a fresh state. This study aimed to investigate rheological properties and required performances of 3D printable cementitious materials, by reviewing existing studies. Test methods and equipments, evaluation results and characteristics of mixture additives were compared. Based on reviews of existing studies, this study indicates that the viscosity is mainly relevant to the pumpability of 3D printable materials whereas the yield stress and thixotropy are important in securing buildability of the materials.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.545-552
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• 2020

This study evaluated the support performance of fiber-net integrated shotcrete in tunnel support system developed for the purpose of improving constructability and stability while fully performing its mechanical performance as a tunnel support materials by four-point bending test, two-dimensional numerical analysis, and cross-sectional analysis. As a result of evaluating the flexural performance through a four-point bending test, in the case of fiber-net reinforced shotcrete, the tensile performance of fiber-net resulted in a continuous increase in load after crack occurrence, unlike steel fiber reinforced shotcrete. Also, the results of the tunnel cross-sectional structure analysis for ground conditions and the cross-sectional analysis of fiber-net and steel fiber reinforced shotcrete showed that sufficient support performance can be exhibited even if the thickness of fiber-net reinforced shotcrete was reduced compared to the previous one. Additionally, through these results, the support pattern of fiber-net integrated shotcrete in tunnel support system, which can be applied efficiently to the construction sections requiring higher stability among the rock mass class III, was proposed.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2012.04a
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• pp.155-158
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• 2012

$CO_2$ 소화설비는 방호구역 내 적절한 설계농도를 확보하고 또한 일정 시간 유지해 주어야 충분한 소화성능을 발휘할 수가 있다. 따라서 시공 후에도 $CO_2$ 소화설비의 성능을 주기적으로 확인이 필요하다. 석유화학플랜트나 원자력발전소와 같은 국가 중요위험시설은 화재 발생시 대형피해가 발생할 수 있으므로 직접방사시험을 통해 소화성능을 검증할 필요가 있다. 본 연구는 국가 중요위험시설에 설치된 전역방출방식의 $CO_2$ 소화설비 중에서 표면화재 방호구역과 심부화재 방호구역을 각각 선정하여 $CO_2$ 소화설비의 소화성능을 검증해 보았다. 시험결과 표면화재와 심부화재 방호구역 모두 $CO_2$ 설계농도를 확보하고 있음을 확인하였으며, 심부화재의 경우 20분 이상 설계농도가 유지되었다. 본 연구를 통해 직접 방사시험 방법 및 판정방법을 소개하였으며, 국가 중요위험시설에는 직접 방사시험을 통한 소화설비 신뢰성 검증의 필요성을 제기하였다.

• Journal of the Korea Institute of Building Construction
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• v.11 no.2
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• pp.145-153
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• 2011

Since the early 1990s, Korean construction companies have strived to evolve into global Engineering Construction (EC) companies. However, such efforts have been unsuccessful, partly due to a lack of clear objectives and a misunderstanding of the direction that needed to be taken for such a change. A better understanding is required with respect to the need to transform into an EC company in the context of the rapidly changing global construction environment. This research investigates major EC companies from around the world, and assesses the status of domestic companies' efforts for EC transition. The results of these investigations revealed that domestic firms need to better prioritize their strengths for different markets, i.e., decide whether to implement directly, outsource or limit to process management. In addition, the investigations showed that the global market is shifting from monolithic projects to more complex projects. Such projects require firms with the ability to develop and implement high front-end investment strategies, planning capabilities, and pre-design management skills. Accordingly, we recommend that firms differentiate themselves by developing such a skill set required for specific products.

• Journal of the Korean Geosynthetics Society
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• v.21 no.4
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• pp.21-29
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• 2022

The room-and-pillar method or grid-type underground space is a method of forming a space by excavating the excavation part at regular intervals so that it is orthogonal and using natural rock mass as a structure. Such excavation may appear different in size from the excavation stage where the maximum displacement occurs depending on the excavation direction and sequence. In this study, considering the installation of support materials such as shotcrete and rock bolts for the optimal design of the excavation process, the safety and constructability of the design and construction of the grid-type underground space under specific ground conditions were analytically reviewed. The ground conditions were set using an numerical method, and the stress at pillar and displacement at center of room were considered for each excavation stage and construction type under a constant surcharge. The height of the space was 8m, which was set higher than the size of a general office, and was reviewed in consideration of equipment and plant facilities. In addition, the degree of displacement control according to the installation of support materials was reviewed in consideration of shotcrete and rock bolts.

• Journal of the Korea Institute of Building Construction
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• v.22 no.2
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• pp.161-169
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• 2022

The government [3] specifies steel pipe scaffolding as conventional scaffolding and is promoting the installation of system scaffolding, an integrated work platform, and avoidance of the use of steel pipe scaffolding as much as possible. However, in places where equipment cannot enter, such as power plants and plant sites, places the structure is complex, and places where scaffolding cannot be stacked on the ground, there is no choice but to install steel pipe scaffolding. When installing steel pipe scaffolding on an H-beam structure at a high place, the performance of the steel frame clamp is very important in order to form a work space which workers can work safely. In this study, the displacement magnitude and tensile load of members in each installation direction of the clamp for steel frame were verified through performance tests and structural analysis modeling. As a result, it was confirmed that the performance for each installation direction satisfies the safety certification standard tensile load of 10,000N. Although the performance value is satisfactory, deformation of the attachment pressing bolt was verified and was confirmed to have minimal deformation. Thus, to ensure the load is properly to the attachment body, the clamp for a steel frame must be installed in the direction in which the load is transmitted.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.430-439
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• 2019

In this study, a nonlinear impact analysis was performed to evaluate the safety and damage of an eco-pillar debris barrier with a hollow cross-section, which was proposed to improve constructability and economic efficiency. The construction of concrete eco-pillar debris barriers has increased recently. However, there are no design standards concerning debris barriers in Korea, and it is difficult to find a study on performance evaluations in extreme environments. Thus, an analysis of an eco-pillar debris barrier was done using the rock impact speed, which was estimated from the debris flow velocity. The diameters of rocks were determined by ETAG 27. The impact position, angles, and rock diameter were considered as variables. A concrete nonlinear material model was applied, and the estimation of damage was done by ABAQUS software. As a result, the damage ratio was found to be less than 1.0 at rock diameters of 0.3 m and 0.5 m, but it was 1.39 when the diameter was 0.7 m. This study could be used as basic data on impact force in the design of the cross section of an eco-pillar debris barrier.

• Journal of Navigation and Port Research
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• v.47 no.4
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• pp.256-270
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• 2023

In this study, a sliding mode (SM) controller for dynamic positioning (DP) was specifically designed for a turret connection operation of a ship or an offshore structure in which an arbitrary point on the structure could be controlled as the motion center instead of the center of mass. The SM controller allows control of the arbitrary point and provides capability to manage uncertainties in the dynamics of ships and offshore structures, external forces caused by unknown changing marine environments, and transient performance of DP systems. The Jacobian matrix included in kinematic equations of the controlled object was modified to design the SM controller to control based on an arbitrary point of ships or offshore structures. To ensure robustness of the controller, the Lyapunov stability theory was applied in the design of the SM controller. In general, for robustness in DP control, gain scheduling based on a proportional-derivative (PD) control algorithm is employed. However, finding appropriate gains for gain scheduling complicates the application of DP systems. Therefore, in this study, the SM control algorithm was considered to mitigate the complexity of the DP controller for ships and offshore structures. To validate the proposed SM control algorithm, time-domain simulations were conducted and utilized to evaluate the performance of the control algorithm. The effectiveness of the proposed SM controller was assessed by comparing simulation results with results of a conventional PD control algorithm applied in DP control.