• Journal of Korea Water Resources Association
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• 제48권3호
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• pp.149-158
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• 2015

It is well known that emergency outlet works have to be provided for the safety of dams. However, concept of emergency outlet works did not applied for the design of the most dams in Korea. Korean design standard for low-level outlet works does not provide enough design criteria which could be used in design of emergency outlet works. In this research, as-built status and hydraulic design criteria of outlet works, such as drawdown rate or hydraulic pressure due to the impounded water depth, were examined. Another relationship between drawdown rate and the dam slope stability was also examined with SEEP model. It was found that 25% reduction of impounded water depth decreases the pressure forces about 50%. Therefore, outlet works should be designed to drawdown properly at the beginning of the emergency. Seepage analysis of dam bodies showed that most of Korean dams could safely stand for 1m/day drawdown rate. Higher drawdown rate could result high discharge so the drawdown rate must be related with the flood risk of downstream. Finally, multi-stage design was recommended that faster discharge for the initial 25% of water depth in 7-10 days than the rest of it in 1-2 months.

• Proceedings of the Korean Institute of Building Construction Conference
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• 한국건축시공학회 2015년도 추계 학술논문 발표대회
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• pp.66-67
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• 2015

This study compared and analyzed the job importance that site managers perceived by dividing the study scope into customized and expansion remodeling projects and deriving the job descriptions from previous studies. As a result, a total of 7 construction stages and 53 job descriptions were derived. As job importance in customized remodeling projects, removal and demolition works were the most important, followed by preliminary survey, and repair and reinforcement works. In addition, as job importance in expansion remodeling projects, preliminary survey is the most important, followed by civil engineering work, and repair and reinforcement works. It is considered that the job importance of the remodeling projects derived in this study will contribute to improving their job efficiency in the future.

• Journal of the Korean Society of Safety
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• 제35권1호
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• pp.70-78
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• 2020

Nitrox diving was introduced by the NOAA (National Oceanic and Atmospheric Administration) to increase the oxygen content and lower the nitrogen content in respiratory gases. The commercial diving sector specializing in underwater operations has recently introduced regulations on the use of Nitrox. Because the respiratory gas for Nitrox diving has a lower nitrogen content than the normal air, the amount of nitrogen dissolved in the body is small, which not only significantly reduces the decompression time compared to air diving, but also reduces the chance of exposure to decompression sickness. In this study, we applied the VPM (Varying Permeability Model) algorithm to virtual diving with air and Nitrox as a respiratory gas, respectively, to study the optimal Nitrox diving for the safety at the underwater works. The results showed that Nitrox diving had a longer NDL (No-Decompression Limit), a much shorter depression time. In other words, Nitrox diving in underwater works is safer from decompression sickness than commonly used air diving.

• International conference on construction engineering and project management
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• The 1th International Conference on Construction Engineering and Project Management
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• pp.996-1001
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• 2005

Today, government is no longer considered the sole provider of public works or services. Public-Private Partnership (PPP) has been recognized as an important approach to solving problems for governments in providing public works and services. However, the joint ownership of public works/services complicates the administration of PPP projects. Particularly, the fact that government may rescue a distressed project and renegotiate with the developer causes serious problems in project procurement and management. This paper aims to study when and how government will rescue a distressed project and what impacts government's rescue behavior has on project procurement and contract management. A game-theory based model for government rescue will be developed. This pilot study, the author hopes, may provide theoretic foundations to practitioners/policy makers for prescribing creative PPP procurement and management policies and for examining the effectiveness of PPP policies.

• Structural Engineering and Mechanics
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• 제30권6호
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• pp.651-664
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• 2008

The purpose of this study is to develop a rehabilitation technique for heavily earthquake damaged masonry buildings. A full scale one storey masonry building with window and door openings was manufactured and tested on the shock table by applying increased amplitude free vibration up to the point where heavy earthquake damage was observed. Damaged test building was rehabilitated with vertical and diagonal steel straps and then tested again. The effectiveness of improvements obtained by the rehabilitation technique was investigated. Steel straps improved the lateral strength and stiffness of masonry walls and limited the lateral displacement of building. Stability of the masonry walls were also improved by the steel straps. Steel straps reduced the natural period of the earthquake damaged masonry building and prevented the failure of the building at the same amplitude of free vibration.

• Steel and Composite Structures
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• 제25권3호
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• pp.257-270
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• 2017

In this article, an efficient and simple refined theory is proposed for buckling analysis of functionally graded plates by using a new displacement field which includes undetermined integral variables. This theory contains only four unknowns, with is even less than the first shear deformation theory (FSDT). Governing equations are obtained from the principle of virtual works. The closed-form solutions of rectangular plates are determined. Comparison studies are carried out to check the validity of obtained results. The influences of loading conditions and variations of power of functionally graded material, modulus ratio, aspect ratio, and thickness ratio on the critical buckling load of functionally graded plates are examined and discussed.

• Proceedings of the Korean Geotechical Society Conference
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.897-903
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• 2004

Waste lime used in this study is producted as a by-product in the manufacturing process of making $Na_2CO_3$ from local chemical factory in Incheon. Currently about 320 millon tons of waste lime are accumulated and annually 100,000 tons are producted. Reuse of waste lime mixed with soil for banking and backfill materia in civil works was analysed in this study. This study was Carried out to investigate the geotechnical and environmental characteristics on field application. Field investigations were conducted on the road construction site in Incheon. This study presents the results of the engineering characteristics in field test and the leaching characteristic of waste lime in laboratory column tests. Countermeasure for reduction of environmental effects was suggested from the test results.

• International Journal of Concrete Structures and Materials
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• 제3권2호
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• pp.127-131
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• 2009

Strengthening and repair of concrete structures using externally bonded fiber reinforced polymer (FRP) composite sheets has been popular around the world during the last two decades. However, premature failure due to debonding of the FRP is one of the important issues still to be resolved. Numerous research studies have dealt with the debonding problem in terms of Effective Bond Length (EBL), however, determination of this length has not yet been completely assessed. This paper summarizes previous works on the EBL and proposes a new relationship of the EBL with the FRP stiffness based on the existing experimental data collected in this study.

• Structural Engineering and Mechanics
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• 제67권3호
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• pp.291-300
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• 2018

In this work, a new trigonometry theory of shear deformation is developed for the static analysis of thick isotropic beams. The number of variables used in this theory is identical to that required in the theory of Euler-Bernoulli, sine function is used in the displacement field in terms of the coordinates of the thickness to represent the effects of shear deformation. The advantage of this theory is that shear stresses can be obtained directly from the relationships constitute, while respecting the boundary conditions at the free surface level of the beam. Therefore, this theory avoids the use of shear correction coefficients. The differential equilibrium equations are obtained using the principle of virtual works. A thick isotropic beam is considered, whose numerical study to show the effectiveness of this theory.

• Journal of Engineering Education Research
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• 제9권4호
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• pp.5-9
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• 2006

In this research, a case study for cooperative learning practiced in a design class for environmental engineering was presented. Designing a treatment facility for urban diffuse pollution was a main problem given to the participants. Turn-key system for civil works were simulated throughout class works. Twenty five students were grouped into four virtual companies and assigned own position from chairperson to workers. Each group competed throughout establishing design concept regarding order, expense calculation, process distribution, actual calculation. Best design with lowest bidding won the first place. For evaluating class effectiveness, one student from each group were monitored thorough semester. Participants were improved for their understanding about company establishment, turn-key system management, awareness about personal management, and presentation skills. Tension of the class was effectively elevated as well.