• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.1
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• pp.79-89
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• 2023

The inventory of many materials requires a large storage space, and the longer the storage period, the higher the potential maintenance cost. When materials are stored on a construction site, there are also concerns about safety due to the reduction of room for movement and working. On the other hand, construction sites that do not store materials have insufficient inventory, making it difficult to respond to demands such as sudden design changes. Ordering materials is then subject to delays and extra costs. Although securing an appropriate amount of inventory is important, in many cases, material management on a construction site depends on the experience of the site manager, so a reasonable material inventory management plan that reflects the construction conditions of a site is required. This study proposes an economical material management method by reflecting variables such as the status of the preceding and following activities, site size, material delivery cost, timing of an order, and quantity of orders. To this end, we set the appropriate inventory amount while adjusting related activities in the activity network, using float time for each activity, the size of the yard, and the order quantity as the main variables, and applied a genetic algorithm to this process to suggest the optimal order timing and order quantity. The material delivery cost derived from the results is set as a fitness index and the efficiency of inventory management was verified through a case application.

• Journal of the Korea Concrete Institute
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• v.23 no.4
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• pp.441-448
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• 2011

In this study, experimental tests of chemical and autogenous shrinkage were performed to evaluate the early age shrinkage behaviors of ultra high performance cementitious composites (UHPCC) with various replacement ratios of silica fume (SF), shrinkage reducing agent (SRA), expansive admixture (EA), and superplasticizer (SP). Starting time of self-desiccation, was analyzed by comparing the setting times and the deviated point of chemical and autogenous shrinkage strains. The test results indicated that both SF and SRA augment the early age chemical shrinkage, whereas SP delays the hydration reaction between cement particles and water, and reduces chemical shrinkage. About 49% of autogenous shrinkage was depleted by synergetic effect of SRA and EA. The hardening of UHPCC was catalyzed by containing EA. Self-desiccation of UHPCC occurred prior to the initial setting due to the high volume fraction of fibers and low water-binder ratio (W/B).

• Journal of the Korean Geosynthetics Society
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• v.9 no.2
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• pp.1-9
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• 2010

At present, the sand mat method is actively used for improvement of soft ground. But, there are some problems related with sand mat which has been used as a way to accelerate consolidation settlement. First of all, insufficiency of sand due to imbalances in market supply and demand is the one of the biggest problems, which makes price high of sand and delays a term of total construction work. Moreover, it is necessary to preserve integrity of environment from natural disruption caused by indiscreet quarrying and dredging operation to supply sand for soil improvement construction site. This paper presents the feasibility study to use of Precious Slag Ball instead of sand mat as the replacing material through the basic soil property tests, the medium of discharge capacity test and analysis of settlement property. It is also evaluates the performance of Precious Slag Ball as a sand mat in terms of discharge capacity, ground settlement by the K-Embank program based on field experimental work.

• Journal of the Korea Institute of Building Construction
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• v.16 no.3
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• pp.193-199
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• 2016

This study is a research about performance of fireproof board using industrial waste such as oyster shell and dry process bottom ash through the heating test and conclusions were obtained as follows. Test samples show back side temperatures as follows : in $300^{\circ}C$, $103.1{\sim}125.1^{\circ}C$, in $600^{\circ}C$, $201.1{\sim}210.1^{\circ}C$, in $900^{\circ}C$, $249.2{\sim}276.9^{\circ}C$. In the test, temperature increases of specimens of fireproof board are kept at certain temperatures hence it could be concluded that the specimens withstand high temperatures. According to the test, it could be concluded that fireproof board made by smaller particles shows better performance up to $600^{\circ}C$ while at higher temperatures, fireproof board made by bigger particles shows better performance. It is estimated that fireproof board made by particles of bigger size has more pore structure and it delays heat conduction.

• The Journal of Engineering Geology
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• v.25 no.2
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• pp.273-280
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• 2015

Delays in horizontal well drilling when encountering heterogeneous sediments can have negative effects on the construction process at a riverbank filtration site. Grain size analysis, including calculation of the coefficient of uniformity and the coefficient of curvature, was conducted on soil samples collected at each drilling depth during the process of drilling horizontal wells. These results were then used to develop a linear equation for estimating drilling velocity using the coefficient of uniformity and the coefficient of curvature as inputs. Testing of the linear equation in other horizontal wells indicates that the equation is most appropriate for coarse-sand-sized and well-sorted sediment. Because this study was conducted in a region with small- to medium-sized streams, more data are needed from larger rivers to modify the general equation. Our results will provide better estimates of drilling velocity, in turn enabling more detailed design and more effective construction management at riverbank filtration sites.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.5B
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• pp.274-286
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• 2005

In this paper, we propose a new power-efficient and reliable connected dominating set based routing protocol in the mobile ad hoc networks. Gateway nodes must be elected in consideration of residual energy and mobility because frequent reconstruction of connected dominating set result in transmission error for route losses. If node density is high, it results in a lot of contentions and more delays for network congestion. Therefore, in this paper, we propose a new construction method of connected dominating set that supports reliable and efficient data transmission through minimizing reconstruction of connected dominating set by delaying neighbor set advertisement message broadcast in proportion to weighted sum of residual energy, mobility, and the number of neighbor nodes. The performance of the proposed protocol is proved by simulation of various conditions.

• Korean Journal of Construction Engineering and Management
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• v.12 no.3
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• pp.22-30
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• 2011

In the planning phase of domestic urban environment maintenance and improvement projects, a particular problem is the increase in service expenses and project cost with the establishment of plans under circumstances that exclude the residents or have incomplete consent from them and the public organization. This delays the promotion of the project. This study aims to resolve such problems by proposing a measure to introduce a privatepublic consultative body for residents and the relevant departments of the public sector, to encourage them to participate and establish plans together from the beginning. This is expected to contribute to the smooth promotion of the project, as it would remove the conflicting factors that are expected to be generated in the project implementation phase before they could emerge.

• Geomechanics and Engineering
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• v.17 no.5
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• pp.453-464
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• 2019

Soft marine soil has high fine-grained soil content and in-situ water content. Thus, it has low shear strength and bearing capacity and is susceptible to a large settlement, which leads to difficulties with coastal infrastructure construction. Therefore, strength improvement and settlement control are essential considerations for construction on soft marine soil deposits. Biopolymers show their potential for improving soil stability, which can reduce the environmental drawbacks of conventional soil treatment. This study used two biopolymers, an anionic xanthan gum biopolymer and a cationic ${\varepsilon}-polylysine$ biopolymer, as representatives to enhance the geotechnical engineering properties of soft marine soil. Effects of the biopolymers on marine soil were analyzed through a series of experiments considering the Atterberg limits, shear strength at a constant water content, compressive strength in a dry condition, laboratory consolidation, and sedimentation. Xanthan gum treatment affects the Atterberg limits, shear strength, and compressive strength by interparticle bonding and the formation of a viscous hydrogel. However, xanthan gum delays the consolidation procedure and increases the compressibility of soils. While ${\varepsilon}-polylysine$ treatment does not affect compressive strength, it shows potential for coagulating soil particles in a suspension state. ${\varepsilon}-Polylysine$ forms bridges between soil particles, showing an increase in settling velocity and final sediment density. The results of this study show various potential applications of biopolymers. Xanthan gum biopolymer was identified as a soil strengthening material, while ${\varepsilon}-polylysine$ biopolymer can be applied as a soil-coagulating material.

• Journal of the Korean Institute of Gas
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• v.25 no.6
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• pp.85-91
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• 2021

In January 2019, the Korean government announced the 「Hydrogen Economy Activation Roadmap」 to be a world-class leading country in Hydrogen economy. Korea has established a strategy that can lead the hydrogen economy with its strong points of 'hydrogen car' and 'fuel cell'. As a part of that, a target of supplying hydrogen vehicle charging stations to 310 by 2022 and 1,200 by 2040 was established. In line with this, Korea Gas Safety Corporation will operate a pre-consulting system of hydrogen vehicle charging station in February 2021 to solve in advance construction delays due to various on-site problems according to safety standards during the construction stage to build a hydrogen refueling station with a sense of speed. This paper is to find out about the pre-consulting system and to analyze its effects.

• Journal of the Korean Geotechnical Society
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• v.36 no.10
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• pp.5-19
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• 2020

With increasing demand for offshore structures, the demand for temporary structures to help the offshore construction work has increased. A cofferdam is a temporary barrier to stop the inflow of water in the construction site and allows working in the dry condition when the construction is done within the water. However, it is a major cause of construction delays and increased costs because additional works are required to block the water inflow. Recently, in order to overcome the limitations of the conventional cofferdam methods and to increase economic efficiency, a large-diameter steel cofferdam method has been proposed which can be installed quickly in the seabed by using the suction pressure. In this circular steel cofferdam method, the top side of the cofferdam including the top-lid is always exposed above the sea level in order to use it as a water barrier, unlike the conventional suction bucket foundation. After installation, the top-lid of the cofferdam is removed and the water filled inside the cofferdam is discharged to make the interior dry condition. In this study, the circular steel cofferdam with a 5 m inner diameter was fabricated and the installation tests were conducted at the Saemaguem test site. During the experiment, variation of suction pressure, leakage between connections, structure deformation, and inclination of the steel cofferdam were measured and post-analyzed. This study verified the new circular steel cofferdam method and confirmed that the suction installation method can be successfully used for various purposes on offshore structures.