• IE interfaces
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• v.24 no.1
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• pp.78-86
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• 2011

To mitigate space restriction and to raise productivity, some shipbuilding companies use floating-docks on the sea instead of dry-docks on the land. In that case, a floating-crane that can lift very heavy objects (up to 3,600 tons) is used to handle the blocks which are the basic units in shipbuilding processes, and so, very large blocks (these are called the mega-blocks) can be used to build a ship. But, because these mega-blocks can be made only in the area near the floating-dock and beside the sea, the space is very important resource for the process. Therefore, our problem is to make an efficient spatial schedule for the mega-block assembly yard. First of all, we formulate this situation into a mathematical model and find optimal solution for a small problem using a commercial optimization software. But, the software could not give optimal solutions for practical sized problems in a reasonable time, and so we propose a GA-based heuristic algorithm. Through a numerical experiment, finally, we show that the spatial scheduling algorithm can provide a very good performance.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.2
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• pp.419-425
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• 2017

Managing mega construction project is a very challenging task due to its large scale and complexity. To deal with the challenge, progress measurement must be estimated reliably and effectively. Many researchers have presented progress measurement methods, but previous studies are limited to single or several types of facilities. Thus, they have difficulties to being applied to mega construction projects that covers multiple facilities. To overcome the limitations, this paper proposes a progress measurement framework considering characteristics of mega construction projects. The framework consists of four phases : development of Work Breakdown Structure, determination of weights of main facilities and sub facilities, and calculation of the integrated progress rate. To validate the proposed approach, a case study of Sejong city in Korea was performed. The results of the case study showed the applicability of the proposed framework and confirmed that it enables to reliably measure progress rate of mega construction projects.

• Journal of Navigation and Port Research
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• v.27 no.1
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• pp.49-54
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• 2003

Recently, mega-float offshore structure is studied as of the effective utilization of the ocean space. And mega-float structure are now being considered for various applications such as floating airports. container yard, offshore cities and so on. This mega-float structure is relatively flexible compared with floating structures like large ship. When we estimate dynamic responses of these structures in waves, the elastic deformation is important, because vertical dimension is small compare with horizontal. the analysis of the dynamic reponses as it receive regular wave is studied. The finite element method is used in the analysis of structural section of this model. And the analysis is carried out using the boundary element method in the fluid division. In oder to know the characteristics of the dynamic response of the mega-float structures, effects of wavelength, water depth, and wave direction on the dynamic response of the floating structure are studied by use of numerical calculation.

• Journal of Wetlands Research
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• v.21 no.spc
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• pp.90-97
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• 2019

In recent years, flood due to the consecutive storm events have been occurred and property damage and casualties are in increasing trend. This study calls the consecutively occurred storm events as a mega rainfall scenario and the discharge by the scenario is defined as a mega flood discharge. A mega rainfall scenario was created on the assumption that 100-year frequency rainfall events were consecutively occurred in the Gyeongancheon stream basin. The SSARR (Streamflow Synthesis and Reservoir Regulation) model was used to estimate the mega flood discharge using the scenario in the basin. In addition, in order to perform more reasonable runoff analysis, the parameters were estimated using the SCE_UA algorithm. Also, the calibration and verification were performed using the objective functions of the weighted sum of squared of residual(WSSR), which is advantageous for the peak discharge simulation and sum of squared of residual(SSR). As a result, the mega flood discharge due to the continuous occurrence of 100-year frequency rainfall events in the Gyeongan Stream Basin was estimated to be 4,802㎥/s, and the flood discharge due to the 100-year frequency single rainfall event estimated by "the Master Plan for the Gyeongancheon Stream Improvement" (2011) was 3,810㎥/s. Therefore, the mega flood discharge was found to increase about 992㎥/s more than the single flood event. The results of this study can be used as a basic data for Comprehensive Flood Control Plan of the Gyeongan Stream basin.

• Journal of Navigation and Port Research
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• v.30 no.1 s.107
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• pp.53-59
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• 2006

Recently, 8,000TEU class containerships has started operating the shipping service and the mega-containership of over 10,000TEU is on planning. A unit cost in relation to shipping service is decreased by the bigger ship based on the economy of scale. Most of the previous studies have been performed and focused on the total operation cost from mega port to mega port. However, the purpose of this paper is to estimate economic efficiency of selected hub ports from point of view of total cost such as service cost(or operation cost), port charge and feeder cost, etc. First, the service-network of mega containerships is based on data of a domestic shipping company operated main line and economic analysis of individual scenarios on the cost and traffic when 10,000TEU mega containerships offer the services. The three scenarios presented in this paper set up the hub ports which are the port of Busan, Shanghai and Yokohama The results show that port of Busan is economically the most efficient one among others.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.2 s.54
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• pp.57-68
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• 2007

The mega frame system is becoming popular for the design and construction of skyscrapers because this system exhibits structural efficiency by allowing high rigidity of the structure while minimizing the amount of structural materials to be used. Since the mega frame system is usually adopted for super high-rise buildings, the comfort of occupants may be main concerns in the practical application of this system. For the enhancement of the serviceability of mega frame structures, a semi-active tuned mass damper (STMD) is developed in this study. To this end, a Magnetorheological (MR) damper is employed replacing passive damper as a semi-active damper to improve the control effect of a conventional TMD. Since a conventional finite element model of mega frame structures has significant numbers of DOFs, numerical simulation for investigation of control performances of a STMD is impossible by using the full-order model. Therefore, a reduced-order system using minimal DOFs, which can accurately represent the dynamic behavior of a mega frame structure, is proposed in this study through the matrix condensation technique To improve the efficiency of the matrix condensation technique, multi-level matrix condensation technique is proposed using the structural characteristics of mega frame structures. The efficiency and accuracy of the reduced-order control proposed in this study and the control performance of a STMD were verified using example structures.

• Explosives and Blasting
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• v.23 no.1
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• pp.55-64
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• 2005

Safe and cheap emulsion explosives have recently replaced the existing CD explosives in order for people to reduce the prime cost and to prevent the safety accidents from happening in construction and civil engineering sites. However, the emulsion explosives have been in reality fared with difficulties in terms of the blasting force when using them in the tunnel constructed in the rock mass composed of hard rock. In this regards, this study is to verify their blasting efficiency and possibility of construction by applying MegaMEX, one of the high performance Emulsion explosives, to the rock mass of hard rock. In terms of their blasting efficiency such as advance ratio and fragmentation, it has turned out that they have overcome the limit of the existing Emulsion explosives and they have had the equivalent level of MegaMITE, one of the GD(Gelatin dynamite) types of explosives while they have been also advantageous to the environmental aspects.

• International Commerce and Information Review
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• v.17 no.1
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• pp.289-307
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• 2015

This study was to analyze dynamics of host regional effect in accordance with Mega-events. Yeosu Expo, 2012 was the Mega-event, and dynamic changes in economic indicators such as number of tourists, GRDP, employment rate, and real estate price were analyzed before and after the event. The Mega-event affected positively and increased on the number of tourists. While GRDP affected positively only right before the event, and the employment rate was not significantly affected by the event. The real estate price was increased from the announced time of hosting to the event held, but later decreased. This study suggested the comprehensive method for analyzing the effect of Mega-event and there was a cyclical causality among the result variables.

• Steel and Composite Structures
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• v.45 no.6
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• pp.797-818
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• 2022

Steel-precast ultra-high-performance concrete (UHPC) composite beams with demountable high-strength friction-grip bolt (HSFGB) shear connectors can be used for accelerated bridge construction (ABC) and achieve excellent structural performance, which is expected to be dismantled and recycled at the end of the service life. However, no investigation focuses on the demountability and reusability of such composite beams, as well as the installation difficulties during construction. To address this issue, this study conducted twelve push-out tests to investigate the effects of assembly condition, bolt grade, bolt-hole clearance, infilling grout and pretension on the crack pattern, failure mode, load-slip/uplift relationship, and the structural performance in terms of ultimate shear strength, friction resistance, shear stiffness and slip capacity. The experimental results demonstrated that the presented composite beams exhibited favorable demountability and reusability, in which no significant reduction in strength (less than 3%) and stiffness (less than 5%), but a slight improvement in ductility was observed for the reassembled specimens. Employing oversized preformed holes could ease the fabrication and installation process, yet led to a considerable degradation in both strength and stiffness. With filling the oversized holes with grout, an effective enhancement of the strength and stiffness can be achieved, while causing a difficulty in the demounting of shear connectors. On the basis of the experimental results, more accurate formulations, which considered the effect of bolt-hole clearance, were proposed to predict the shear strength as well as the load-slip relationship of HSFGBs in steel-precast UHPC composite beams.

• Journal of the Earthquake Engineering Society of Korea
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• v.1 no.3
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• pp.29-35
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• 1997

The megastructure combined with the modular concept is an effcient structural system adequate for ultra-tail buildings for the future. An ingeneous structural control system can be developed by separating the internal subframe in one or many modules from the external megaframe, thus taking advantage of the effect of tuned mass dampers without adding any aditional mass. This so called mega-subcontrol system is generally modeled by a 20DF system for parametric study and for finding optimal values of the parameters. In this study the equation of motion for the system is obtained frist and the preconditions for the simplified modeling are investigated. Finally the optimal value for the subsreucture strffness is fomputed with given mass and damping ratios and transfer functions for responses are abtained for white noise ground exitation to verify the effectiveness of the mega-subcontrol system.