• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2008.11a
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• pp.334-339
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• 2008

Construction that over 70% of the structure consists of concrete gets bigger and higher gradually and the demand of that is increasing as well. However, it's not easy to supply young and skilled persons on construction site because of social avoidance phenomena about 3D occupation, so it causes serious problems like aging and shortage of technicians. To solve the problems, executives related to the construction field make a management effort in various ways such as construction period shortening, labor productivity improvement and good quality but recently, they have an increasing interest in the necessity of the modularization of the high-rise building and the automation of the engineering development for the strengthening of international competitive power as more active and long-term alternatives. Therefore, this study is to propose the roadmap in order to make lots of efforts in developing construction technologies of high-rise buildings by performing a foundation study, the strategy for 4-step research development, on modularized construction system of concrete structure of high-rise buildings through domestic and foreign preceding research analyses associated with optimal design modularization technique, module factory automation and assembly automation of modularized objects.

• Journal of the Korean Geotechnical Society
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• v.29 no.11
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• pp.119-127
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• 2013

Recently, several researches on the development of new economical foundation types have been performed to support floating structures as many offshore structures have been constructed. This study focused on the evaluation of bearing capacity of group suction piles, which are connected by a concrete pile cap. The offshore floating structures are mainly subjected to horizontal loading, so the horizontal bearing capacities of the group suction piles were analyzed by performing 3-dimensional finite element analyses. The group suction piles are expected to behave as a rigid pile due to its shallow embedded depth. Therefore, the detailed soil modeling was necessary to simulate the bearing behavior of soils under low confining pressure. The modulus and the strength of soils were modelled to increase with effective confining pressure in soils. For the parametric study, the center-to-center spacing between piles was varied and two soil types of clay and sands were applied. The analyses results showed that the yielding load of the group pile increased with the increase of the pile spacing and the yielding load of the group piles with 5D spacing was about 3 times larger than that of the single pile with free rotation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.2
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• pp.501-514
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• 2015

Earthwork is a basic operation for all forms of civil works and affects construction time, cost and productivity. It is a mechanized operation that needs various construction equipment as a group and uses a lot of fuel for construction equipment. But, the problem is that earthwork operation is usually performed by equipment operator's heuristic and intuition, which can cause low productivity, high fuel consumption, and high carbon dioxide emission. As one of solutions for this problem, the fleet management system for construction equipment is suggested for effective earthwork planning, optimal equipment allocation, efficient machine operation, fast information exchange, and so forth. The purpose of this research is to suggest core methods for developing the equipment fleet management system. The methods include 3D solid parametric model generation, soil distribution using Cctree data structure, equipment fleet construction and equipment fleet operation. A simulation test is performed to verify the effectiveness of the equipment fleet management system in terms of equipment operating ratio, fuel usage, and $CO_2$ emission.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.1
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• pp.143-149
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• 2016

This study evaluated the shear behavior of geogrid reinforced ballast material using a large scale direct shear test and discrete element method (DEM) based on PFC 3D program. The direct shear test was conducted on ballast materials that have different particle size distributions. Whereas the test results revealed that the shear strength generally increased with the larger particle size of ballast material without geogrid reinforcement, the shear behavior of ballast material was found to change pertaining to the relationship between particle size distribution and geogrid rib size. Generally, it is deemed the effectiveness of reinforcement can be achieved when the rib size is two times greater than average particle size. A numerical analysis based on DEM was conducted to verify the test results. The geogrid modeling was successfully completed by calibration process along with sensitivity analysis to have actual tensile strength provided by manufacturer. With a given geogrid model, the parametric evaluation was further carried out to examine the interactive behavior between geogrid and ballast material. Consequently, it was found that the effectiveness zone of geogrid reinforcement generated within a specific depth.

• Ocean Systems Engineering
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• v.1 no.4
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• pp.285-296
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• 2011

Spar platforms have several advantages for deploying wind turbines in offshore for depth beyond 120 m. The merit of spar platform is large range of topside payloads, favourable motions compared to other floating structures and minimum hull/deck interface. The main objective of this paper is to present the response analysis of the slack moored spar platform supporting 5MW wind turbine with bottom keel plates in regular and random waves, studied experimentally and numerically. A 1:100 scale model of the spar with sparD, sparCD and sparSD configuration was studied in the wave basin ($30{\times}30{\times}3m$) in Ocean engineering department in IIT Madras. In present study the effect of wind loading, blade dynamics and control, and tower elasticity are not considered. This paper presents the details of the studies carried out on a 16 m diameter and 100 m long spar buoy supporting a 90 m tall 5 MW wind turbine with 3600 kN weight of Nacelle and Rotor and 3500 kN weight of tower. The weight of the ballast and the draft of the spar are adjusted in such a way to keep the centre of gravity below the centre of buoyancy. The mooring lines are divided into four groups, each of which has four lines. The studies were carried out in regular and random waves. The operational significant wave height of 2.5 m and 10 s wave period and survival significant wave height of 6 m and 18 s wave period in 300 m water depth are considered. The wind speed corresponding to the operational wave height is about 22 knots and this wind speed is considered to be operating wind speed for turbines. The heave and surge accelerations at the top of spar platform were measured and are used for calculating the response. The geometric modeling of spar was carried out using Multisurf and this was directly exported to WAMIT for subsequent hydrodynamic and mooring system analysis. The numerical results were compared with experimental results and the comparison was found to be good. Parametric study was carried out to find out the effect of shape, size and spacing of keel plate and from the results obtained from present work ,it is recommended to use circular keel plate instead of square plate.