• Journal of the Korea Institute of Building Construction
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• v.11 no.1
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• pp.9-17
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• 2011

Project delay is one of the most crucial impact factors in the construction process from a schedule and cost management perspective. This study focused on analyzing the causes of concrete frame work delay in the apartment construction project. According to the analysis of project cost composition, the direct cost of concrete works was highest in most samples. Actual delays of concrete works were analyzed for the six different construction components. Causes of delay were grouped into two categories; preconstruction and construction phases and these two groups were further divided into sub-groups. Analysis results revealed that the most significant delay was occurred in the 1st. floor concrete skeleton work. For each delay factor, implications of delay as well as suggestion(s) for reducing the possibility of schedule delay are provided.

• 한국정보통신설비학회:학술대회논문집
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• 2004.08a
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• pp.230-233
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• 2004

현재 KT의 관로포설 공법은 관 상부 토피 1m를 확보한 상태에서 차량하중이 작용한다는 가정하에서 제정된 것이며, 토피 1m를 확보하지 못하는 구간에는 별도의 보강공법을 적용하고 있다. 그러나 현재 관로공사의 대부분을 차지하는 도로유관공사는 도로 조성이 종료되는 시점에는 토피 1m를 확보하지만, 도로조성 공사기간 중에는 별도의 보강공사 없이 토피 60cm 내외에서 공사 차량의 하중이 관로에 그대로 전달되고 있어 관로의 찌그러짐 현상이 발생하고 있다. 본 논문은 이와 같은 조건에서도 고품질의 관로를 확보하기 위하여 현행 FC관로 뿐만 아니라 지하매설관으로 사용되는 각종 재질의 관에 대한 특성을 검토하였으며 매설관 변형실험을 통하여 도로유관공사에 적합한 관로재질을 제시하였다.

• Journal of the Korean GEO-environmental Society
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• v.21 no.8
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• pp.5-13
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• 2020

During the construction of underground space expansion of old facilities, it is necessary to secure temporary residence space for existing residents as well as noise and vibration issues during construction, and in the case of commercial, industrial, and social use, damage is expected from suspension of the use of facilities. There is a need for a technology that minimizes noise and vibration during underground expansion, enabling the use of existing facilities even during construction. In this study, a practical underground extension model is proposed by analyzing the behavior of the temporary structure and the surrounding ground as a result of measurement at each construction stage for a actual construction site. In order to solve the problems that occurred during construction, the basement slabs were placed in advance after the initial excavation. The measurement results (building inclinometer, crack measurement system, structure inclinometer and surface settlement meter) at the site were reviewed to analyze the behavior of the temporary structure and surrounding ground. As a result, it was confirmed that the inclinometer of the building and the structural inclinometer showed a tendency that the displacement after the slab line was placed was reduced or converged. The placement of basement slabs during underground extension not only relived the noise and vibration problems during construction, but also secured the stability of structures.

• Korean Journal of Environment and Ecology
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• v.20 no.2
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• pp.235-258
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• 2006

The monitoring of vegetation and water quality before(2003), during(2004) and after(2005) the restoration work of Cheonggye Stream indicated that $BOD_5$ concentration before the project averaged 51.1mg/L and that both the inflow of water from Hang River and the funnel of subway station water into the stream lowered the $BOD_5$ to 3.3mg/L, improving its water quality to the third grade. Species of plants slightly increased from 121 to 132 after the restoration. Specifically, perennial plant comprised 35.6%, an increase from 24.8% recorded before the restoration. Phragmites communis and Zoysia japonica communities were observed as the introduction vegetation. However, Humulus japonicus and Erigeron canadensis communities, which were classified into the first grade according to the vegetation conservation classification, were found to be still prevailing though they were dominant community before the restoration, meaning that the ecological condition of plants had not changed very significantly. An the other hand the water quality of the reference reach was classified into the first grade based on $BOD_5$, which implies the water quality of the section was better than the project reaches. Besides the section had more diverse plant species which numbered 154, and furthermore, the rate of immigrated plants comprised 13% which was lower than 28.8% recorded by the project sections. The project reaches are considered to be inferior to the reference section in terms of ecological condition. The effectiveness of the stream restoration cannot be determined only by such short-term investigation as was conducted in this study, and it is considered that the effectiveness of the restoration of Cheonggye Stream can be determined only if investigations in other major factors are conducted over the long-term period.

• Water for future
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• v.56 no.6
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• pp.76-83
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• 2023

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.6
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• pp.1145-1152
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• 2016

A construction post evaluation is introduced to provide information that can be used for similar construction projects in the future through the evaluation of the efficiency of a public construction project and the verification of the appropriateness of the project results. However, it is not widely used due to a lack of awareness of the method. For this reason, the aim of this study is to provide a basic frame that can be utilized as a reference for a similar project in the future based on the construction post evaluation. More specifically, a more effective analysis method for the construction post evaluation is proposed and then an exemplary analysis is performed based on the method. The paper analyzes 293 cases stored in construction CALS. Construction cost growth rates of railway projects are tend to be greater than other project types like highway, expressway, and harbour. Then, construction schedule grwoth rates of expressway are greater than others. This is expected to provide useful information for a future project, and serve as a basic frame. Moreover, it is also meaningful that a project can be analyzed from different perspectives through the construction post evaluation.

• Korean Journal of Construction Engineering and Management
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• v.15 no.5
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• pp.94-102
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• 2014

This study analyzes necessity of expanding construction insurance and estimates required budget. Construction insurance is obliged by National Contract Law and Local Contract Law to protect projet owners and contractors from any unexpected construction risk such as financial losses in construction process. Currently the contracts of design-build and alternate-bid projects as well as PQ project, which are greater than 20 billion won, require the contractors to provide construction insurances in Korea. Insurance premiums are borne by the public project owner. Those contractors whose contract volume is less than 20 billion won burden all risks of projects at their cost. This causes equity problem. Because small-and-medium contractors are discriminated against large contractors since insurance-obliged projects are performed by large contractors and insurance premiums are borne by the public project owner. On the other hands, in all engineering projects, regardless of volume, insurance premiums are borne by the project owner. Therefore current regulation has to be improved, by expanding to all public projects. The average ratio of unobliged projects is 46%, in recent 3 years, prime cost of insurance companies is estimated 0.2%. Moreover considering risks of each construction type, prime cost of unobliged works is estimated as 0.13%. Hence additional necessary budget is estimated to be 2.09 billion won if total volume of public work is 3.5 trillion won. And 2.39 billion won is derived if total volume of public projects is 4 trillion won.

• Journal of the Korea Institute of Building Construction
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• v.17 no.6
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• pp.577-585
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• 2017

HPC method is developing to improve the constructability and structural performance of the existing PC method. The objective of this study is to develop construction procedures and to analysis of construction period for HPC method. In order to develop construction procedures, the building construction data of the existing half-slab method was analyzed. Analyzing design drawings and specifications of nine construction cases, a prototype of half-slab method, was drawn. Applying the core technology of HPC method to the drawn prototype of half-slab method, a prototype of HPC method, was developed. The differences of both methods were 'installing PC column' and 'placing topping concrete'. To analysis the differences of both methods, seven construction cases were analyzed. According to the analysis for HPC method, cases1 and 2 had columns divided for construction shortened about 16% of a construction period. The schedule of column assembly work was analyzed to be shortened much. That is judged to be because the use of a hollow PC column leads to a decrease in the number of columns. In particular, if HPC method is applied to a building construction site using large columns, it is analyzed to shorten a construction period more than the existing Half-slab method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.05a
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• pp.300-302
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• 2022

In this paper, We propose a mobility model-based resource collision avoidance technique that can share radio resources without resource collision between UAV in a FANET environment. The proposed technique tries to reduce the occurrence of resource collisions by estimating UAV mobility based on information obtained from GPS devices installed in UAV. Through simulations, The performance was compared with the contention-based protocol, and it was confirmed that the proposed algorithm can reduce resource collisions.

• Korean Journal of Construction Engineering and Management
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• v.15 no.5
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• pp.49-60
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• 2014

Electrical construction cost index has been applied fixed-weighted method. But fixed-weighted method can't faithfully reflect industrial structure changes. Because the weighted value and price index of fixed-weighted method is fixed on the basic period. Electrical construction cost index is composed of the cost of labor and material. So it fluctuates sharply whenever the construction association of korea announces the laborer's wage of electrical construction. And it depends on only the producer price index changes that is related to electrical construction since then. So a study is focused on developing electrical construction cost index applied chain-weighted method. Because chain-weighted method can reflect the realities of the electrical construction and alleviate the sudden changes of labor cost with link index. We verify that chain-weighted method relieves the step states of electrical construction cost index applied fixed-weighted method.